#define

The #define directive defines a preprocessor macro.

#define macro-name <[>(arg<[>, arg ...<]>)<]> replacement-text

You may use #define to create function-like macros with or without arguments. Macros are syntactically similar to function calls. When a defined macro is encountered in the source file, the macro-name and any arguments are replaced by the replacement-text. For example:

#define my_macro(a,b,c) a+b+c

int func (int x, int y, int z)
{
return(my_macro(x,y,z));
}

appears as follows after macro expansion:

int func (int x, int y, int z)
{
return(x+y+z);
}

Refer to Macros for a complete description of how to define and use macros in your C programs.