### 13.2 Traditional macros, `varargs.h`

If your C compiler predates ANSI C, you may still be able to use variable argument lists using the macros from the `varargs.h` header file. These macros resemble their ANSI counterparts, but have important differences in usage. In particular, since traditional C has no declaration mechanism for variable argument lists, two additional macros are provided simply for the purpose of defining functions with variable argument lists.

As with `stdarg.h`, the type `va_list` is used to hold a data structure representing a variable argument list.