By | 22.03.2017

C Program to display numbers from 1 to n and their sum by recursion

Write a C Program to display numbers from 1 to n and their sum. How to find sum of natural numbers in a given range in C programming. C program to find sum of natural numbers in given range. Logic to find sum of all natural numbers in a given range in C program.

Recursion : :

• Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
• The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
• Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

Below is the source code for C Program to display numbers from 1 to n and their sum by recursion which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

```/* Program to display numbers from 1 to n and their sum*/

#include<stdio.h>
int summation(int n);
void display1(int n);
void display2(int n);

int main( )
{
int n;
printf("Enter number of terms : ");
scanf("%d", &n);

display1(n);
printf("\n");

display2(n);
printf("\n");

printf("sum = %d\n", summation(n));

return 0;

}
/*End of main()*/

int summation( int n)
{
if(n==0)
return 0;
return ( n + summation(n-1) );
}/*End of summation()*/

/*displays in reverse order*/
void display1(int n)
{
if( n==0 )
return;
printf("%d ",n);
display1(n-1);
}/*End of display1()*/

void display2(int n)
{
if( n==0 )
return;
display2(n-1);
printf("%d ",n);
}/*End of display2()*/```

OUTPUT  : :

```//OUTPUT ::

Enter number of terms : 15
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

sum = 120

Process returned 0```

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