diff --git a/applications/test/primitives/Test-primitives.C b/applications/test/primitives/Test-primitives.C
index 0064400290..1fe56e2ae9 100644
--- a/applications/test/primitives/Test-primitives.C
+++ b/applications/test/primitives/Test-primitives.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -346,7 +346,7 @@ int main(int argc, char *argv[])
         is.setScalarByteSize(sizeof(otherType));
 
         Info<< "Stream scalar-size ("
-            << is.scalarByteSize() << ") is native: "
+            << label(is.scalarByteSize()) << ") is native: "
             << Switch(is.checkScalarSize<otherType>()) << nl;
 
 
diff --git a/applications/test/sizeof/Test-sizeof.C b/applications/test/sizeof/Test-sizeof.C
index 78423b0e04..692531acab 100644
--- a/applications/test/sizeof/Test-sizeof.C
+++ b/applications/test/sizeof/Test-sizeof.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -38,6 +38,7 @@ Description
 #include "PstreamBuffers.H"
 #include "argList.H"
 #include "Time.H"
+#include "IOobject.H"
 
 namespace Foam
 {
@@ -132,6 +133,7 @@ int main(int argc, char *argv[])
         cout<<"string:" << sizeof(Foam::string) << nl;
     }
 
+    cout<<"IOobject:" << sizeof(Foam::IOobject) << nl;
     cout<<"IOstream:" << sizeof(Foam::IOstream) << nl;
     cout<<"PstreamBuffers:" << sizeof(Foam::PstreamBuffers) << nl;
     cout<<"Time:" << sizeof(Foam::Time) << nl;
diff --git a/src/OpenFOAM/db/IOobject/IOobject.C b/src/OpenFOAM/db/IOobject/IOobject.C
index e25418fef3..7b0928ebe6 100644
--- a/src/OpenFOAM/db/IOobject/IOobject.C
+++ b/src/OpenFOAM/db/IOobject/IOobject.C
@@ -290,7 +290,8 @@ Foam::IOobject::IOobject
     const objectRegistry& registry,
     readOption ro,
     writeOption wo,
-    bool registerObject
+    bool registerObject,
+    bool globalObject
 )
 :
     name_(name),
@@ -298,14 +299,15 @@ Foam::IOobject::IOobject
     note_(),
     instance_(instance),
     local_(),
-    db_(registry),
     rOpt_(ro),
     wOpt_(wo),
     registerObject_(registerObject),
-    globalObject_(false),
+    globalObject_(globalObject),
     objState_(GOOD),
-    labelByteSize_(sizeof(label)),
-    scalarByteSize_(sizeof(scalar))
+    sizeofLabel_(static_cast<unsigned char>(sizeof(label))),
+    sizeofScalar_(static_cast<unsigned char>(sizeof(scalar))),
+
+    db_(registry)
 {
     if (objectRegistry::debug)
     {
@@ -334,14 +336,15 @@ Foam::IOobject::IOobject
     note_(),
     instance_(instance),
     local_(local),
-    db_(registry),
     rOpt_(ro),
     wOpt_(wo),
     registerObject_(registerObject),
     globalObject_(globalObject),
     objState_(GOOD),
-    labelByteSize_(sizeof(label)),
-    scalarByteSize_(sizeof(scalar))
+    sizeofLabel_(static_cast<unsigned char>(sizeof(label))),
+    sizeofScalar_(static_cast<unsigned char>(sizeof(scalar))),
+
+    db_(registry)
 {
     if (objectRegistry::debug)
     {
@@ -368,14 +371,15 @@ Foam::IOobject::IOobject
     note_(),
     instance_(),
     local_(),
-    db_(registry),
     rOpt_(ro),
     wOpt_(wo),
     registerObject_(registerObject),
     globalObject_(globalObject),
     objState_(GOOD),
-    labelByteSize_(sizeof(label)),
-    scalarByteSize_(sizeof(scalar))
+    sizeofLabel_(static_cast<unsigned char>(sizeof(label))),
+    sizeofScalar_(static_cast<unsigned char>(sizeof(scalar))),
+
+    db_(registry)
 {
     if (!fileNameComponents(path, instance_, local_, name_))
     {
@@ -405,14 +409,15 @@ Foam::IOobject::IOobject
     note_(io.note_),
     instance_(io.instance_),
     local_(io.local_),
-    db_(registry),
     rOpt_(io.rOpt_),
     wOpt_(io.wOpt_),
     registerObject_(io.registerObject_),
     globalObject_(io.globalObject_),
     objState_(io.objState_),
-    labelByteSize_(io.labelByteSize_),
-    scalarByteSize_(io.scalarByteSize_)
+    sizeofLabel_(io.sizeofLabel_),
+    sizeofScalar_(io.sizeofScalar_),
+
+    db_(registry)
 {}
 
 
@@ -427,14 +432,15 @@ Foam::IOobject::IOobject
     note_(io.note_),
     instance_(io.instance_),
     local_(io.local_),
-    db_(io.db_),
     rOpt_(io.rOpt_),
     wOpt_(io.wOpt_),
     registerObject_(io.registerObject_),
     globalObject_(io.globalObject_),
     objState_(io.objState_),
-    labelByteSize_(io.labelByteSize_),
-    scalarByteSize_(io.scalarByteSize_)
+    sizeofLabel_(io.sizeofLabel_),
+    sizeofScalar_(io.sizeofScalar_),
+
+    db_(io.db_)
 {}
 
 
@@ -566,8 +572,8 @@ void Foam::IOobject::operator=(const IOobject& io)
     wOpt_ = io.wOpt_;
     globalObject_ = io.globalObject_;
     objState_ = io.objState_;
-    labelByteSize_ = io.labelByteSize_;
-    scalarByteSize_ = io.scalarByteSize_;
+    sizeofLabel_ = io.sizeofLabel_;
+    sizeofScalar_ = io.sizeofScalar_;
 }
 
 
diff --git a/src/OpenFOAM/db/IOobject/IOobject.H b/src/OpenFOAM/db/IOobject/IOobject.H
index e8f35947f7..409c503690 100644
--- a/src/OpenFOAM/db/IOobject/IOobject.H
+++ b/src/OpenFOAM/db/IOobject/IOobject.H
@@ -163,9 +163,6 @@ private:
         //- Local path component
         fileName local_;
 
-        //- Reference to the objectRegistry
-        const objectRegistry& db_;
-
         //- Read option
         readOption rOpt_;
 
@@ -181,11 +178,14 @@ private:
         //- IOobject state
         objectState objState_;
 
-        //- The label byte-size (could also be stored as byte)
-        unsigned short labelByteSize_;
+        //- The sizeof (label) in bytes, possibly read from the header
+        unsigned char sizeofLabel_;
 
-        //- The scalar byte-size (could also be stored as byte)
-        unsigned short scalarByteSize_;
+        //- The sizeof (scalar) in bytes, possibly read from the header
+        unsigned char sizeofScalar_;
+
+        //- Reference to the objectRegistry
+        const objectRegistry& db_;
 
 
 protected:
@@ -294,7 +294,8 @@ public:
             const objectRegistry& registry,
             readOption r=NO_READ,
             writeOption w=NO_WRITE,
-            bool registerObject=true
+            bool registerObject = true,
+            bool globalObject = false
         );
 
         //- Construct from name, instance, local, registry, io options
@@ -306,7 +307,7 @@ public:
             const objectRegistry& registry,
             readOption r=NO_READ,
             writeOption w=NO_WRITE,
-            bool registerObject=true,
+            bool registerObject = true,
             bool globalObject = false
         );
 
@@ -368,7 +369,7 @@ public:
         //- Return the local objectRegistry
         const objectRegistry& db() const;
 
-        //- Return time
+        //- Return Time associated with the objectRegistry
         const Time& time() const;
 
         //- Return name
@@ -404,11 +405,11 @@ public:
         //- Is object same for all processors?
         inline bool& globalObject();
 
-        //- The label byte-size, possibly read from the header
-        inline unsigned labelByteSize() const;
+        //- The sizeof (label) in bytes, possibly read from the header
+        inline unsigned labelByteSize() const noexcept;
 
-        //- The scalar byte-size, possibly read from the header
-        inline unsigned scalarByteSize() const;
+        //- The sizeof (scalar) in bytes, possibly read from the header
+        inline unsigned scalarByteSize() const noexcept;
 
 
     // Checks
diff --git a/src/OpenFOAM/db/IOobject/IOobjectI.H b/src/OpenFOAM/db/IOobject/IOobjectI.H
index 2c4f7a84f2..345ca59dd6 100644
--- a/src/OpenFOAM/db/IOobject/IOobjectI.H
+++ b/src/OpenFOAM/db/IOobject/IOobjectI.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -133,15 +133,15 @@ inline bool& Foam::IOobject::globalObject()
 }
 
 
-inline unsigned Foam::IOobject::labelByteSize() const
+inline unsigned Foam::IOobject::labelByteSize() const noexcept
 {
-    return labelByteSize_;
+    return static_cast<unsigned>(sizeofLabel_);
 }
 
 
-inline unsigned Foam::IOobject::scalarByteSize() const
+inline unsigned Foam::IOobject::scalarByteSize() const noexcept
 {
-    return scalarByteSize_;
+    return static_cast<unsigned>(sizeofScalar_);
 }
 
 
diff --git a/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C b/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
index 7726a6d76a..ed0ea688a4 100644
--- a/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
+++ b/src/OpenFOAM/db/IOobject/IOobjectReadHeader.C
@@ -84,22 +84,22 @@ bool Foam::IOobject::readHeader(Istream& is)
         // The note entry is optional
         headerDict.readIfPresent("note", note_);
 
-        labelByteSize_ = sizeof(label);
-        scalarByteSize_ = sizeof(scalar);
+        sizeofLabel_ = sizeof(label);
+        sizeofScalar_ = sizeof(scalar);
 
         // The arch information is optional
         string arch;
         if (headerDict.readIfPresent("arch", arch))
         {
             unsigned val = foamVersion::labelByteSize(arch);
-            if (val) labelByteSize_ = val;
+            if (val) sizeofLabel_ = static_cast<unsigned char>(val);
 
             val = foamVersion::scalarByteSize(arch);
-            if (val) scalarByteSize_ = val;
+            if (val) sizeofScalar_ = static_cast<unsigned char>(val);
         }
 
-        is.setLabelByteSize(labelByteSize_);
-        is.setScalarByteSize(scalarByteSize_);
+        is.setLabelByteSize(sizeofLabel_);
+        is.setScalarByteSize(sizeofScalar_);
     }
     else
     {
diff --git a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
index b4388efb1c..89affe61e0 100644
--- a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
+++ b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.C
@@ -186,8 +186,7 @@ bool Foam::decomposedBlockData::readMasterHeader(IOobject& io, Istream& is)
 void Foam::decomposedBlockData::writeHeader
 (
     Ostream& os,
-    const IOstream::versionNumber version,
-    const IOstream::streamFormat format,
+    IOstreamOption streamOpt,
     const word& objectType,
     const string& note,
     const fileName& location,
@@ -197,8 +196,8 @@ void Foam::decomposedBlockData::writeHeader
     IOobject::writeBanner(os)
         << "FoamFile" << nl
         << '{' << nl
-        << "    version     " << version << ';' << nl
-        << "    format      " << format << ';' << nl
+        << "    version     " << streamOpt.version() << ';' << nl
+        << "    format      " << streamOpt.format() << ';' << nl
         << "    arch        " << foamVersion::buildArch << ';' << nl;
 
     if (Pstream::parRun())
@@ -274,8 +273,8 @@ Foam::autoPtr<Foam::ISstream> Foam::decomposedBlockData::readBlock
         List<char> data(is);
         is.fatalCheck("read(Istream&) : reading entry");
 
-        IOstream::versionNumber ver(IOstream::currentVersion);
-        IOstream::streamFormat fmt;
+        IOstreamOption::versionNumber ver(IOstreamOption::currentVersion);
+        IOstreamOption::streamFormat fmt;
         unsigned labelByteSize;
         unsigned scalarByteSize;
         {
@@ -566,24 +565,24 @@ Foam::autoPtr<Foam::ISstream> Foam::decomposedBlockData::readBlocks
     //- Set stream properties from realIsPtr on master
 
     // Scatter master header info
-    string versionString;
-    label formatValue;
+    int verValue;
+    int fmtValue;
     unsigned labelByteSize;
     unsigned scalarByteSize;
     if (UPstream::master(comm))
     {
-        versionString = realIsPtr().version().str();
-        formatValue = static_cast<label>(realIsPtr().format());
+        verValue = realIsPtr().version().canonical();
+        fmtValue = static_cast<int>(realIsPtr().format());
         labelByteSize = realIsPtr().labelByteSize();
         scalarByteSize = realIsPtr().scalarByteSize();
     }
-    Pstream::scatter(versionString); //,  Pstream::msgType(), comm);
-    Pstream::scatter(formatValue); //,  Pstream::msgType(), comm);
+    Pstream::scatter(verValue); //,  Pstream::msgType(), comm);
+    Pstream::scatter(fmtValue); //,  Pstream::msgType(), comm);
     Pstream::scatter(labelByteSize); //,  Pstream::msgType(), comm);
     Pstream::scatter(scalarByteSize); //,  Pstream::msgType(), comm);
 
-    realIsPtr().version(IOstream::versionNumber(versionString));
-    realIsPtr().format(IOstream::streamFormat(formatValue));
+    realIsPtr().version(IOstreamOption::versionNumber::canonical(verValue));
+    realIsPtr().format(IOstreamOption::streamFormat(fmtValue));
     realIsPtr().setLabelByteSize(labelByteSize);
     realIsPtr().setScalarByteSize(scalarByteSize);
 
@@ -971,20 +970,27 @@ bool Foam::decomposedBlockData::writeData(Ostream& os) const
     const List<char>& data = *this;
 
     IOobject io(*this);
+    IOstreamOption streamOpt(os);
+
+    int verValue;
+    int fmtValue;
 
     // Re-read my own data to find out the header information
     if (Pstream::master(comm_))
     {
         UIListStream headerStream(data);
         io.readHeader(headerStream);
+
+        verValue = headerStream.version().canonical();
+        fmtValue = static_cast<int>(headerStream.format());
     }
 
     // Scatter header information
+    Pstream::scatter(verValue, Pstream::msgType(), comm_);
+    Pstream::scatter(fmtValue, Pstream::msgType(), comm_);
 
-    string versionString(os.version().str());
-    label formatValue(os.format());
-    Pstream::scatter(versionString, Pstream::msgType(), comm_);
-    Pstream::scatter(formatValue, Pstream::msgType(), comm_);
+    streamOpt.version(IOstreamOption::versionNumber::canonical(verValue));
+    streamOpt.format(IOstreamOption::streamFormat(fmtValue));
 
     //word masterName(name());
     //Pstream::scatter(masterName, Pstream::msgType(), comm_);
@@ -999,11 +1005,10 @@ bool Foam::decomposedBlockData::writeData(Ostream& os) const
 
     if (!Pstream::master(comm_))
     {
-        writeHeader
+        decomposedBlockData::writeHeader
         (
             os,
-            IOstreamOption::versionNumber(versionString),
-            IOstreamOption::streamFormat(formatValue),
+            streamOpt,
             io.headerClassName(),
             io.note(),
             masterLocation,
@@ -1074,7 +1079,7 @@ Foam::label Foam::decomposedBlockData::numBlocks(const fileName& fName)
     label nBlocks = 0;
 
     IFstream is(fName);
-    is.fatalCheck("decomposedBlockData::numBlocks(const fileName&)");
+    is.fatalCheck(FUNCTION_NAME);
 
     if (!is.good())
     {
diff --git a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.H b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.H
index 8e790bbc6b..e56059b1a2 100644
--- a/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.H
+++ b/src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockData.H
@@ -67,7 +67,7 @@ protected:
         const label comm_;
 
 
-    // Protected member functions
+    // Protected Member Functions
 
         //- Helper: determine number of processors whose recvSizes fits
         //  ito maxBufferSize
@@ -154,8 +154,7 @@ public:
         static void writeHeader
         (
             Ostream& os,
-            const IOstream::versionNumber version,
-            const IOstream::streamFormat format,
+            IOstreamOption streamOpt,
             const word& objectType,
             const string& note,
             const fileName& location,
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
index 59e20b3530..6e2916411b 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.C
@@ -48,7 +48,7 @@ Foam::IFstream::IFstream
     Foam::ifstreamPointer(pathname),
     ISstream(*(ifstreamPointer::get()), pathname, streamOpt)
 {
-    IOstream::compression(ifstreamPointer::whichCompression());
+    IOstreamOption::compression(ifstreamPointer::whichCompression());
 
     setClosed();
 
@@ -73,7 +73,7 @@ Foam::IFstream::IFstream
                 << "Cannot open empty file name"
                 << Foam::endl;
         }
-        else if (IOstreamOption::COMPRESSED == IOstream::compression())
+        else if (IOstreamOption::COMPRESSED == IOstreamOption::compression())
         {
             InfoInFunction
                 << "Decompressing " << (this->name() + ".gz") << Foam::endl;
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
index 1361725ec2..d28d09d030 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/IFstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -76,7 +76,7 @@ public:
         (
             const fileName& pathname,
             IOstreamOption::streamFormat fmt,
-            IOstreamOption::versionNumber ver = currentVersion
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         )
         :
             IFstream(pathname, IOstreamOption(fmt, ver))
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
index a9a7629d1a..53b9689b45 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/OFstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -81,12 +81,12 @@ public:
         (
             const fileName& pathname,
             IOstreamOption::streamFormat fmt,
-            IOstreamOption::versionNumber ver = currentVersion,
-            IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
             const bool append = false
         )
         :
-            OFstream(pathname, IOstreamOption(fmt, comp, ver), append)
+            OFstream(pathname, IOstreamOption(fmt, ver, cmp), append)
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
index d9a9e7a9d2..f6608a5b7c 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -54,9 +54,7 @@ void Foam::masterOFstream::checkWrite
     OFstream os
     (
         fName,
-        IOstream::BINARY,   //format(),
-        version(),
-        compression_,
+        IOstreamOption(IOstreamOption::BINARY, version(), compression_),
         append_
     );
     if (!os.good())
@@ -189,7 +187,7 @@ Foam::masterOFstream::masterOFstream
     const bool valid
 )
 :
-    OStringStream(streamOpt.format(), streamOpt.version()),
+    OStringStream(streamOpt),
     pathName_(pathName),
     compression_(streamOpt.compression()),
     append_(append),
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
index cfe0b868d7..85be1c4715 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -57,7 +57,7 @@ class masterOFstream
 
         const fileName pathName_;
 
-        const IOstream::compressionType compression_;
+        const IOstreamOption::compressionType compression_;
 
         const bool append_;
 
@@ -99,9 +99,9 @@ public:
         masterOFstream
         (
             const fileName& pathname,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
             const bool append = false,
             const bool valid = true
         )
@@ -109,7 +109,7 @@ public:
             masterOFstream
             (
                 pathname,
-                IOstreamOption(fmt, comp, ver),
+                IOstreamOption(fmt, ver, cmp),
                 append,
                 valid
             )
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.H b/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.H
index 796cdf6d7c..1ae6996c4a 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.H
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/IOstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -64,6 +64,10 @@ using std::cin;
 using std::cout;
 using std::cerr;
 
+// Additional constructors and methods (as per v2012 and earlier)
+#define Foam_IOstream_extras
+// COMPAT_OPENFOAM_ORG
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 namespace Foam
@@ -84,8 +88,8 @@ public:
         //- Enumeration for stream open/closed state
         enum streamAccess : char
         {
-            CLOSED = 0,         //!< stream not open
-            OPENED              //!< stream is open
+            CLOSED = 0,         //!< The stream is not open
+            OPENED              //!< The stream is open
         };
 
 
@@ -102,15 +106,17 @@ protected:
         //- Name for any generic stream - normally treat as readonly
         static fileName staticName_;
 
+        //- Mirror of internal stream io state
+        std::ios_base::iostate ioState_;
+
+        //- The stream open/closed state
         streamAccess openClosed_;
 
-        ios_base::iostate ioState_;
+        //- The sizeof (label), possibly read from the header
+        unsigned char sizeofLabel_;
 
-        //- The label byte-size (could also be stored as byte)
-        unsigned short labelByteSize_;
-
-        //- The scalar byte-size (could also be stored as byte)
-        unsigned short scalarByteSize_;
+        //- The sizeof (scalar), possibly read from the header
+        unsigned char sizeofScalar_;
 
         //- The file line
         label lineNumber_;
@@ -121,27 +127,27 @@ protected:
     // Access
 
         //- Set stream opened
-        void setOpened()
+        void setOpened() noexcept
         {
             openClosed_ = OPENED;
         }
 
         //- Set stream closed
-        void setClosed()
+        void setClosed() noexcept
         {
             openClosed_ = CLOSED;
         }
 
         //- Set stream state
-        void setState(ios_base::iostate state)
+        void setState(std::ios_base::iostate state) noexcept
         {
             ioState_ = state;
         }
 
-        //- Set stream to be good
-        void setGood()
+        //- Set stream state to be good
+        void setGood() noexcept
         {
-            ioState_ = ios_base::iostate(0);
+            ioState_ = std::ios_base::iostate(0);
         }
 
 
@@ -163,10 +169,10 @@ public:
         explicit IOstream(IOstreamOption streamOpt = IOstreamOption())
         :
             IOstreamOption(streamOpt),
+            ioState_(std::ios_base::iostate(0)),
             openClosed_(CLOSED),
-            ioState_(ios_base::iostate(0)),
-            labelByteSize_(sizeof(label)),
-            scalarByteSize_(sizeof(scalar)),
+            sizeofLabel_(static_cast<unsigned char>(sizeof(label))),
+            sizeofScalar_(static_cast<unsigned char>(sizeof(scalar))),
             lineNumber_(0)
         {
             setBad();
@@ -175,12 +181,12 @@ public:
         //- Construct with format, version (compression)
         IOstream
         (
-            streamFormat fmt,
-            versionNumber ver,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            IOstream(IOstreamOption(fmt, comp, ver))
+            IOstream(IOstreamOption(fmt, ver, cmp))
         {}
 
 
@@ -209,50 +215,50 @@ public:
         //  Generate a FatalIOError when an error has occurred.
         bool fatalCheck(const char* operation) const;
 
-        //- Return true if stream has been opened
-        bool opened() const
+        //- True if stream has been opened
+        bool opened() const noexcept
         {
             return openClosed_ == OPENED;
         }
 
-        //- Return true if stream is closed
-        bool closed() const
+        //- True if stream is closed
+        bool closed() const noexcept
         {
             return openClosed_ == CLOSED;
         }
 
-        //- Return true if next operation might succeed
-        bool good() const
+        //- True if next operation might succeed
+        bool good() const noexcept
         {
             return ioState_ == 0;
         }
 
-        //- Return true if end of input seen
-        bool eof() const
+        //- True if end of input seen
+        bool eof() const noexcept
         {
-            return ioState_ & ios_base::eofbit;
+            return ioState_ & std::ios_base::eofbit;
         }
 
-        //- Return true if next operation will fail
-        bool fail() const
+        //- True if next operation will fail
+        bool fail() const noexcept
         {
-            return ioState_ & (ios_base::badbit | ios_base::failbit);
+            return ioState_ & (std::ios_base::badbit | std::ios_base::failbit);
         }
 
-        //- Return true if stream is corrupted
-        bool bad() const
+        //- True if stream is corrupted
+        bool bad() const noexcept
         {
-            return ioState_ & ios_base::badbit;
+            return ioState_ & std::ios_base::badbit;
         }
 
         //- Return true if the stream has not failed
-        explicit operator bool() const
+        explicit operator bool() const noexcept
         {
             return !fail();
         }
 
         //- Return true if the stream has failed
-        bool operator!() const
+        bool operator!() const noexcept
         {
             return fail();
         }
@@ -260,28 +266,28 @@ public:
 
     // Element sizes (precision)
 
-        //- The label byte-size associated with the stream
-        unsigned labelByteSize() const
+        //- The sizeof (label) in bytes associated with the stream
+        unsigned labelByteSize() const noexcept
         {
-            return labelByteSize_;
+            return static_cast<unsigned>(sizeofLabel_);
         }
 
-        //- The scalar byte-size associated with the stream
-        unsigned scalarByteSize() const
+        //- The sizeof (scalar) in bytes associated with the stream
+        unsigned scalarByteSize() const noexcept
         {
-            return scalarByteSize_;
+            return static_cast<unsigned>(sizeofScalar_);
         }
 
-        //- Set the label byte-size associated with the stream
-        void setLabelByteSize(unsigned nbytes)
+        //- Set the sizeof (label) in bytes associated with the stream
+        void setLabelByteSize(unsigned nbytes) noexcept
         {
-            labelByteSize_ = nbytes;
+            sizeofLabel_ = static_cast<unsigned char>(nbytes);
         }
 
-        //- Set the scalar byte-size associated with the stream
-        void setScalarByteSize(unsigned nbytes)
+        //- Set the sizeof (scalar) in bytes associated with the stream
+        void setScalarByteSize(unsigned nbytes) noexcept
         {
-            scalarByteSize_ = nbytes;
+            sizeofScalar_ = static_cast<unsigned char>(nbytes);
         }
 
 
@@ -289,38 +295,38 @@ public:
         //- is the same as the given type
         template<class T = label>
         typename std::enable_if<std::is_integral<T>::value, bool>::type
-        checkLabelSize() const
+        checkLabelSize() const noexcept
         {
-            return labelByteSize_ == sizeof(T);
+            return sizeofLabel_ == sizeof(T);
         }
 
         //- Check if the scalar byte-size associated with the stream
         //- is the same as the given type
         template<class T = scalar>
         typename std::enable_if<std::is_floating_point<T>::value, bool>::type
-        checkScalarSize() const
+        checkScalarSize() const noexcept
         {
-            return scalarByteSize_ == sizeof(T);
+            return sizeofScalar_ == sizeof(T);
         }
 
 
     // Stream State Functions
 
         //- Const access to the current stream line number
-        label lineNumber() const
+        label lineNumber() const noexcept
         {
             return lineNumber_;
         }
 
         //- Non-const access to the current stream line number
-        label& lineNumber()
+        label& lineNumber() noexcept
         {
             return lineNumber_;
         }
 
         //- Set the stream line number
         //  \return the previous value
-        label lineNumber(const label num)
+        label lineNumber(const label num) noexcept
         {
             const label old(lineNumber_);
             lineNumber_ = num;
@@ -331,36 +337,36 @@ public:
         virtual ios_base::fmtflags flags() const = 0;
 
         //- Return the default precision
-        static unsigned int defaultPrecision()
+        static unsigned int defaultPrecision() noexcept
         {
             return precision_;
         }
 
         //- Reset the default precision
         //  \return the previous value
-        static unsigned int defaultPrecision(unsigned int prec)
+        static unsigned int defaultPrecision(unsigned int prec) noexcept
         {
             unsigned int old(precision_);
             precision_ = prec;
             return old;
         }
 
-        //- Set stream to have reached eof
-        void setEof()
+        //- Set stream state as reached 'eof'
+        void setEof() noexcept
         {
-            ioState_ |= ios_base::eofbit;
+            ioState_ |= std::ios_base::eofbit;
         }
 
-        //- Set stream to have failed
-        void setFail()
+        //- Set stream state as 'failed'
+        void setFail() noexcept
         {
-            ioState_ |= ios_base::failbit;
+            ioState_ |= std::ios_base::failbit;
         }
 
-        //- Set stream to be bad
+        //- Set stream state to be 'bad'
         void setBad()
         {
-            ioState_ |= ios_base::badbit;
+            ioState_ |= std::ios_base::badbit;
         }
 
         //- Set flags of stream
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
index 84b7df0036..b1ae05ac4f 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/IOstreamOption.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -123,6 +123,30 @@ public:
 
         // Member Functions
 
+            //- A string representation as major.minor
+            std::string str() const
+            {
+                return
+                (
+                    std::to_string(int(number_ / 10)) // major
+                  + '.'
+                  + std::to_string(int(number_ % 10)) // minor
+                );
+            }
+
+            //- From version to canonical integer value
+            int canonical() const noexcept
+            {
+                return number_;
+            }
+
+            //- From canonical integer value to version
+            static versionNumber canonical(int verNum) noexcept
+            {
+                // Split into major/minor
+                return versionNumber(int(verNum / 10), int(verNum % 10));
+            }
+
             //- Compare differences in the versions
             //  Negative when 'this' is less than other.
             //  Positive when 'this' is greater than other.
@@ -130,33 +154,6 @@ public:
             {
                 return number_ - other.number_;
             }
-
-            //- The canonical major/minor pair as an integer value.
-            int canonical() noexcept
-            {
-                return number_;
-            }
-
-            //- Return the major version number.
-            int getMajor() const noexcept
-            {
-                return int(number_ / 10);
-            }
-
-            //- Return the minor version number
-            int getMinor() const noexcept
-            {
-                return int(number_ % 10);
-            }
-
-            //- A string representation of major.minor
-            std::string str() const
-            {
-                return
-                    std::to_string(getMajor())
-                  + '.'
-                  + std::to_string(getMinor());
-            }
         };
 
 
@@ -364,6 +361,8 @@ public:
 };
 
 
+// * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
+
 //- Output format type as text string (ascii | binary)
 Ostream& operator<<(Ostream& os, const IOstreamOption::streamFormat& fmt);
 
@@ -371,6 +370,8 @@ Ostream& operator<<(Ostream& os, const IOstreamOption::streamFormat& fmt);
 Ostream& operator<<(Ostream& os, const IOstreamOption::versionNumber& ver);
 
 
+// * * * * * * * * * * * * * * * * Global Operators  * * * * * * * * * * * * //
+
 // Comparison Operators
 
 //- Version number equality
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/Istream.H b/src/OpenFOAM/db/IOstreams/IOstreams/Istream.H
index b01dec6bff..051db3781e 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/Istream.H
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/Istream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -96,12 +96,12 @@ public:
         //- Construct with format, version (compression)
         explicit Istream
         (
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            Istream(IOstreamOption(fmt, comp, ver))
+            Istream(IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/IOstreams/Ostream.H b/src/OpenFOAM/db/IOstreams/IOstreams/Ostream.H
index e27dcc0c6a..6f0b87e627 100644
--- a/src/OpenFOAM/db/IOstreams/IOstreams/Ostream.H
+++ b/src/OpenFOAM/db/IOstreams/IOstreams/Ostream.H
@@ -96,12 +96,12 @@ public:
         //- Construct with format, version (compression)
         explicit Ostream
         (
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            Ostream(IOstreamOption(fmt, comp, ver))
+            Ostream(IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.C b/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.C
index ef0fd33d60..db80b49e8a 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,8 +37,8 @@ Foam::IPstream::IPstream
     const label bufSize,
     const int tag,
     const label comm,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     Pstream(commsType, bufSize),
@@ -50,8 +51,8 @@ Foam::IPstream::IPstream
         tag,                        // tag
         comm,
         false,                      // do not clear buf_ if at end
-        format,
-        version
+        fmt,
+        ver
     ),
     externalBufPosition_(0)
 {}
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.H b/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.H
index dd1b090919..fe42f3c2a2 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/IPstream.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -64,7 +65,7 @@ public:
     // Constructors
 
         //- Construct given process index to read from and optional buffer size,
-        //  read format and IO version
+        //- read format and IO version
         IPstream
         (
             const commsTypes commsType,
@@ -72,10 +73,9 @@ public:
             const label bufSize = 0,
             const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm,
-            streamFormat format=BINARY,
-            versionNumber version=currentVersion
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         );
-
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.C b/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.C
index c27649d77c..ee1322fdc0 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,12 +37,12 @@ Foam::OPstream::OPstream
     const label bufSize,
     const int tag,
     const label comm,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     Pstream(commsType, bufSize),
-    UOPstream(commsType, toProcNo, buf_, tag, comm, true, format, version)
+    UOPstream(commsType, toProcNo, buf_, tag, comm, true, fmt, ver)
 {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.H b/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.H
index 52d297a69a..575cb048ba 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/OPstream.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2013 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -55,13 +56,12 @@ class OPstream
     public Pstream,
     public UOPstream
 {
-
 public:
 
     // Constructors
 
         //- Construct given process index to send to and optional buffer size,
-        //  write format and IO version
+        //- write format and IO version
         OPstream
         (
             const commsTypes commsType,
@@ -69,10 +69,9 @@ public:
             const label bufSize = 0,
             const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm,
-            streamFormat format=BINARY,
-            versionNumber version=currentVersion
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         );
-
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
index cd5cb39a85..117e7f505d 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -39,15 +40,15 @@ Foam::PstreamBuffers::PstreamBuffers
     const UPstream::commsTypes commsType,
     const int tag,
     const label comm,
-    IOstream::streamFormat format,
-    IOstream::versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     commsType_(commsType),
     tag_(tag),
     comm_(comm),
-    format_(format),
-    version_(version),
+    format_(fmt),
+    version_(ver),
     sendBuf_(UPstream::nProcs(comm)),
     recvBuf_(UPstream::nProcs(comm)),
     recvBufPos_(UPstream::nProcs(comm), 0),
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
index df57475824..072ce891da 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/PstreamBuffers.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -99,9 +100,9 @@ class PstreamBuffers
 
         const label comm_;
 
-        const IOstream::streamFormat format_;
+        const IOstreamOption::streamFormat format_;
 
-        const IOstream::versionNumber version_;
+        const IOstreamOption::versionNumber version_;
 
         //- Send buffer
         List<DynamicList<char>> sendBuf_;
@@ -130,8 +131,8 @@ public:
             const UPstream::commsTypes commsType,
             const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm,
-            IOstream::streamFormat format=IOstream::BINARY,
-            IOstream::versionNumber version=IOstream::currentVersion
+            IOstreamOption::streamFormat vmt = IOstreamOption::BINARY,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         );
 
     //- Destructor
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H b/src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H
index 508e3e8eb0..9a6b8e7ae8 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/UIPstream.H
@@ -101,7 +101,7 @@ public:
     // Constructors
 
         //- Construct given process index to read from and optional buffer size,
-        //  read format and IO version
+        //- read format and IO version
         UIPstream
         (
             const commsTypes commsType,
@@ -111,8 +111,8 @@ public:
             const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm,
             const bool clearAtEnd = false,   // destroy externalBuf if at end
-            streamFormat format=BINARY,
-            versionNumber version=currentVersion
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         );
 
         //- Construct given buffers
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C b/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C
index 82f72e866b..f550056ca0 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.C
@@ -126,12 +126,12 @@ Foam::UOPstream::UOPstream
     const int tag,
     const label comm,
     const bool sendAtDestruct,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     UPstream(commsType),
-    Ostream(format, version),
+    Ostream(fmt, ver),
     toProcNo_(toProcNo),
     sendBuf_(sendBuf),
     tag_(tag),
diff --git a/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.H b/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.H
index 590a58b92b..68393e97be 100644
--- a/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.H
+++ b/src/OpenFOAM/db/IOstreams/Pstreams/UOPstream.H
@@ -113,8 +113,8 @@ public:
             const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm,
             const bool sendAtDestruct = true,
-            streamFormat format=BINARY,
-            versionNumber version=currentVersion
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
         );
 
         //- Construct given buffers
diff --git a/src/OpenFOAM/db/IOstreams/Sstreams/ISstream.H b/src/OpenFOAM/db/IOstreams/Sstreams/ISstream.H
index eaa2a92420..60206a4db5 100644
--- a/src/OpenFOAM/db/IOstreams/Sstreams/ISstream.H
+++ b/src/OpenFOAM/db/IOstreams/Sstreams/ISstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2012 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -103,12 +103,12 @@ public:
         (
             std::istream& is,
             const string& streamName,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            ISstream(is, streamName, IOstreamOption(fmt, comp, ver))
+            ISstream(is, streamName, IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Sstreams/OSstream.H b/src/OpenFOAM/db/IOstreams/Sstreams/OSstream.H
index 20793f82cd..1efaeca724 100644
--- a/src/OpenFOAM/db/IOstreams/Sstreams/OSstream.H
+++ b/src/OpenFOAM/db/IOstreams/Sstreams/OSstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2014 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -90,12 +90,12 @@ public:
         (
             std::ostream& os,
             const string& streamName,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            OSstream(os, streamName, IOstreamOption(fmt, comp, ver))
+            OSstream(os, streamName, IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Sstreams/prefixOSstream.H b/src/OpenFOAM/db/IOstreams/Sstreams/prefixOSstream.H
index fea59bc2aa..1cdf23ec0e 100644
--- a/src/OpenFOAM/db/IOstreams/Sstreams/prefixOSstream.H
+++ b/src/OpenFOAM/db/IOstreams/Sstreams/prefixOSstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2014 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -28,7 +28,7 @@ Class
     Foam::prefixOSstream
 
 Description
-    Version of OSstream which prints a prefix on each line.
+    Version of OSstream that prints a prefix on each line.
 
     This is useful for running in parallel as it allows the processor number
     to be automatically prepended to each message line.
@@ -85,12 +85,12 @@ public:
         (
             std::ostream& os,
             const string& streamName,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            prefixOSstream(os, streamName, IOstreamOption(fmt, comp, ver))
+            prefixOSstream(os, streamName, IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/OpenFOAM/db/IOstreams/StringStreams/StringStream.H b/src/OpenFOAM/db/IOstreams/StringStreams/StringStream.H
index 49e23bc9b0..e27e2d7a06 100644
--- a/src/OpenFOAM/db/IOstreams/StringStreams/StringStream.H
+++ b/src/OpenFOAM/db/IOstreams/StringStreams/StringStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -71,10 +71,7 @@ protected:
     // Constructors
 
         //- Default construct
-        StringStreamAllocator()
-        :
-            stream_()
-        {}
+        StringStreamAllocator() = default;
 
         //- Copy construct from string
         StringStreamAllocator(const std::string& s)
@@ -107,7 +104,7 @@ public:
                         Class IStringStream Declaration
 \*---------------------------------------------------------------------------*/
 
-//- Input from string buffer, using a ISstream
+//- Input from string buffer, using a ISstream. Always UNCOMPRESSED.
 class IStringStream
 :
     public Detail::StringStreamAllocator<std::istringstream>,
@@ -119,41 +116,36 @@ public:
 
     // Constructors
 
-        //- Default construct
+        //- Default construct or with specified stream option
         explicit IStringStream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            ISstream(stream_, "input", format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
         //- Construct from std::string
         explicit IStringStream
         (
             const std::string& s,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(s),
-            ISstream(stream_, name, format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
         //- Construct from char*
         explicit IStringStream
         (
             const char* s,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(s),
-            ISstream(stream_, name, format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
         //- Copy construct, copies content and format
@@ -185,6 +177,44 @@ public:
         {
             return const_cast<IStringStream&>(*this);
         }
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Default construct
+        explicit IStringStream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IStringStream(IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct from std::string
+        IStringStream
+        (
+            const std::string& s,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IStringStream(s, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct from char*
+        IStringStream
+        (
+            const char* s,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IStringStream(s, IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
@@ -192,7 +222,7 @@ public:
                         Class OStringStream Declaration
 \*---------------------------------------------------------------------------*/
 
-//- Output to string buffer, using a OSstream
+//- Output to string buffer, using a OSstream. Always UNCOMPRESSED.
 class OStringStream
 :
     public Detail::StringStreamAllocator<std::ostringstream>,
@@ -204,15 +234,14 @@ public:
 
     // Constructors
 
-        //- Default construct
+        //- Default construct or with specified stream option
         explicit OStringStream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
         //- Copy construct, copies content and format
@@ -241,6 +270,22 @@ public:
 
         //- Print stream description to Ostream
         virtual void print(Ostream& os) const;
+
+
+    // Older style, without stream option (including 2012 release)
+    #ifdef Foam_IOstream_extras
+
+        //- Default construct
+        explicit OStringStream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OStringStream(IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C b/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C
index 4736a1eb46..41876f5e2a 100644
--- a/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C
+++ b/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C
@@ -55,10 +55,10 @@ Foam::label Foam::ITstream::parseStream(ISstream& is, tokenList& tokens)
 Foam::tokenList Foam::ITstream::parse
 (
     const UList<char>& input,
-    streamFormat format
+    IOstreamOption streamOpt
 )
 {
-    UIListStream is(input, format, IOstream::currentVersion);
+    UIListStream is(input, streamOpt);
 
     tokenList tokens;
     parseStream(is, tokens);
@@ -69,16 +69,10 @@ Foam::tokenList Foam::ITstream::parse
 Foam::tokenList Foam::ITstream::parse
 (
     const std::string& input,
-    streamFormat format
+    IOstreamOption streamOpt
 )
 {
-    UIListStream is
-    (
-        input.data(),
-        input.size(),
-        format,
-        IOstream::currentVersion
-    );
+    UIListStream is(input.data(), input.size(), streamOpt);
 
     tokenList tokens;
     parseStream(is, tokens);
@@ -89,10 +83,10 @@ Foam::tokenList Foam::ITstream::parse
 Foam::tokenList Foam::ITstream::parse
 (
     const char* input,
-    streamFormat format
+    IOstreamOption streamOpt
 )
 {
-    UIListStream is(input, strlen(input), format, IOstream::currentVersion);
+    UIListStream is(input, strlen(input), streamOpt);
 
     tokenList tokens;
     parseStream(is, tokens);
@@ -141,16 +135,15 @@ Foam::ITstream::ITstream
 (
     const string& name,
     const UList<char>& input,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption streamOpt
 )
 :
-    Istream(format, version),
+    Istream(streamOpt.format(), streamOpt.version()),
     tokenList(),
     name_(name),
     tokenIndex_(0)
 {
-    UIListStream is(input, format, version);
+    UIListStream is(input, streamOpt);
 
     parseStream(is, static_cast<tokenList&>(*this));
     ITstream::rewind();
@@ -161,16 +154,15 @@ Foam::ITstream::ITstream
 (
     const string& name,
     const std::string& input,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption streamOpt
 )
 :
-    Istream(format, version),
+    Istream(streamOpt.format(), streamOpt.version()),
     tokenList(),
     name_(name),
     tokenIndex_(0)
 {
-    UIListStream is(input.data(), input.size(), format, version);
+    UIListStream is(input.data(), input.size(), streamOpt);
 
     parseStream(is, static_cast<tokenList&>(*this));
     ITstream::rewind();
@@ -181,16 +173,15 @@ Foam::ITstream::ITstream
 (
     const string& name,
     const char* input,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption streamOpt
 )
 :
-    Istream(format, version),
+    Istream(streamOpt.format(), streamOpt.version()),
     tokenList(),
     name_(name),
     tokenIndex_(0)
 {
-    UIListStream is(input, strlen(input), format, version);
+    UIListStream is(input, strlen(input), streamOpt);
 
     parseStream(is, static_cast<tokenList&>(*this));
     ITstream::rewind();
diff --git a/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H b/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H
index 923d7512f3..394e1df428 100644
--- a/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H
+++ b/src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -115,16 +115,15 @@ public:
             setGood();
         }
 
-        //- Construct from components
+        //- Construct from components, copying the tokens
         ITstream
         (
             const string& name,
             const UList<token>& tokens,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            Istream(format, version),
+            Istream(streamOpt.format(), streamOpt.version()),
             tokenList(tokens),
             name_(name),
             tokenIndex_(0)
@@ -138,11 +137,10 @@ public:
         (
             const string& name,
             List<token>&& tokens,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            Istream(format, version),
+            Istream(streamOpt.format(), streamOpt.version()),
             tokenList(std::move(tokens)),
             name_(name),
             tokenIndex_(0)
@@ -157,8 +155,7 @@ public:
         (
             const string& name,
             const UList<char>& input,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
         //- Construct token list by parsing the input string
@@ -167,8 +164,7 @@ public:
         (
             const string& name,
             const std::string& input,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
         //- Construct token list by parsing the input character sequence
@@ -177,8 +173,7 @@ public:
         (
             const string& name,
             const char* input,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
 
@@ -193,7 +188,7 @@ public:
         static tokenList parse
         (
             const UList<char>& input,
-            streamFormat format=ASCII
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
         //- Create token list by parsing the input string until
@@ -201,7 +196,7 @@ public:
         static tokenList parse
         (
             const std::string& input,
-            streamFormat format=ASCII
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
         //- Create token list by parsing the input character sequence until
@@ -209,7 +204,7 @@ public:
         static tokenList parse
         (
             const char* input,
-            streamFormat format=ASCII
+            IOstreamOption streamOpt = IOstreamOption()
         );
 
 
@@ -359,6 +354,109 @@ public:
 
         //- Move assignment of tokens, with rewind()
         void operator=(List<token>&& toks);
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct from components, copying the tokens
+        ITstream
+        (
+            const string& name,
+            const UList<token>& tokens,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            ITstream(name, tokens, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct from components, transferring the tokens
+        ITstream
+        (
+            const string& name,
+            List<token>&& tokens,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            ITstream(name, std::move(tokens), IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct token list by parsing the input character sequence
+        //  Uses UIListStream internally.
+        ITstream
+        (
+            const string& name,
+            const UList<char>& input,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            ITstream(name, input, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct token list by parsing the input string
+        //  Uses UIListStream internally.
+        ITstream
+        (
+            const string& name,
+            const std::string& input,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            ITstream(name, input, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct token list by parsing the input character sequence
+        //  Uses UIListStream internally.
+        ITstream
+        (
+            const string& name,
+            const char* input,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            ITstream(name, input, IOstreamOption(fmt, ver))
+        {}
+
+
+        //- Create token list by parsing the input character sequence until
+        //- no good tokens remain.
+        static tokenList parse
+        (
+            const UList<char>& input,
+            IOstreamOption::streamFormat fmt
+        )
+        {
+            return parse(input, IOstreamOption(fmt));
+        }
+
+        //- Create token list by parsing the input string until
+        //- no good tokens remain.
+        static tokenList parse
+        (
+            const std::string& input,
+            IOstreamOption::streamFormat fmt
+        )
+        {
+            return parse(input, IOstreamOption(fmt));
+        }
+
+        //- Create token list by parsing the input character sequence until
+        //- no good tokens remain.
+        static tokenList parse
+        (
+            const char* input,
+            IOstreamOption::streamFormat fmt
+        )
+        {
+            return parse(input, IOstreamOption(fmt));
+        }
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.C b/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.C
index 159c31ee4e..7dc51413e5 100644
--- a/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.C
+++ b/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -143,7 +143,7 @@ Foam::Ostream& Foam::OTstream::write(const doubleScalar val)
 
 Foam::Ostream& Foam::OTstream::write(const char* data, std::streamsize count)
 {
-    if (format() != BINARY)
+    if (format() != IOstreamOption::BINARY)
     {
         FatalErrorInFunction
             << "stream format not binary"
@@ -173,7 +173,7 @@ Foam::Ostream& Foam::OTstream::writeRaw
 
 bool Foam::OTstream::beginRawWrite(std::streamsize count)
 {
-    if (format() != BINARY)
+    if (format() != IOstreamOption::BINARY)
     {
         FatalErrorInFunction
             << "stream format not binary"
diff --git a/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.H b/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.H
index b7b56ecaf3..de56b330ba 100644
--- a/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.H
+++ b/src/OpenFOAM/db/IOstreams/Tstreams/OTstream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -73,16 +73,6 @@ public:
             setGood();
         }
 
-        //- Construct with format, version
-        explicit OTstream
-        (
-            streamFormat fmt,
-            versionNumber ver = currentVersion
-        )
-        :
-            OTstream(IOstreamOption(fmt, ver))
-        {}
-
         //- Copy construct
         OTstream(const OTstream& os)
         :
@@ -268,6 +258,22 @@ public:
 
         //- Print stream description to Ostream
         void print(Ostream& os) const;
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct empty with format, version
+        explicit OTstream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OTstream(IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/hashes/OSHA1stream.H b/src/OpenFOAM/db/IOstreams/hashes/OSHA1stream.H
index 3336941f46..763745aa25 100644
--- a/src/OpenFOAM/db/IOstreams/hashes/OSHA1stream.H
+++ b/src/OpenFOAM/db/IOstreams/hashes/OSHA1stream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -72,10 +72,8 @@ class osha1stream
 
     public:
 
-        //- Construct null
-        sha1buf()
-        {}
-
+        //- Default construct
+        sha1buf() = default;
 
         //- Full access to the sha1
         inline SHA1& sha1()
@@ -94,7 +92,7 @@ public:
 
     // Constructors
 
-        //- Construct null
+        //- Default construct
         osha1stream()
         :
             std::ostream(&buf_)
@@ -114,7 +112,6 @@ public:
         {
             return buf_.sha1();
         }
-
 };
 
 
@@ -140,11 +137,8 @@ protected:
 
     // Constructors
 
-        //- Construct null
-        OSHA1streamAllocator()
-        :
-            stream_()
-        {}
+        //- Default construct
+        OSHA1streamAllocator() = default;
 
 
 public:
@@ -170,7 +164,6 @@ public:
         {
             return stream_.sha1().clear();
         }
-
 };
 
 } // End namespace Detail
@@ -201,14 +194,13 @@ public:
     // Constructors
 
         //- Construct with an empty digest
-        OSHA1stream
+        explicit OSHA1stream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            OSstream(stream_, "sha1", format, version)
+            OSstream(stream_, "sha1", streamOpt.format(), streamOpt.version())
         {}
 
 
@@ -230,6 +222,22 @@ public:
         {
             sha1().clear();
         }
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct empty
+        explicit OSHA1stream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OSHA1stream(IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/memory/IListStream.H b/src/OpenFOAM/db/IOstreams/memory/IListStream.H
index 260ea509ab..d641da0587 100644
--- a/src/OpenFOAM/db/IOstreams/memory/IListStream.H
+++ b/src/OpenFOAM/db/IOstreams/memory/IListStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,7 +48,6 @@ See Also
 
 namespace Foam
 {
-
 namespace Detail
 {
 
@@ -130,7 +129,7 @@ public:
                          Class IListStream Declaration
 \*---------------------------------------------------------------------------*/
 
-//- An ISstream with internal List storage
+//- An ISstream with internal List storage. Always UNCOMPRESSED.
 class IListStream
 :
     public Detail::IListStreamAllocator,
@@ -145,26 +144,22 @@ public:
         //- Default construct with an empty list
         explicit IListStream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            ISstream(stream_, "input", format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
-
         //- Move construct from List
         explicit IListStream
         (
             ::Foam::List<char>&& buffer,  // Fully qualify (issue #1521)
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(std::move(buffer)),
-            ISstream(stream_, name, format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
 
@@ -173,13 +168,11 @@ public:
         explicit IListStream
         (
             DynamicList<char,SizeMin>&& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(std::move(buffer)),
-            ISstream(stream_, name, format, version)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
 
@@ -215,6 +208,47 @@ public:
         {
             return const_cast<Istream&>(static_cast<const Istream&>(*this));
         }
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct with an empty list
+        explicit IListStream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IListStream(IOstreamOption(fmt, ver))
+        {}
+
+
+        //- Move construct from List
+        IListStream
+        (
+            ::Foam::List<char>&& buffer,  // Fully qualify (issue #1521)
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IListStream(std::move(buffer), IOstreamOption(fmt, ver))
+        {}
+
+
+        //- Move construct from DynamicList
+        template<int SizeMin>
+        explicit IListStream
+        (
+            DynamicList<char,SizeMin>&& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            IListStream(std::move(buffer), IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/memory/OCountStream.H b/src/OpenFOAM/db/IOstreams/memory/OCountStream.H
index 162a9df941..971856d92c 100644
--- a/src/OpenFOAM/db/IOstreams/memory/OCountStream.H
+++ b/src/OpenFOAM/db/IOstreams/memory/OCountStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -260,12 +260,11 @@ public:
         //- Default construct
         explicit OCountStream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            OSstream(stream_, "count", format, version)
+            OSstream(stream_, "count", streamOpt.format(), streamOpt.version())
         {}
 
         //- Copy construct
@@ -287,6 +286,23 @@ public:
 
         //- Print stream description to Ostream
         virtual void print(Ostream& os) const;
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Default construct
+        explicit OCountStream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OCountStream(IOstreamOption(fmt, ver))
+        {}
+
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/memory/OListStream.H b/src/OpenFOAM/db/IOstreams/memory/OListStream.H
index c556e3ebd3..f02b5ef7f1 100644
--- a/src/OpenFOAM/db/IOstreams/memory/OListStream.H
+++ b/src/OpenFOAM/db/IOstreams/memory/OListStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -409,36 +409,33 @@ public:
         //- Default construct (empty output)
         explicit OListStream
         (
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
         //- Construct with initial reserved number of bytes
         explicit OListStream
         (
             size_t nbytes,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(nbytes),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
         //- Move construct from an existing List
         explicit OListStream
         (
             List<char>&& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(std::move(buffer)),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
         //- Move construct from an existing DynamicList
@@ -446,12 +443,11 @@ public:
         explicit OListStream
         (
             DynamicList<char,SizeMin>&& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(std::move(buffer)),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
 
@@ -466,6 +462,56 @@ public:
 
         //- Print stream description to Ostream
         virtual void print(Ostream& os) const;
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Default construct (empty output)
+        explicit OListStream
+        (
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OListStream(IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct with initial reserved number of bytes
+        explicit OListStream
+        (
+            size_t nbytes,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OListStream(nbytes, IOstreamOption(fmt, ver))
+        {}
+
+        //- Move construct from an existing List
+        OListStream
+        (
+            List<char>&& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OListStream(std::move(buffer), IOstreamOption(fmt, ver))
+        {}
+
+        //- Move construct from an existing DynamicList
+        template<int SizeMin>
+        OListStream
+        (
+            DynamicList<char,SizeMin>&& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            OListStream(std::move(buffer), IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/memory/UIListStream.H b/src/OpenFOAM/db/IOstreams/memory/UIListStream.H
index 3a6c6e98aa..9e3c93f5b0 100644
--- a/src/OpenFOAM/db/IOstreams/memory/UIListStream.H
+++ b/src/OpenFOAM/db/IOstreams/memory/UIListStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -216,54 +216,44 @@ public:
         (
             const char* buffer,
             size_t nbytes,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(const_cast<char*>(buffer), nbytes),
-            ISstream(stream_, name, format, version)
-        {}
-
-
-        //- Construct using data area from a FixedList
-        template<unsigned N>
-        explicit UIListStream
-        (
-            const FixedList<char, N>& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
-        )
-        :
-            UIListStream(buffer.cdata(), N, format, version, name)
+            ISstream(stream_, "input", streamOpt.format(), streamOpt.version())
         {}
 
         //- Construct using data area from a List and number of bytes
         UIListStream
         (
             const UList<char>& buffer,
-            label size,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            size_t nbytes,
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            UIListStream(buffer.cdata(), size, format, version, name)
+            UIListStream(buffer.cdata(), nbytes, streamOpt)
         {}
 
-
         //- Construct using data area from a List and its inherent storage size
         //  Uses addressed size, thus no special treatment for a DynamicList
         explicit UIListStream
         (
             const UList<char>& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion,
-            const Foam::string& name="input"
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            UIListStream(buffer.cdata(), buffer.size(), format, version, name)
+            UIListStream(buffer.cdata(), buffer.size(), streamOpt)
+        {}
+
+        //- Construct using data area from a FixedList
+        template<unsigned N>
+        explicit UIListStream
+        (
+            const FixedList<char, N>& buffer,
+            IOstreamOption streamOpt = IOstreamOption()
+        )
+        :
+            UIListStream(buffer.cdata(), N, streamOpt)
         {}
 
 
@@ -294,6 +284,60 @@ public:
         {
             return const_cast<Istream&>(static_cast<const Istream&>(*this));
         }
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct using specified buffer and number of bytes
+        UIListStream
+        (
+            const char* buffer,
+            size_t nbytes,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UIListStream(buffer, nbytes, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a List and number of bytes
+        UIListStream
+        (
+            const UList<char>& buffer,
+            size_t nbytes,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UIListStream(buffer.cdata(), nbytes, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a List and its inherent storage size
+        //  Uses addressed size, thus no special treatment for a DynamicList
+        UIListStream
+        (
+            const UList<char>& buf,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UIListStream(buf.cdata(), buf.size(), IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a FixedList
+        template<unsigned N>
+        UIListStream
+        (
+            const FixedList<char, N>& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UIListStream(buffer.cdata(), N, IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/IOstreams/memory/UOListStream.H b/src/OpenFOAM/db/IOstreams/memory/UOListStream.H
index 34487f2620..3e8c78226a 100644
--- a/src/OpenFOAM/db/IOstreams/memory/UOListStream.H
+++ b/src/OpenFOAM/db/IOstreams/memory/UOListStream.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -190,24 +190,32 @@ public:
         (
             char* buffer,
             size_t nbytes,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
             allocator_type(buffer, nbytes),
-            OSstream(stream_, "output", format, version)
+            OSstream(stream_, "output", streamOpt.format(), streamOpt.version())
         {}
 
         //- Construct using data area from a List and number of bytes
         UOListStream
         (
             UList<char>& buffer,
-            size_t size,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            size_t nbytes,
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            UOListStream(buffer.data(), size, format, version)
+            UOListStream(buffer.data(), nbytes, streamOpt)
+        {}
+
+        //- Construct using data area from a List and its inherent storage size
+        explicit UOListStream
+        (
+            UList<char>& buffer,
+            IOstreamOption streamOpt = IOstreamOption()
+        )
+        :
+            UOListStream(buffer.data(), buffer.size(), streamOpt)
         {}
 
         //- Construct using data area from a FixedList
@@ -215,35 +223,21 @@ public:
         explicit UOListStream
         (
             FixedList<char, N>& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            UOListStream(buffer.data(), N, format, version)
+            UOListStream(buffer.data(), N, streamOpt)
         {}
 
-        //- Construct using data area from a List and its inherent storage size
-        explicit UOListStream
-        (
-            UList<char>& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
-        )
-        :
-            UOListStream(buffer.data(), buffer.size(), format, version)
-        {}
-
-
         //- Construct using data area from a DynamicList and its capacity
         template<int SizeMin>
         explicit UOListStream
         (
             DynamicList<char,SizeMin>& buffer,
-            streamFormat format=ASCII,
-            versionNumber version=currentVersion
+            IOstreamOption streamOpt = IOstreamOption()
         )
         :
-            UOListStream(buffer.data(), buffer.capacity(), format, version)
+            UOListStream(buffer.data(), buffer.capacity(), streamOpt)
         {}
 
 
@@ -258,6 +252,71 @@ public:
 
         //- Print stream description to Ostream
         virtual void print(Ostream& os) const;
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
+        //- Construct using specified buffer and number of bytes
+        UOListStream
+        (
+            char* buffer,
+            size_t nbytes,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UOListStream(buffer, nbytes, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a List and number of bytes
+        UOListStream
+        (
+            UList<char>& buffer,
+            size_t nbytes,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UOListStream(buffer.data(), nbytes, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a List and its inherent storage size
+        UOListStream
+        (
+            UList<char>& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UOListStream(buffer.data(), buffer.size(), IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a FixedList
+        template<unsigned N>
+        UOListStream
+        (
+            FixedList<char, N>& buffer,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UOListStream(buffer.data(), N, IOstreamOption(fmt, ver))
+        {}
+
+        //- Construct using data area from a DynamicList and its capacity
+        template<int SizeMin>
+        UOListStream
+        (
+            DynamicList<char,SizeMin>& buf,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion
+        )
+        :
+            UOListStream(buf.data(), buf.capacity(), IOstreamOption(fmt, ver))
+        {}
+
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/db/Time/TimeIO.C b/src/OpenFOAM/db/Time/TimeIO.C
index 1a57de375c..dfe975357d 100644
--- a/src/OpenFOAM/db/Time/TimeIO.C
+++ b/src/OpenFOAM/db/Time/TimeIO.C
@@ -249,7 +249,7 @@ void Foam::Time::readDict()
 
             for (simpleRegIOobject* obj : objects)
             {
-                OStringStream os(IOstream::ASCII);
+                OStringStream os;
                 os  << dict;
                 IStringStream is(os.str());
                 obj->readData(is);
diff --git a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
index 5b1cd5f8cd..eb1f21d224 100644
--- a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
+++ b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -252,8 +252,7 @@ Foam::primitiveEntry::primitiveEntry
     (
         is.name() + '.' + key,
         tokenList(10),
-        is.format(),
-        is.version()
+        static_cast<IOstreamOption>(is)
     )
 {
     readEntry(dict, is);
diff --git a/src/OpenFOAM/db/regIOobject/regIOobject.H b/src/OpenFOAM/db/regIOobject/regIOobject.H
index d1ed827872..262122f8bf 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobject.H
+++ b/src/OpenFOAM/db/regIOobject/regIOobject.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -78,7 +78,7 @@ protected:
         //- Helper: check readOpt flags and read if necessary
         bool readHeaderOk
         (
-            const IOstream::streamFormat PstreamFormat,
+            const IOstreamOption::streamFormat fmt,
             const word& typeName
         );
 
@@ -358,9 +358,9 @@ public:
         FOAM_DEPRECATED_FOR(2020-02, "writeObject(IOstreamOption, bool)")
         virtual bool writeObject
         (
-            IOstream::streamFormat fmt,
-            IOstream::versionNumber ver,
-            IOstream::compressionType comp,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver,
+            IOstreamOption::compressionType comp,
             const bool valid
         ) const;
 };
diff --git a/src/OpenFOAM/db/regIOobject/regIOobjectRead.C b/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
index 01b67843c4..f987de0634 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
+++ b/src/OpenFOAM/db/regIOobject/regIOobjectRead.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2018 OpenFOAM Foundation
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -37,7 +37,7 @@ License
 
 bool Foam::regIOobject::readHeaderOk
 (
-    const IOstream::streamFormat format,
+    const IOstreamOption::streamFormat fmt,
     const word& typeName
 )
 {
@@ -77,7 +77,7 @@ bool Foam::regIOobject::readHeaderOk
      || isHeaderOk
     )
     {
-        return fileHandler().read(*this, masterOnly, format, typeName);
+        return fileHandler().read(*this, masterOnly, fmt, typeName);
     }
 
     return false;
diff --git a/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C b/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
index c913550406..867aff11cf 100644
--- a/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
+++ b/src/OpenFOAM/db/regIOobject/regIOobjectWrite.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -28,7 +28,6 @@ License
 
 #include "regIOobject.H"
 #include "Time.H"
-#include "OSspecific.H"
 #include "OFstream.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -42,8 +41,7 @@ bool Foam::regIOobject::writeObject
     if (!good())
     {
         SeriousErrorInFunction
-            << "bad object " << name()
-            << endl;
+            << "bad object " << name() << endl;
 
         return false;
     }
@@ -51,8 +49,7 @@ bool Foam::regIOobject::writeObject
     if (instance().empty())
     {
         SeriousErrorInFunction
-            << "instance undefined for object " << name()
-            << endl;
+            << "instance undefined for object " << name() << endl;
 
         return false;
     }
@@ -97,9 +94,6 @@ bool Foam::regIOobject::writeObject
     }
 
 
-    bool osGood = false;
-
-
     // Everyone check or just master
     bool masterOnly =
         isGlobal
@@ -108,36 +102,9 @@ bool Foam::regIOobject::writeObject
          || regIOobject::fileModificationChecking == inotifyMaster
         );
 
-
+    bool osGood = false;
     if (Pstream::master() || !masterOnly)
     {
-        //if (mkDir(path()))
-        //{
-        //    // Try opening an OFstream for object
-        //    OFstream os(objectPath(), streamOpt);
-        //
-        //    // If any of these fail, return (leave error handling to Ostream
-        //    // class)
-        //    if (!os.good())
-        //    {
-        //        return false;
-        //    }
-        //
-        //    if (!writeHeader(os))
-        //    {
-        //        return false;
-        //    }
-        //
-        //    // Write the data to the Ostream
-        //    if (!writeData(os))
-        //    {
-        //        return false;
-        //    }
-        //
-        //    writeEndDivider(os);
-        //
-        //    osGood = os.good();
-        //}
         osGood = fileHandler().writeObject(*this, streamOpt, valid);
     }
     else
@@ -174,9 +141,9 @@ bool Foam::regIOobject::write(const bool valid) const
 
 bool Foam::regIOobject::writeObject
 (
-    IOstream::streamFormat fmt,
-    IOstream::versionNumber ver,
-    IOstream::compressionType cmp,
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver,
+    IOstreamOption::compressionType cmp,
     const bool valid
 ) const
 {
diff --git a/src/OpenFOAM/global/debug/simpleObjectRegistry.C b/src/OpenFOAM/global/debug/simpleObjectRegistry.C
index 1f20f10b29..445b3f0b81 100644
--- a/src/OpenFOAM/global/debug/simpleObjectRegistry.C
+++ b/src/OpenFOAM/global/debug/simpleObjectRegistry.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -57,7 +57,7 @@ void Foam::simpleObjectRegistry::setValues
 
             if (dEntry.isDict())
             {
-                OStringStream os(IOstream::ASCII);
+                OStringStream os;
                 os  << dEntry.dict();
                 IStringStream is(os.str());
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
index 2f146ea2eb..3ecbd4d1ca 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.C
@@ -44,14 +44,12 @@ namespace Foam
 bool Foam::OFstreamCollator::writeFile
 (
     const label comm,
-    const word& typeName,
+    const word& objectType,
     const fileName& fName,
     const string& masterData,
     const labelUList& recvSizes,
     const PtrList<SubList<char>>& slaveData,    // optional slave data
-    IOstream::streamFormat fmt,
-    IOstream::versionNumber ver,
-    IOstream::compressionType cmp,
+    IOstreamOption streamOpt,
     const bool append
 )
 {
@@ -79,17 +77,7 @@ bool Foam::OFstreamCollator::writeFile
     if (UPstream::master(comm))
     {
         Foam::mkDir(fName.path());
-        osPtr.reset
-        (
-            new OFstream
-            (
-                fName,
-                fmt,
-                ver,
-                cmp,
-                append
-            )
-        );
+        osPtr.reset(new OFstream(fName, streamOpt, append));
 
         // We don't have IOobject so cannot use IOobject::writeHeader
         if (!append)
@@ -97,9 +85,8 @@ bool Foam::OFstreamCollator::writeFile
             decomposedBlockData::writeHeader
             (
                 *osPtr,
-                ver,
-                fmt,
-                typeName,
+                streamOpt,
+                objectType,
                 "",          // note
                 fName,       // location
                 fName.name() // object name
@@ -195,7 +182,7 @@ void* Foam::OFstreamCollator::writeAll(void *threadarg)
             PtrList<SubList<char>> slaveData;
             if (ptr->slaveData_.size())
             {
-                slaveData.setSize(ptr->slaveData_.size());
+                slaveData.resize(ptr->slaveData_.size());
                 forAll(slaveData, proci)
                 {
                     if (ptr->slaveData_.set(proci))
@@ -216,14 +203,12 @@ void* Foam::OFstreamCollator::writeAll(void *threadarg)
             bool ok = writeFile
             (
                 ptr->comm_,
-                ptr->typeName_,
+                ptr->objectType_,
                 ptr->pathName_,
                 ptr->data_,
                 ptr->sizes_,
                 slaveData,
-                ptr->format_,
-                ptr->version_,
-                ptr->compression_,
+                ptr->streamOpt_,
                 ptr->append_
             );
             if (!ok)
@@ -354,12 +339,10 @@ Foam::OFstreamCollator::~OFstreamCollator()
 
 bool Foam::OFstreamCollator::write
 (
-    const word& typeName,
+    const word& objectType,
     const fileName& fName,
     const string& data,
-    IOstream::streamFormat fmt,
-    IOstream::versionNumber ver,
-    IOstream::compressionType cmp,
+    IOstreamOption streamOpt,
     const bool append,
     const bool useThread
 )
@@ -393,14 +376,12 @@ bool Foam::OFstreamCollator::write
         return writeFile
         (
             localComm_,
-            typeName,
+            objectType,
             fName,
             data,
             recvSizes,
             dummySlaveData,
-            fmt,
-            ver,
-            cmp,
+            streamOpt,
             append
         );
     }
@@ -429,7 +410,7 @@ bool Foam::OFstreamCollator::write
             new writeData
             (
                 threadComm_,        // Note: comm not actually used anymore
-                typeName,
+                objectType,
                 fName,
                 (
                     Pstream::master(localComm_)
@@ -437,9 +418,7 @@ bool Foam::OFstreamCollator::write
                   : string::null
                 ),
                 recvSizes,
-                fmt,
-                ver,
-                cmp,
+                streamOpt,
                 append
             )
         );
@@ -559,13 +538,11 @@ bool Foam::OFstreamCollator::write
                 new writeData
                 (
                     threadComm_,
-                    typeName,
+                    objectType,
                     fName,
                     data,
                     recvSizes,
-                    fmt,
-                    ver,
-                    cmp,
+                    streamOpt,
                     append
                 )
             );
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
index ee48b60429..636a0309b7 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/OFstreamCollator.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -42,9 +43,6 @@ Description
     collecting is done locally; the thread only does the writing
     (since the data has already been collected)
 
-
-Operation determine
-
 SourceFiles
     OFstreamCollator.C
 
@@ -71,45 +69,39 @@ namespace Foam
 
 class OFstreamCollator
 {
-    // Private class
+    // Private Class
 
         class writeData
         {
         public:
 
             const label comm_;
-            const word typeName_;
+            const word objectType_;
             const fileName pathName_;
             const string data_;
             const labelList sizes_;
             PtrList<List<char>> slaveData_;
-            const IOstream::streamFormat format_;
-            const IOstream::versionNumber version_;
-            const IOstream::compressionType compression_;
+            const IOstreamOption streamOpt_;
             const bool append_;
 
             writeData
             (
                 const label comm,
-                const word& typeName,
+                const word& objectType,
                 const fileName& pathName,
                 const string& data,
                 const labelList& sizes,
-                IOstream::streamFormat format,
-                IOstream::versionNumber version,
-                IOstream::compressionType compression,
+                IOstreamOption streamOpt,
                 const bool append
             )
             :
                 comm_(comm),
-                typeName_(typeName),
+                objectType_(objectType),
                 pathName_(pathName),
                 data_(data),
                 sizes_(sizes),
-                slaveData_(0),
-                format_(format),
-                version_(version),
-                compression_(compression),
+                slaveData_(),
+                streamOpt_(streamOpt),
                 append_(append)
             {}
 
@@ -157,14 +149,12 @@ class OFstreamCollator
         static bool writeFile
         (
             const label comm,
-            const word& typeName,
+            const word& objectType,
             const fileName& fName,
             const string& masterData,
             const labelUList& recvSizes,
             const PtrList<SubList<char>>& slaveData,
-            IOstream::streamFormat fmt,
-            IOstream::versionNumber ver,
-            IOstream::compressionType cmp,
+            IOstreamOption streamOpt,
             const bool append
         );
 
@@ -185,10 +175,10 @@ public:
     // Constructors
 
         //- Construct from buffer size. 0 = do not use thread
-        OFstreamCollator(const off_t maxBufferSize);
+        explicit OFstreamCollator(const off_t maxBufferSize);
 
-        //- Construct from buffer size (0 = do not use thread) and local
-        //  thread
+        //- Construct from buffer size (0 = do not use thread)
+        //- and specified communicator
         OFstreamCollator(const off_t maxBufferSize, const label comm);
 
 
@@ -196,18 +186,17 @@ public:
     virtual ~OFstreamCollator();
 
 
-    // Member functions
+    // Member Functions
 
-        //- Write file with contents. Blocks until writethread has space
-        //  available (total file sizes < maxBufferSize)
+        //- Write file with contents.
+        //  Blocks until writethread has space available
+        //  (total file sizes < maxBufferSize)
         bool write
         (
-            const word& typeName,
+            const word& objectType,
             const fileName&,
             const string& data,
-            IOstream::streamFormat,
-            IOstream::versionNumber,
-            IOstream::compressionType,
+            IOstreamOption streamOpt,
             const bool append,
             const bool useThread = true
         );
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
index a984a57b38..1fd1bd0ecd 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -161,7 +161,7 @@ bool Foam::fileOperations::collatedFileOperation::appendObject
     // Create string from all data to write
     string buf;
     {
-        OStringStream os(streamOpt.format(), streamOpt.version());
+        OStringStream os(streamOpt);
         if (isMaster)
         {
             if (!io.writeHeader(os))
@@ -204,23 +204,15 @@ bool Foam::fileOperations::collatedFileOperation::appendObject
 
     if (isMaster)
     {
-        IOobject::writeBanner(os)
-            << "FoamFile\n{\n"
-            << "    version     " << os.version() << ";\n"
-            << "    format      " << os.format() << ";\n"
-            << "    class       " << decomposedBlockData::typeName
-            << ";\n";
-
-        // This may be useful to have as well
-        if (os.format() == IOstream::BINARY)
-        {
-            os  << "    arch        " << foamVersion::buildArch << ";\n";
-        }
-
-        os  << "    location    " << pathName << ";\n"
-            << "    object      " << pathName.name() << ";\n"
-            << "}" << nl;
-        IOobject::writeDivider(os) << nl;
+        decomposedBlockData::writeHeader
+        (
+            os,
+            static_cast<IOstreamOption>(os),
+            decomposedBlockData::typeName,  // class
+            "",                             // note
+            pathName,                       // location
+            pathName.name()                 // object
+        );
     }
 
     // Write data
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
index 7876080e84..fd421743fe 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/collatedFileOperation.H
@@ -105,7 +105,7 @@ public:
         TypeName("collated");
 
 
-    // Static data
+    // Static Data
 
         //- Max size of thread buffer size. This is the overall size of
         //  all files to be written. Starts blocking if not enough size.
@@ -115,8 +115,8 @@ public:
 
     // Constructors
 
-        //- Construct null
-        collatedFileOperation(bool verbose);
+        //- Default construct
+        explicit collatedFileOperation(bool verbose);
 
         //- Construct from user communicator
         collatedFileOperation
@@ -163,8 +163,8 @@ public:
             //- Actual name of processors dir
             virtual word processorsDir(const fileName&) const;
 
-            //- Set number of processor directories/results. Only used in
-            //  decomposePar
+            //- Set number of processor directories/results.
+            //- Only used in decomposePar
             virtual void setNProcs(const label nProcs);
 };
 
@@ -197,9 +197,7 @@ public:
         //- Needs threading
         virtual bool needsThreading() const
         {
-            return
-                collatedFileOperation::maxThreadFileBufferSize
-              > 0;
+            return (collatedFileOperation::maxThreadFileBufferSize > 0);
         }
 };
 
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
index f1b5dc58c6..5927583cc3 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/hostCollatedFileOperation.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -90,8 +91,8 @@ public:
 
     // Constructors
 
-        //- Construct null
-        hostCollatedFileOperation(const bool verbose);
+        //- Default construct
+        explicit hostCollatedFileOperation(const bool verbose);
 
 
     //- Destructor
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
index e3c7cc20ed..07d1ffc146 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -40,7 +40,7 @@ Foam::threadedCollatedOFstream::threadedCollatedOFstream
     const bool useThread
 )
 :
-    OStringStream(streamOpt.format(), streamOpt.version()),
+    OStringStream(streamOpt),
     writer_(writer),
     pathName_(pathName),
     compression_(streamOpt.compression()),
@@ -57,9 +57,7 @@ Foam::threadedCollatedOFstream::~threadedCollatedOFstream()
         decomposedBlockData::typeName,
         pathName_,
         str(),
-        IOstream::BINARY,
-        version(),
-        compression_,
+        IOstreamOption(IOstream::BINARY, version(), compression_),
         false,  // append=false
         useThread_
     );
diff --git a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
index 87990ec39a..fabc873f5e 100644
--- a/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
+++ b/src/OpenFOAM/global/fileOperations/collatedFileOperation/threadedCollatedOFstream.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -44,6 +45,7 @@ SourceFiles
 namespace Foam
 {
 
+// Forward Declarations
 class OFstreamCollator;
 
 /*---------------------------------------------------------------------------*\
@@ -54,13 +56,14 @@ class threadedCollatedOFstream
 :
     public OStringStream
 {
-    // Private data
+    // Private Data
 
+        //- The backend writer
         OFstreamCollator& writer_;
 
         const fileName pathName_;
 
-        const IOstream::compressionType compression_;
+        const IOstreamOption::compressionType compression_;
 
         const bool useThread_;
 
@@ -78,14 +81,22 @@ public:
             const bool useThread = true
         );
 
+
+    //- Destructor
+    ~threadedCollatedOFstream();
+
+
+    // Additional constructors and methods (as per v2012 and earlier)
+    #ifdef Foam_IOstream_extras
+
         //- Construct and set stream status
         threadedCollatedOFstream
         (
             OFstreamCollator& writer,
             const fileName& pathname,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED,
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED,
             const bool useThread = true
         )
         :
@@ -93,14 +104,12 @@ public:
             (
                 writer,
                 pathname,
-                IOstreamOption(fmt, ver, comp),
+                IOstreamOption(fmt, ver, cmp),
                 useThread
             )
         {}
 
-
-    //- Destructor
-    ~threadedCollatedOFstream();
+    #endif /* Foam_IOstream_extras */
 };
 
 
diff --git a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
index 412c22ef86..ac3ce897a7 100644
--- a/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -437,7 +437,7 @@ public:
             (
                 regIOobject&,
                 const bool masterOnly,
-                const IOstream::streamFormat format,
+                const IOstreamOption::streamFormat format,
                 const word& typeName
             ) const = 0;
 
diff --git a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
index 2dc64cb039..69a078a22e 100644
--- a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017-2018 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -500,7 +500,7 @@ void Foam::fileOperations::masterUncollatedFileOperation::readAndSend
     PstreamBuffers& pBufs
 )
 {
-    IFstream ifs(filePath, IOstream::streamFormat::BINARY);
+    IFstream ifs(filePath, IOstreamOption::BINARY);
 
     if (!ifs.good())
     {
@@ -516,7 +516,7 @@ void Foam::fileOperations::masterUncollatedFileOperation::readAndSend
             << filePath << endl;
     }
 
-    if (ifs.compression() == IOstream::compressionType::COMPRESSED)
+    if (ifs.compression() == IOstreamOption::COMPRESSED)
     {
         // Could use Foam::fileSize, estimate uncompressed size (eg, 2x)
         // and then string reserve followed by string assign...
@@ -2087,7 +2087,7 @@ bool Foam::fileOperations::masterUncollatedFileOperation::read
 (
     regIOobject& io,
     const bool masterOnly,
-    const IOstream::streamFormat format,
+    const IOstreamOption::streamFormat format,
     const word& typeName
 ) const
 {
@@ -2203,7 +2203,7 @@ bool Foam::fileOperations::masterUncollatedFileOperation::writeObject
     setTime(io.time());
 
     autoPtr<OSstream> osPtr(NewOFstream(pathName, streamOpt, valid));
-    OSstream& os = osPtr();
+    OSstream& os = *osPtr;
 
     // If any of these fail, return (leave error handling to Ostream class)
     if (!os.good())
diff --git a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
index 03ccd0fd61..661f07759c 100644
--- a/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -89,7 +89,7 @@ class masterUncollatedFileOperation
 {
 protected:
 
-    // Protected data
+    // Protected Data
 
         //- Any communicator allocated by me
         const label myComm_;
@@ -98,7 +98,7 @@ protected:
         mutable HashPtrTable<instantList> times_;
 
 
-    // Protected classes
+    // Protected Classes
 
         class mkDirOp
         {
@@ -488,8 +488,8 @@ public:
 
     // Constructors
 
-        //- Construct null
-        masterUncollatedFileOperation(bool verbose);
+        //- Default construct
+        explicit masterUncollatedFileOperation(bool verbose);
 
         //- Construct from communicator
         masterUncollatedFileOperation(const label comm, bool verbose);
@@ -679,7 +679,7 @@ public:
             (
                 regIOobject&,
                 const bool masterOnly,
-                const IOstream::streamFormat format,
+                const IOstreamOption::streamFormat format,
                 const word& typeName
             ) const;
 
diff --git a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
index b930c685fe..d54f983e83 100644
--- a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
+++ b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -613,7 +613,7 @@ bool Foam::fileOperations::uncollatedFileOperation::read
 (
     regIOobject& io,
     const bool masterOnly,
-    const IOstream::streamFormat format,
+    const IOstreamOption::streamFormat format,
     const word& typeName
 ) const
 {
diff --git a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
index 3e2ec313e4..fc5d7b1b8d 100644
--- a/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
+++ b/src/OpenFOAM/global/fileOperations/uncollatedFileOperation/uncollatedFileOperation.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -86,7 +86,7 @@ public:
     // Constructors
 
         //- Default construct
-        uncollatedFileOperation(bool verbose);
+        explicit uncollatedFileOperation(bool verbose);
 
 
     //- Destructor
@@ -272,7 +272,7 @@ public:
             (
                 regIOobject&,
                 const bool masterOnly,
-                const IOstream::streamFormat format,
+                const IOstreamOption::streamFormat format,
                 const word& typeName
             ) const;
 
diff --git a/src/OpenFOAM/interpolations/interpolationTable/tableReaders/csv/csvTableReader.C b/src/OpenFOAM/interpolations/interpolationTable/tableReaders/csv/csvTableReader.C
index bc09a69dde..4e2ebaab6d 100644
--- a/src/OpenFOAM/interpolations/interpolationTable/tableReaders/csv/csvTableReader.C
+++ b/src/OpenFOAM/interpolations/interpolationTable/tableReaders/csv/csvTableReader.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2020 OpenCFD Ltd.
+    Copyright (C) 2020-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -225,10 +225,9 @@ void Foam::csvTableReader<Type>::write(Ostream& os) const
     os.writeEntry("refColumn", refColumn_);
 
     // Force writing labelList in ASCII
-    const enum IOstream::streamFormat fmt = os.format();
-    os.format(IOstream::ASCII);
+    const auto oldFmt = os.format(IOstream::ASCII);
     os.writeEntry("componentColumns", componentColumns_);
-    os.format(fmt);
+    os.format(oldFmt);
 
     os.writeEntry("separator", string(separator_));
 }
diff --git a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
index 81bf9400b3..001b19df7b 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C
@@ -1181,7 +1181,7 @@ bool Foam::polyBoundaryMesh::writeObject
     const bool valid
 ) const
 {
-    streamOpt.compression(IOstream::UNCOMPRESSED);
+    streamOpt.compression(IOstreamOption::UNCOMPRESSED);
     return regIOobject::writeObject(streamOpt, valid);
 }
 
diff --git a/src/OpenFOAM/primitives/functions/Function1/CSV/CSV.C b/src/OpenFOAM/primitives/functions/Function1/CSV/CSV.C
index 1aaedfa1d5..03fb6b86c0 100644
--- a/src/OpenFOAM/primitives/functions/Function1/CSV/CSV.C
+++ b/src/OpenFOAM/primitives/functions/Function1/CSV/CSV.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -260,10 +260,9 @@ void Foam::Function1Types::CSV<Type>::writeEntries(Ostream& os) const
     os.writeEntry("refColumn", refColumn_);
 
     // Force writing labelList in ASCII
-    const enum IOstream::streamFormat fmt = os.format();
-    os.format(IOstream::ASCII);
+    const auto oldFmt = os.format(IOstream::ASCII);
     os.writeEntry("componentColumns", componentColumns_);
-    os.format(fmt);
+    os.format(oldFmt);
 
     os.writeEntry("separator", string(separator_));
     os.writeEntry("mergeSeparators", mergeSeparators_);
diff --git a/src/Pstream/dummy/UIPread.C b/src/Pstream/dummy/UIPread.C
index 2817f74ac5..3663e35f59 100644
--- a/src/Pstream/dummy/UIPread.C
+++ b/src/Pstream/dummy/UIPread.C
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
+    Copyright (C) 2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -41,12 +42,12 @@ Foam::UIPstream::UIPstream
     const int tag,
     const label comm,
     const bool clearAtEnd,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     UPstream(commsType),
-    Istream(format, version),
+    Istream(fmt, ver),
     fromProcNo_(fromProcNo),
     externalBuf_(externalBuf),
     externalBufPosition_(externalBufPosition),
@@ -88,8 +89,7 @@ Foam::label Foam::UIPstream::read
 )
 {
     NotImplemented;
-
-     return 0;
+    return 0;
 }
 
 
diff --git a/src/Pstream/mpi/UIPread.C b/src/Pstream/mpi/UIPread.C
index 5fed1729e3..6b04ff48b6 100644
--- a/src/Pstream/mpi/UIPread.C
+++ b/src/Pstream/mpi/UIPread.C
@@ -47,12 +47,12 @@ Foam::UIPstream::UIPstream
     const int tag,
     const label comm,
     const bool clearAtEnd,
-    streamFormat format,
-    versionNumber version
+    IOstreamOption::streamFormat fmt,
+    IOstreamOption::versionNumber ver
 )
 :
     UPstream(commsType),
-    Istream(format, version),
+    Istream(fmt, ver),
     fromProcNo_(fromProcNo),
     externalBuf_(externalBuf),
     externalBufPosition_(externalBufPosition),
diff --git a/src/conversion/ccm/reader/ccmReader.C b/src/conversion/ccm/reader/ccmReader.C
index 4a36f83921..838b5d234f 100644
--- a/src/conversion/ccm/reader/ccmReader.C
+++ b/src/conversion/ccm/reader/ccmReader.C
@@ -579,17 +579,13 @@ bool Foam::ccm::reader::hasSolution()
 void Foam::ccm::reader::writeMesh
 (
     const polyMesh& mesh,
-    IOstream::streamFormat fmt
+    IOstreamOption streamOpt
 ) const
 {
     mesh.removeFiles();
 
     Info<< "Writing polyMesh" << endl;
-    mesh.writeObject
-    (
-        IOstreamOption(fmt),
-        true
-    );
+    mesh.writeObject(streamOpt, true);
     writeAux(mesh);
 }
 
diff --git a/src/conversion/ccm/reader/ccmReader.H b/src/conversion/ccm/reader/ccmReader.H
index f84425911d..283005fd6d 100644
--- a/src/conversion/ccm/reader/ccmReader.H
+++ b/src/conversion/ccm/reader/ccmReader.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -161,7 +161,6 @@ SourceFiles
 #include "ccmInterfaceDefinitions.H"
 #include "ccmSolutionTable.H"
 
-
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 namespace Foam
@@ -395,7 +394,7 @@ private:
             const objectRegistry& registry,
             const word& propertyName,
             const labelList& list,
-            IOstream::streamFormat fmt = IOstream::ASCII
+            IOstreamOption streamOpt
         ) const;
 
         // polyMesh Friend Functions
@@ -493,7 +492,7 @@ public:
         void writeMesh
         (
             const polyMesh& mesh,
-            IOstream::streamFormat fmt = IOstream::BINARY
+            IOstreamOption streamOpt = IOstreamOption(IOstreamOption::BINARY)
         ) const;
 
         //- Write cellTable, boundaryRegion and interface information
diff --git a/src/conversion/ccm/reader/ccmReaderAux.C b/src/conversion/ccm/reader/ccmReaderAux.C
index 8853d2a642..3031b000d6 100644
--- a/src/conversion/ccm/reader/ccmReaderAux.C
+++ b/src/conversion/ccm/reader/ccmReaderAux.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -146,7 +146,7 @@ void Foam::ccm::reader::writeMeshLabelList
     const objectRegistry& registry,
     const word& propertyName,
     const labelList& list,
-    IOstream::streamFormat fmt
+    IOstreamOption streamOpt
 ) const
 {
     // Write constant/polyMesh/propertyName
@@ -171,12 +171,8 @@ void Foam::ccm::reader::writeMeshLabelList
     // NOTE:
     // The cellTableId is an integer and almost always < 1000, thus ASCII
     // will be compacter than binary and makes external scripting easier
-    //
-    ioObj.writeObject
-    (
-        IOstreamOption(fmt),
-        true
-    );
+
+    ioObj.writeObject(streamOpt, true);
 }
 
 
@@ -197,7 +193,7 @@ void Foam::ccm::reader::writeAux
         registry,
         "origCellId",
         origCellId_,
-        IOstream::BINARY
+        IOstreamOption(IOstreamOption::BINARY)
     );
 
     // Write cellTableId as List<label>
@@ -207,7 +203,7 @@ void Foam::ccm::reader::writeAux
         registry,
         "cellTableId",
         cellTableId_,
-        IOstream::ASCII
+        IOstreamOption(IOstreamOption::ASCII)
     );
 }
 
diff --git a/src/conversion/common/reader/meshReader.C b/src/conversion/common/reader/meshReader.C
index 5db5fb6b0d..0c8e96e71f 100644
--- a/src/conversion/common/reader/meshReader.C
+++ b/src/conversion/common/reader/meshReader.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -124,17 +124,13 @@ Foam::autoPtr<Foam::polyMesh> Foam::meshReader::mesh
 void Foam::meshReader::writeMesh
 (
     const polyMesh& mesh,
-    IOstream::streamFormat fmt
+    IOstreamOption streamOpt
 ) const
 {
     mesh.removeFiles();
 
     Info<< "Writing polyMesh" << endl;
-    mesh.writeObject
-    (
-        IOstreamOption(fmt),
-        true
-    );
+    mesh.writeObject(streamOpt, true);
     writeAux(mesh);
 }
 
diff --git a/src/conversion/common/reader/meshReader.H b/src/conversion/common/reader/meshReader.H
index aed1acadf6..d584a02b76 100644
--- a/src/conversion/common/reader/meshReader.H
+++ b/src/conversion/common/reader/meshReader.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -193,7 +193,7 @@ private:
             const objectRegistry& registry,
             const word& propertyName,
             const labelList& list,
-            IOstream::streamFormat fmt = IOstream::ASCII
+            IOstreamOption streamOpt
         ) const;
 
         //- Return list of faces for every cell
@@ -291,7 +291,7 @@ public:
         void writeMesh
         (
             const polyMesh&,
-            IOstream::streamFormat fmt = IOstream::BINARY
+            IOstreamOption streamOpt = IOstreamOption(IOstreamOption::BINARY)
         ) const;
 };
 
diff --git a/src/conversion/common/reader/meshReaderAux.C b/src/conversion/common/reader/meshReaderAux.C
index 0503737b2a..dbe35efb53 100644
--- a/src/conversion/common/reader/meshReaderAux.C
+++ b/src/conversion/common/reader/meshReaderAux.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -109,7 +109,7 @@ void Foam::meshReader::writeMeshLabelList
     const objectRegistry& registry,
     const word& propertyName,
     const labelList& list,
-    IOstream::streamFormat fmt
+    IOstreamOption streamOpt
 ) const
 {
     // write constant/polyMesh/propertyName
@@ -129,14 +129,14 @@ void Foam::meshReader::writeMeshLabelList
     );
 
 
-    ioObj.note() = "persistent data for star-cd <-> foam translation";
+    ioObj.note() = "persistent data for STARCD <-> OPENFOAM translation";
     Info<< "Writing " << ioObj.name() << " to " << ioObj.objectPath() << endl;
 
     // NOTE:
     // the cellTableId is an integer and almost always < 1000, thus ASCII
     // will be compacter than binary and makes external scripting easier
 
-    ioObj.writeObject(IOstreamOption(fmt), true);
+    ioObj.writeObject(streamOpt, true);
 }
 
 
@@ -153,7 +153,7 @@ void Foam::meshReader::writeAux(const objectRegistry& registry) const
         registry,
         "origCellId",
         origCellId_,
-        IOstream::BINARY
+        IOstreamOption(IOstreamOption::BINARY)
     );
 
     // write cellTableId as List<label>
@@ -163,7 +163,7 @@ void Foam::meshReader::writeAux(const objectRegistry& registry) const
         registry,
         "cellTableId",
         cellTableId_,
-        IOstream::ASCII
+        IOstreamOption(IOstreamOption::ASCII)
     );
 }
 
diff --git a/src/conversion/fire/FIREMeshReader.C b/src/conversion/fire/FIREMeshReader.C
index 88e9e26b98..f6285521d0 100644
--- a/src/conversion/fire/FIREMeshReader.C
+++ b/src/conversion/fire/FIREMeshReader.C
@@ -376,7 +376,7 @@ void Foam::fileFormats::FIREMeshReader::addPatches(polyMesh& mesh) const
 
 bool Foam::fileFormats::FIREMeshReader::readGeometry(const scalar scaleFactor)
 {
-    IOstream::streamFormat fmt = IOstream::ASCII;
+    IOstreamOption::streamFormat fmt = IOstream::ASCII;
 
     const word ext(geometryFile_.ext());
 
diff --git a/src/fileFormats/ensight/read/ensightReadFile.C b/src/fileFormats/ensight/read/ensightReadFile.C
index 22c7a2bae8..1697fdea01 100644
--- a/src/fileFormats/ensight/read/ensightReadFile.C
+++ b/src/fileFormats/ensight/read/ensightReadFile.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2019 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -32,10 +32,10 @@ License
 Foam::ensightReadFile::ensightReadFile
 (
     const fileName& pathname,
-    IOstream::streamFormat format
+    IOstreamOption::streamFormat fmt
 )
 :
-    IFstream(pathname, format)
+    IFstream(pathname, fmt)
 {}
 
 
diff --git a/src/fileFormats/ensight/read/ensightReadFile.H b/src/fileFormats/ensight/read/ensightReadFile.H
index d456c3e032..a19e3103a8 100644
--- a/src/fileFormats/ensight/read/ensightReadFile.H
+++ b/src/fileFormats/ensight/read/ensightReadFile.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -65,10 +65,10 @@ public:
     // Constructors
 
         //- Construct from pathname. Default format is binary.
-        ensightReadFile
+        explicit ensightReadFile
         (
             const fileName& pathname,
-            IOstream::streamFormat format=IOstream::BINARY
+            IOstreamOption::streamFormat fmt = IOstreamOption::BINARY
         );
 
 
diff --git a/src/fileFormats/fire/FIRECore.C b/src/fileFormats/fire/FIRECore.C
index d16be2cb48..1fa596f139 100644
--- a/src/fileFormats/fire/FIRECore.C
+++ b/src/fileFormats/fire/FIRECore.C
@@ -204,7 +204,7 @@ void Foam::fileFormats::FIRECore::putFireLabel
     const label value
 )
 {
-    if (os.format() == Foam::IOstream::BINARY)
+    if (os.format() == IOstream::BINARY)
     {
         fireInt_t ivalue(value);
 
diff --git a/src/fileFormats/obj/OBJstream.H b/src/fileFormats/obj/OBJstream.H
index bfba632494..2b319aedf3 100644
--- a/src/fileFormats/obj/OBJstream.H
+++ b/src/fileFormats/obj/OBJstream.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2015 OpenFOAM Foundation
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -90,12 +90,12 @@ public:
         OBJstream
         (
             const fileName& pathname,
-            streamFormat fmt,
-            versionNumber ver = currentVersion,
-            compressionType comp = compressionType::UNCOMPRESSED
+            IOstreamOption::streamFormat fmt,
+            IOstreamOption::versionNumber ver = IOstreamOption::currentVersion,
+            IOstreamOption::compressionType cmp = IOstreamOption::UNCOMPRESSED
         )
         :
-            OBJstream(pathname, IOstreamOption(fmt, ver, comp))
+            OBJstream(pathname, IOstreamOption(fmt, ver, cmp))
         {}
 
 
diff --git a/src/sampling/sampledSurface/readers/ensight/ensightSurfaceReader.H b/src/sampling/sampledSurface/readers/ensight/ensightSurfaceReader.H
index ec120d7923..20eae6f21a 100644
--- a/src/sampling/sampledSurface/readers/ensight/ensightSurfaceReader.H
+++ b/src/sampling/sampledSurface/readers/ensight/ensightSurfaceReader.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -69,7 +69,7 @@ protected:
         };
 
         //- Format flag
-        IOstream::streamFormat streamFormat_;
+        IOstreamOption::streamFormat streamFormat_;
 
         //- Base directory
         fileName baseDir_;
diff --git a/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.C b/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.C
index e002ea79d4..6bc87cd8ae 100644
--- a/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.C
+++ b/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -204,7 +204,7 @@ void Foam::fileFormats::STLsurfaceFormat<Face>::writeAscii
 (
     const fileName& filename,
     const MeshedSurfaceProxy<Face>& surf,
-    IOstream::compressionType comp
+    IOstreamOption::compressionType comp
 )
 {
     OFstream os(filename, IOstreamOption(IOstream::ASCII, comp));
@@ -303,7 +303,7 @@ void Foam::fileFormats::STLsurfaceFormat<Face>::writeAscii
 (
     const fileName& filename,
     const UnsortedMeshedSurface<Face>& surf,
-    IOstream::compressionType comp
+    IOstreamOption::compressionType comp
 )
 {
     const pointField& pointLst = surf.points();
@@ -416,7 +416,7 @@ void Foam::fileFormats::STLsurfaceFormat<Face>::write
     const fileName& filename,
     const MeshedSurfaceProxy<Face>& surf,
     const STLFormat format,
-    IOstream::compressionType comp
+    IOstreamOption::compressionType comp
 )
 {
     if (STLCore::isBinaryName(filename, format))
@@ -461,7 +461,7 @@ void Foam::fileFormats::STLsurfaceFormat<Face>::write
     const fileName& filename,
     const UnsortedMeshedSurface<Face>& surf,
     const STLFormat format,
-    IOstream::compressionType comp
+    IOstreamOption::compressionType comp
 )
 {
     if (STLCore::isBinaryName(filename, format))
diff --git a/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.H b/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.H
index 4167afdb88..b91bb1e849 100644
--- a/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.H
+++ b/src/surfMesh/surfaceFormats/stl/STLsurfaceFormat.H
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2016-2020 OpenCFD Ltd.
+    Copyright (C) 2016-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -108,7 +108,7 @@ public:
         (
             const fileName& filename,
             const MeshedSurfaceProxy<Face>& surf,
-            IOstream::compressionType comp = IOstream::UNCOMPRESSED
+            IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED
         );
 
         //- Write surface mesh components by proxy (as BINARY)
@@ -123,7 +123,7 @@ public:
         (
             const fileName& filename,
             const UnsortedMeshedSurface<Face>& surf,
-            IOstream::compressionType comp = IOstream::UNCOMPRESSED
+            IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED
         );
 
         //- Write UnsortedMeshedSurface (as BINARY) unsorted by zone
@@ -140,7 +140,7 @@ public:
             const fileName& filename,
             const MeshedSurfaceProxy<Face>& surf,
             const STLFormat format,
-            IOstream::compressionType comp = IOstream::UNCOMPRESSED
+            IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED
         );
 
         //- Write UnsortedMeshedSurface
@@ -150,7 +150,7 @@ public:
             const fileName& filename,
             const UnsortedMeshedSurface<Face>& surf,
             const STLFormat format,
-            IOstream::compressionType comp = IOstream::UNCOMPRESSED
+            IOstreamOption::compressionType comp = IOstreamOption::UNCOMPRESSED
         );