#include<stdio.h>
/* function prototype */
void factorial(int);
void prime(int);
void even_odd(int);

main()
{
    int i, num1, choice, x;
    while(1)
    {
       printf("Menu is below: \n"); 
       printf("1.  Factorial\n");     
       printf("2.  Prime\n");
       printf("3.  Even/odd\n");
       printf("4.  Exit\n");
       printf("Enter your choice : \t");
       scanf("%d", &choice);
       printf("Enter a number \t");
       scanf("%d", &x);
       switch(choice)
       {
           case 1:
                factorial(x);  // function call
                break;
           case 2:
                prime(x);   // function call
                break;
           case 3:
                even_odd(x);   // function call
                break; 
           case 4:
                exit(0);
           default:
                printf("Input choice is wrong. \n");                                
       }// switch     
    } //while(1)
    system ("pause");
}
void factorial (int num)
{
   int i, f=1;
   //printf("Enter a number to find a factorial \t");
   //scanf("%d", &num);
   for(i= num; i>1; i--)
       f=f*i;
   printf("Factorial = %d\n",f);            
}// factorial function closing
void prime(int num)
{
    int i;
    //printf("Enter a number \t");
    //scanf("%d", &num);
    i=2;
    while(i <= (num/2))
    {
        if(num % i == 0)
        {
            printf("Number is not prime \n");
            break;       
        }   
        i++;          
    }
    if(i == (num/2+1))
       printf("Number is prime \n");
}// prime function closing
void even_odd(int num)
{
   int x;
   //printf("Enter a number \n");
   //scanf("%d", &x);
   if(num%2 == 0)
      printf("Even number \n");
   else
      printf("Odd number \n");        
} // prime_odd function closing