In C, it is possible for the functions to call themselves. A function is called ‘recursive’ if a statement within the body of a function calls the same function. Sometimes called ‘circular definition’, recursion is thus the process of defining something in terms of itself
Let us now see a simple example of recursion. Suppose we want to calculate the factorial value of an integer. As we know, the factorial of a number is the product of all the integers between 1 and that number. For example, 4 factorial is 4 * 3 * 2 * 1. This can also be expressed as 4! = 4 * 3! where ‘!’ stands for factorial. Thus factorial of a number can be expressed in the form of itself. Hence this can be programmed using recursion. However, before we try to write a recursive function for calculating factorial let us take a look at the non-recursive function for calculating the factorial value of an integer
main( )
{
int a, fact ;
printf ( “\nEnter any number ” ) ;
scanf ( “%d”, &a ) ;
fact = factorial ( a ) ;
printf ( “Factorial value = %d”, fact ) ;
}
factorial ( int x )
{
int f = 1, i ;
for ( i = x ; i >= 1 ; i– )
f = f * i ;
return ( f ) ;
}
And here is the output…
Enter any number 3
Factorial value = 6