C program to find factorial of a number using recursion :

#include< stdio.h >
#include< conio.h >
void main()
{
          int num,factorial;
          int fact (int num);
          clrscr();
          printf("Enter a number:");
          scanf("%d",&num);
          factorial=fact(num);
          printf("Factorial=%d",factorial);
          getch();
}
int fact (int num)
{
         if(num==1)
         return 1;
         else
         return (num * fact (num-1));
}

OUTPUT :

Enter a number : 5
Factorial=120