C Standard library functions or C Library functions are inbuilt functions in C programming that will help us access functions. The prototype and the definitions of the functions are stored in their respective header files. Therefore, to access an inbuilt function in C, you need to include the header file in your C file.
One example is the printf() function that is accessible because we include the header
file library stdio.h on top of our program.
These are some examples of the C Library header files and link to its documentation.
| C Header File | Description | Some Function Examples |
|---|---|---|
| <assert.h> | Program assertion functions | assert() |
| <ctype.h> | Character type functions | isalnum(), isdigit(), tolower() |
| <locale.h> | Localization functions | setlocale() |
| <math.h> | Mathematics functions | log(), sqrt(), sin(), cos() |
| <setjmp.h> | Jump functions | setjmp(), longjmp() |
| <signal.h> | Signal handling functions | signal(), raise() |
| <stdarg.h> | Variable arguments handling functions | va_start(), va_arg() |
| <stdio.h> | Standard Input/Output functions | scanf(), printf(), getchar() |
| <stdlib.h> | Standard Utility functions | abort(), exit() |
| <string.h> | String handling functions | strcpy(), strcat(), strncat() |
| <time.h> | Date time functions | difftime(), time(), clock() |