The problem with your constant code is that you have now created a scope issue and it's not extensible. This means that if one used it hidden in a package, and additional types are added to the system, the package would fail with the new types until teh package was reprogrammed.

I'm not sure the issue is as trivial as you expect.

An additional fix for my original code uses a non-file stream. That would eliminate the need to open a file. A memory stream should work just as well.

I think you're misunderstanding what I mean. I want a function that returns the integer number value of the byte size of a numerical data type.

Here is the work around that I have devised.

GetTypeSize[datatype_] :=
(
Module[
(*incoming parameters*)
{atype=datatype},
Block[{fp},
fp = OpenWrite["a1234pacximus.bin",BinaryFormat->True];
a = BinaryWrite[fp,1,atype,ByteOrdering->-1];
Close[fp];
];(*end block*)
FileByteCount["a1234pacximus.bin"]
](*end of module*)
)
(*end if GetTypeSize*)

Examples of calling this function would be:

realsz = GetTypeSize["Real32"];
intsz = GetTypeSize["Integer24"];

I thought the language designers may have a function for getting the size of a type already.