Library Functions in C

When it comes to the programming world, library functions play an important role. Library functions help the programming language to perform desirable actions. When it comes to a competitive examination like GATE, you have to read the whole topic quite deeply. In this article, we have covered all the topics relevant to the library functions in C. We hope the notes for the CSE topics will help you understand this topic in a better way.

What is Library Functions in C?

All the programming languages contain functions. Library functions in C are also inbuilt functions in C language.

These inbuilt functions are located in some common location, and it is known as the library. All the functions are used to execute a particular operation. These library functions are generally preferred to obtain the predefined output. Also, the actions of these functions are present in their header files.

Library Functions in Different Header Files

Here in this table-picture, there are some header files with their meanings.

Header file Description
stdio.h This is standard input/output header file in which Input/Output functions are declared
conio.h This is console input/output header file
string.h All string related functions are defined in this header file
stdlib.h This header file contains general functions used in C programs
math.h All maths related functions are defined in this header file
time.h This header file contains time and clock related functions
ctype.h All character handling functions are defined in this header file
stdarg.h Variable argument functions are declared in this header file
signal.h Signal handling functions are declared in this file
setjmp.h It includes all jump functions
locale.h It includes locale functions
errno.h Error handling functions are given in this file
assert.h It includes diagnostics functions

Advantages of Using C library Functions

1. The Execution: One of the most significant reasons for utilising the library functions is that these functions are easy-to-use, and have gone through strict testing.

2. The Functions to Boost the Performance: The standard library functions are very popular. And, that is the reason developers are trying their best to polish them. During this process, they come up with an efficient code almost every time to boost the performance.

3. Can Save a Lot of Time: The best part is you don’t need to create basic functions, like calculating the square root and more, because we already have these. So, the conclusion is, we can save a lot of time here.

4. These Functions are Convenient: The best quality of an application is that it should work every time and everywhere. These library functions assist you in this particular phenomenon.

Example of Library Function: Using sqrt

#include <stdio.h>

#include <math.h>

int main(int argc, const char * argv[])


/* Explain temporary variables */

double value;

double result;

/* Provide the value we will find the sqrt of */

value = 36;

/* Determine the square root of value */

result = sqrt(value);

/* Show the result of the calculation */

printf(“The Square Root of %f is %f\n”, value, result);

return 0;


Output: The Square Root of 36.000000 is 6.000000

Practice Problems – Library Functions in C

Q. Consider the following C program:

#include <stdio.h>

int main(){

int arr[]={1,2,3,4,5,6,7,8,9,0,1,2,5}, *ip=arr+4;

printf(“%d\n”, ip[1]);

return 0;


The number that will be displayed on execution of the program is ___________ .

Q. Consider the following C program:

#include <stdio.h>

int r(){

static int num=7;

return num–;


int main(){

for (r();r();r())


return 0;


Which one of the following values will be displayed on execution of the programs?

  • (A) 41
  • (B) 52
  • (C) 63
  • (D) 630

FAQs – Library Functions in C

What is the Library function in C?

Library functions in C are also inbuilt functions in the C language.

What is the role of studio.h?

It is a typical input/output header file in which all the functions are communicated or declared.

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