Macro |
If a library routine is implemented as a macro, the macro definition appears in a header file. For instance, the toupper macro is defined in the header file CTYPE.H. |
Manifest constant |
Many library routines refer to constants that are defined in header files. For instance, the _open routine uses constants such as _O_CREAT, which is defined in the header file FCNTL.H. |
Type definition |
Some library routines return a structure or take a structure as an argument. For example, stream input/output routines use a structure of type FILE, which is defined in STDIO.H. |