What is H? H, short name for Header, is used as the file extension for C Header files. .H files are text files that can be opened by Notepad or any text editors. See the sample .H file included below.

File Extension: .H

MIME Type: text/plain

File Content: C Header

.H files are C Header files, which contain forward declarations of classes, subroutines, variables, and other identifiers. Here is a sample .H C Header file, stdio.h, containing some declarations:

#ifndef _INC_STDIO
#define _INC_STDIO

#define __NEEDS_SIZE_T 1
#define __NEEDS_EXTERN_C 1
#define __NEEDS_NULL 1
#include <__defs.h>

/* FILE type and predefined file handles
 */
typedef struct _FILE FILE, *PFILE;

EXTERN_C FILE * __cdecl __stdfile(int);
#define stdin  (__stdfile(0))
#define stdout (__stdfile(1))
#define stderr (__stdfile(2))

/* File position
 */
typedef UINT64 fpos_t;

/* Constants for setvbuf
 */
#define _IOFBF  0
#define _IOLBF  1
#define _IONBF  2
...

.H C Header file sample: Click sample.h to download.

Since .H text files are in text format, you can use Notepad or any text editor to create or modify them. No special software is needed.

For for information on how to use .H C Header files, see links below:

• The C Library Reference Guide