Question

I have been learning Visual C++ Win32 programming for some time now.
Why are there the datatypes like DWORD, WCHAR, UINT etc. used instead of, say, unsigned long, char, unsigned int and so on?

I have to remember when to use WCHAR instead of const char *, and it is really annoying me.
Why aren’t the standard datatypes used in the first place? Will it help if I memorize Win32 equivalents and use these for my own variables as well?

Answer 1

Yes, you should use the correct data-type for the arguments for functions, or you are likely to find yourself with trouble.

And the reason that these types are defined the way they are, rather than using int, char and so on is that it removes the “whatever the compiler thinks an int should be sized as” from the interface of the OS. Which is a very good thing, because if you use compiler A, or compiler B, or compiler C, they will all use the same types – only the library interface header file needs to do the right thing defining the types.

By defining types that are not standard types, it’s easy to change int from 16 to 32 bit, for example. The first C/C++ compilers for Windows were using 16-bit integers. It was only in the mid to late 1990’s that Windows got a 32-bit API, and up until that point, you were using int that was 16-bit. Imagine that you have a well-working program that uses several hundred int variables, and all of a sudden, you have to change ALL of those variables to something else… Wouldn’t be very nice, right – especially as SOME of those variables DON’T need changing, because moving to a 32-bit int for some of your code won’t make any difference, so no point in changing those bits.

It should be noted that WCHAR is NOT the same as const char – WCHAR is a “wide char” so wchar_t is the comparable type.

So, basically, the “define our own type” is a way to guarantee that it’s possible to change the underlying compiler architecture, without having to change (much of the) source code. All larger projects that do machine-dependant coding does this sort of thing.