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Recursive function in C programming language

Updated on May 28, 2012

We have learnt different types function C language and now I am going to explain recursive function in C. A function is called “recursive” if a statement within body of that function calls the same function for example look at below code:

void main()
{
printf(“recursive function called.\n”);
main();
}

When you will run this program it will print message “recursive function called.” indefinitely. If you are using Turbo C/C++ compiler then you need to press Ctrl + Break key to break this in definite loop.

Recursive function example output

Before we move to another example lets have attributes of “recursive function”:-

  1. A recursive function is a function which calls itself.
  2. The speed of a recursive program is slower because of stack overheads. (This attribute is evident if you run above C program.)
  3. A recursive function must have recursive conditions, terminating conditions, and recursive expressions.

Calculating factorial value using recursion

To understand how recursion works lets have another popular example of recursion. In this example we will calculate the factorial of n numbers. The factorial of n numbers is expressed as a series of repetitive multiplication as shown below:

Factorial of n = n(n-1)(n-2)……1.

Example :

          Factiorial of 5 = 5x4x3x2x1
                                 =120

#include<stdio.h>
#include<conio.h>

int factorial(int);

int factorial (int i)
{
	int f;
	if(i==1)
	return 1;
	else
	f = i* factorial (i-1);
return f;
}

void main()
{
	int x;
	clrscr();
	printf("Enter any number to calculate factorial :");
	scanf("%d",&x);
	printf("\nFactorial : %d", factorial (x));
	getch();
}

Factorial value using recursive function output

So from line no. 6 – 14 is a user defined recursive function “factorial” that calculates factorial of any given number. This function accepts integer type argument/parameter and return integer value. If you have any problem to understand how function works then you can check my tutorials on C function (click here).

In line no. 9 we are checking that whether value of i is equal to 1 or not; i is an integer variable which contains value passed from main function i.e. value of integer variable x. If user enters 1 then the factorial of 1 will be 1. If user enters any value greater than 1 like 5 then it will execute statement in line no. 12 to calculate factorial of 5. This line is extremely important because in this line we implemented recursion logic.

Let’s see how line no. 12 exactly works. Suppose value of i=5, since i is not equal to 1, the statement:

f = i* factorial (i-1);

will be executed with i=5 i.e.

f = 5* factorial (5-1);

will be evaluated. As you can see this statement again calls factorial function with value i-1 which will return value:

4*factorial(4-1);

This recursive calling continues until value of i is equal to 1 and when i is equal to 1 it returns 1 and execution of this function stops. We can review the series of recursive call as follow:

f = 5* factorial (5-1);

f = 5*4* factorial (4-1);

f = 5*4*3* factorial (3-1);

f = 5*4*3*2* factorial (2-1);

f = 5*4*3*2*1;

f = 120;

I hope this will clear any confusion regarding recursive function.

Your opinion

Did this help you to learn about recursion in C programming language?

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    • profile image

      shiva 3 years ago

      thank u

    • profile image

      deepika7893 4 years ago

      int f(int x)

      {

      if(x!=0)

      {

      f(x-1);

      printf("%d",x);

      }

      }

      void main()

      {

      int x=5;

      f(x);

      }

      send ans for ths n how does it get implement???

    • profile image

      deepika 4 years ago

      int f(int x)

      {

      if(x!=0)

      {

      f(x-1);

      printf("%d",x);

      }

      }

      void main()

      {

      int x=5;

      f(x);

      }

      send ans for ths n how does it get implement???

    • profile image

      snehal 4 years ago

      there are the pattern

      in the A

      2 B

      4 C 6

      D 8 E 10

      there program i am not parporaly writter ......... plze help me.

    • profile image

      Aditya Bhowmick 5 years ago

      THANKS SIR,

    • profile image

      manu 5 years ago

      really helpful for every one

    • profile image

      JAYPRAKASH 5 years ago

      THIS IS VERY GOOD EXPLANATION......

      types of recursion should b included!!

    • profile image

      BHOJESH.L.AHIR 5 years ago

      SIR,REALLY I NICE YOUR EXPLANATION.SO THAT I AM EVER OBLIGES YOU.

    • profile image

      sandeep 5 years ago

      good work

    • profile image

      Sonali Naik 5 years ago

      this is really helpful for beginners

    • profile image

      paritosh kumar 5 years ago

      really helpful

    • profile image

      sneha jha 5 years ago

      types of recursion should b included!!

    • profile image

      rey 5 years ago

      nice it is good...

    • profile image

      rheck 5 years ago

      how to 3 tries to exit???

    • profile image

      mart 5 years ago

      how to put a codes that displyaing all product to choice.

    • profile image

      rajeev singh 5 years ago

      nice explanation....

    • profile image

      sandeep choudhary 5 years ago

      nice

    • profile image

      saurabh 5 years ago

      this tutorial is awsome for beginners!!!!!

    • profile image

      suhani thakur 5 years ago

      very good explanation

    • profile image

      sree 5 years ago

      its nice god bless you

    • profile image

      Arnab Mallick, Bangalore 5 years ago

      Nice explanation...... good job bro !

    • profile image

      ASHA 6 years ago

      WHAT IS DIRECT, INDIRECT, TREE, & TAIL RECURTION?

    • profile image

      siddhu 6 years ago

      one small doubt: can we use function defination before main() heading i,,e before calling a function ,

    • profile image

      mallika 6 years ago

      very clear explanation

    • profile image

      Adam 6 years ago

      Good explanation well done

    • profile image

      Dharmendra kumar yadav 6 years ago

      hi

      sir nice job .it is very simple to understand .i understand

      with in 2 min recursive function . it means read and learn .

      nice ....................good job

    • profile image

      sahil green 6 years ago

      thanks it helped

    • profile image

      shilpa 6 years ago

      Very nice explanation........i understood very well.....can i get some more points nd programs which will be useful for my campus selection.

    • profile image

      sara 6 years ago

      write a recursive value that asks the user to enter a positive intger number each time it is called , until zero or negative number is input . the function then outputs the greatest number thus far as it outputs the number is reverse order . it returns the greatest value input . write a main program to call the function and prints the result .

    • profile image

      abhijit 6 years ago

      if we want to calculate the factorial of 0 den will d above program work as the terminating condition of the program is an if statement.

    • profile image

      nivedita 6 years ago

      it's realy useful

    • profile image

      saloni 6 years ago

      the data made available is to an extent variable and soothing

    • profile image

      karim 7 years ago

      very good

    • PDXBuys profile image

      PDXBuys 7 years ago from Oregon

      I wrote a recursive function using pointers and then my computer vanished down a black hole!

    • profile image

      Nikhil 7 years ago

      This tutorial is very much usefull

    • nicomp profile image

      nicomp really 7 years ago from Ohio, USA

      Great explanation of recursive functions. Well done.