Factorial of a number using Recursion

 Let Fact (n) be the function which calculates the factorial of n

                                                If n=0, then n! =1

Fact (n) =

                                                If n>0, then n! =n. (n-1)!

that is, Fact (6) =6*Fact(5)

                        Fact (5) =5*Fact (4)

                                 Fact (4) =4*Fact (3)

                                                Fact (3) =3*Fact (2)

                                                                                Fact (2) =2*Fact (1)

                                                                                                Fact (1) =1*Fact (0)

                                                                                                Fact (1) =1*1=1

                                                                                Fact(2) =2*1=2

                                                                Fact (3) =3*2=6

                                                Fact (4) =4*6 =24

                                Fact (5) =5*24=120

                Fact (6) =6*120=720

Write a program to calculate the factorial of the given number by using the recursion function.

#include<stdio.h>

#include<conio.h>

int fact(int num)

{

                if(num==0)

                                return(1);

                else

                                return(num*fact(num-1));

}

void main()

{

                int num;

                int factorial;

                clrscr();

                printf("Enter any number to calculate factorial:");

                scanf("%d",&num);

                factorial=fact(num);

                printf("Factorial is:%d",factorial);

                getch();

}

Output: Enter any number to calculate factorial:6

                 Factorial is: 720