c++ - what is FAR PASCAL?

Question

I was wondering why in some source code there are these macros like FAR and PASCAL. What do they mean and do?

Answer 1

• PASCAL: It's related to a calling convention. The parameters are pushed on the stack in left-to-right order (opposite of cdecl), and the callee is responsible for balancing the stack before return.

  This calling convention was common in the following 16 bit APIs: OS/2 1.x and Microsoft Windows 3.x. There's some dispute over whether it was used by Borland Delphi 1.x

• FAR: In a segmented architecture computer, a far pointer is a pointer which includes a segment selector, making it possible to point to addresses outside of the current segment.

For completeness, FAR and PASCAL are prepreocessor macros that, when compiled for 16-bit systems, expand to the keywords that were necessary to declare the calling convention and pointer size. On 32-bit systems, they generally expand to nothing (unless you have a weird default calling convention). The macros are retained for backward compatibility {hat/tip: comment from Adrian McCarthy}