C Library - < stdlib.h >

The stdlib.h header defines four variable types, several macros, and various functions for performing general functions.

Library Variables

Following are the variable types defined in the header stdlib.h −

Sr.No.	Variable & Description
1	size_t This is the unsigned integral type and is the result of the sizeof keyword.
2	wchar_t This is an integer type of the size of a wide character constant.
3	div_t This is the structure returned by the div function.
4	ldiv_t This is the structure returned by the ldiv function.

Library Macros

Following are the macros defined in the header stdlib.h −

Sr.No.	Macro & Description
1	NULL This macro is the value of a null pointer constant.
2	EXIT_FAILURE This is the value for the exit function to return in case of failure.
3	EXIT_SUCCESS This is the value for the exit function to return in case of success.
4	RAND_MAX This macro is the maximum value returned by the rand function.
5	MB_CUR_MAX This macro is the maximum number of bytes in a multi-byte character set which cannot be larger than MB_LEN_MAX.

Library Functions

Following are the functions defined in the header stdio.h −

Sr.No.	Function & Description
1	double atof(const char *str) Converts the string pointed to, by the argument str to a floating-point number (type double).
2	int atoi(const char *str) Converts the string pointed to, by the argument str to an integer (type int).
3	long int atol(const char *str) Converts the string pointed to, by the argument str to a long integer (type long int).
4	double strtod(const char *str, char **endptr) Converts the string pointed to, by the argument str to a floating-point number (type double).
5	long int strtol(const char *str, char **endptr, int base) Converts the string pointed to, by the argument str to a long integer (type long int).
6	unsigned long int strtoul(const char *str, char **endptr, int base) Converts the string pointed to, by the argument str to an unsigned long integer (type unsigned long int).
7	void *calloc(size_t nitems, size_t size) Allocates the requested memory and returns a pointer to it.
8	void free(void *ptr Deallocates the memory previously allocated by a call to calloc, malloc, or realloc.
9	void *malloc(size_t size) Allocates the requested memory and returns a pointer to it.
10	void *realloc(void *ptr, size_t size) Attempts to resize the memory block pointed to by ptr that was previously allocated with a call to mallocor calloc.
11	void abort(void) Causes an abnormal program termination.
12	int atexit(void (*func)(void)) Causes the specified function func to be called when the program terminates normally.
13	void exit(int status) Causes the program to terminate normally.
14	char *getenv(const char *name) Searches for the environment string pointed to by name and returns the associated value to the string.
15	int system(const char *string) The command specified by string is passed to the host environment to be executed by the command processor.
16	void *bsearch(const void *key, const void *base, size_t nitems, size_t size, int (*compar)(const void *, const void *)) Performs a binary search.
17	void qsort(void *base, size_t nitems, size_t size, int (*compar)(const void *, const void*)) Sorts an array.
18	int abs(int x) Returns the absolute value of x.
19	div_t div(int numer, int denom) Divides numer (numerator) by denom (denominator).
20	long int labs(long int x) Returns the absolute value of x.
21	ldiv_t ldiv(long int numer, long int denom) Divides numer (numerator) by denom (denominator).
22	int rand(void) Returns a pseudo-random number in the range of 0 to RAND_MAX.
23	void srand(unsigned int seed) This function seeds the random number generator used by the function rand.
24	int mblen(const char *str, size_t n) Returns the length of a multibyte character pointed to by the argument str.
25	size_t mbstowcs(schar_t *pwcs, const char *str, size_t n) Converts the string of multibyte characters pointed to by the argument str to the array pointed to by pwcs.
26	int mbtowc(whcar_t *pwc, const char *str, size_t n) Examines the multibyte character pointed to by the argument str.
27	size_t wcstombs(char *str, const wchar_t *pwcs, size_t n) Converts the codes stored in the array pwcs to multibyte characters and stores them in the string str.
28	int wctomb(char *str, wchar_t wchar) Examines the code which corresponds to a multibyte character given by the argument wchar.