Windows 3 supports over 550 function calls that applications can use. It is highly unlikely that you will ever memorize the syntax to all these calls. Most Windows programmers keep the Windows Programmer's Reference manual within easy reach.
Each of the Windows functions has a descriptive name written in mixed uppercase and lowercase letters, such as CreateWindow. This function (as you might guess) creates a window for your program. Another example: the function IsClipboardFormatAvailable determines whether the clipboard is holding data of a particular format.
All the Windows functions are declared in a header file named WINDOWS.H, included in the Windows Software Development Kit. WINDOWS.H is an important part of the Windows documentation. You might want to print a copy or use a file browser for quick reference.
You use these Windows functions in your Windows program the same way you use C library functions such as strlen. However, there are some differences between the Windows functions and the standard C library functions.
Windows functions are always declared as far pascal functions. These are two keywords that Microsoft has added to its version of C. The far keyword indicates that the Windows function is in a different code segment than the program's code. (You'll see the reason for this shortly.)
The pascal keyword indicates that the function's calling sequence is different than the normal C calling sequence. Normally, the C compiler generates code that pushes parameters on the stack from right to left beginning with the last parameter. The code calling the function is responsible for adjusting the stack pointer after the function returns. With the pascal calling sequence, the parameters are pushed on the stack from left to right and the called function cleans up the stack. The pascal calling sequence is used in Windows because it is more efficient.
With one oddball exception, any pointer passed to a Windows function must be a far pointer. This is something you normally don't have to worry about because the compiler will extend short pointers to long pointers based on the function template in WINDOWS.H.