C Related File Extensions

The following table lists the standard file extensions used for C-related files. The extension normally indicates how far the file is through the compilation process. Note that many integrated development environments (IDEs), and command-line compilers hide most of the individual compiler steps from the user.

File Extension	Description
file-name.c	C source code which must be preprocessed.
file-name.i	C source code which should not be preprocessed.
file-name.h	C header file (not to be compiled or linked).
file-name.s	Assembler code.
file-name.S	Assembler code which must be preprocessed.
file-name.o	Object file by default, the object file name for a source file is made by replacing the extension .c, .i, .s etc with .o. This can be changed with a command line parameter.
file-name	If the file has no extension, this is usually the final executable (NIX systems).
file-name.exe, .dll, .com	The final executable on a Windows system.