Library Functions in C programming language

Library functions are the inbuilt function in C that are grouped and placed at a common place called the library. Such functions are used to perform some specific operations. For example, printf is a library function used to print on the console. The library functions are created by the designers of compilers. All C standard library functions are defined inside the different header files saved with the extension .h. We need to include these header files in our program to make use of the library functions defined in such header files.

The list of mostly used header files is given in the following table.
Header File Description
stdio.h This is a standard input/output header file. It contains all the library functions regarding standard input/output.
conio.h This is a console input/output header file.
string.h It contains all string related library functions like gets(), puts(),etc.
stdlib.h This header file contains all the general library functions like malloc(), calloc(), exit(), etc
math.h This header file contains all the math operations related functions like sqrt(), pow(), etc.
time.h This header file contains all the time-related functions.
ctype.h This header file contains all character handling functions.
locale.h This file contains locale functions.