Header files
Each
standard library has a corresponding header containing the function prototype
for all the functions in that library, definitions of various data types and
constants needed by those functions.
Programmer-defined
headers should also use the .h filename extension.
A
programmer-defined header can be included by using the #include pre-processor
directive. For example, the prototype for square function is located in the
header square.h, then we include this
header in the program by using the following directive at the top of the
program:
#include
“square.h”
<assert.h>:
contains macros and information for adding diagnostics that aid program
debugging.
<ctype.h>:
contains function prototypes for functions that test characters for certain
properties, and function prototypes for function that can be used to convert
lowercase letters to uppercase letters and vice versa.
<errno.h>:
defines macros that are useful for reporting error conditions.
<float.h>:
contains the floating – point size limits of the system.
<limits.h>:
contains he integral size limits of the system.
<locale.h>:
contains function prototypes and other information that enables a program to be
modified for the current locale on which it’s running. The notion of locale
enables the computer system to handle different conventions for expression data
like data, time, dollar amounts and large numbers throughout the world.
<math.h>:
contains function prototypes for math library functions.
<setjmp.h>:
contains function prototypes for function that allow bypassing of the usual
function call and return sequence.
<signal.h>:
contains function prototypes and macros to handle various conditions that may
arise during program execution.
<stdarg.h>:
defines macros for dealing with a list of arguments to a function, whose number
and types are unknown.
<stddef.h>:
contains common type definitions used by C for performing calculations.
<stdio.h>:
contains function prototypes for the standard input/output library functions,
and information used by them.
<stdlib.h>:
contains function prototypes for conversions of numbers to text and text to
numbers, memory allocation, random numbers and other utility functions.
<string.h>:
contains function prototypes for string – processing functions.
<time.h>:
contains function prototypes and types for manipulating the time and date.
