Library functions are built-in functions that are grouped together and placed in a common location called library.

Each function here performs a specific operation. We can use this library functions to get the pre-defined output.

All C standard library functions are declared by using many header files. These library functions are created at the time of designing the compilers.

We include the header files in our C program by using #include<filename.h>. Whenever the program is run and executed, the related files are included in the C program.

Library Functions in Different Header Files

Some of the header file functions are as follows −

  • stdio.h− It is a standard i/o header file in which Input/output functions are declared
  • ctype.h - Character type functions
  • conio.h− This is a console input/output header file.
  • string.h− All string related functions are in this header file.
  • stdlib.h− This file contains common functions which are used in the C programs.
  • math.h− All functions related to mathematics are in this header file.
  • time.h− This file contains time and clock related functions. Built functions in stdio.h
  • stdarg.h - Variable arguments handling function
  • signal.h - Signal handling functions
  • locale.h - Localization functions
  • assert.h - Program assertion functions

Advantages of Using C library functions

1. They work

One of the most important reasons you should use library functions is simply because they work. These functions have gone through multiple rigorous testing and are easy to use.

2. The functions are optimized for performance

Since, the functions are "standard library" functions, a dedicated group of developers constantly make them better. In the process, they are able to create the most efficient code optimized for maximum performance.

3. It saves considerable development time

Since the general functions like printing to a screen, calculating the square root, and many more are already written. You shouldn't worry about creating them once again.

4. The functions are portable

With ever-changing real-world needs, your application is expected to work every time, everywhere. And, these library functions help you in that they do the same thing on every computer.