Problem 7.1,Let Us C Solution

  Write a menu driven program which has following options:

1.Factorial of a number
2.Prime or not
3.Odd or even
4.Exit
Once a menu item is selected the appropriate action should be taken
and once this action is finished,the menu should reappear.Unless the
user selects the 'Exit'option the program should continue to work.  */
#include<stdio.h>
#include<stdlib.h>
int main()
{
	int choice,num,i,fact;
	while(1)
	{
		printf("\n1.Factorial\n");
		printf("2.Prime\n");
		printf("3.Odd/Even\n");
		printf("4.Exit\n");
		printf("Your choice?");
		scanf("%d",&choice);
		switch (choice)
		{
			case 1:
				printf("\nEnter number:");
				scanf("%d",&num);
				fact=1;
				for(i=1;i<=num;i++)
				fact=fact*i;
				printf("Factorial value=%d\n",fact);
				break;
				
				case 2:
					printf("\nEnter number:");
					scanf("%d",&num);
					for(i=2;i<num;i++)
					{
						if(num%i==0)
						{
							printf("Not a prime number\n");
							break;
						}
					}
					if(i==num)
					printf("Prime number\n");
					break;
					case 3:
						printf("\nEnter number:");
						scanf("%d",&num);
						if(num %2==0)
						printf("Even number\n");
						else 
						printf("Odd number\n");
						break;
						case 4:
							exit(0);// Terminates program execution
							default :
								printf("Wrong choice\a\n");
		}
	}
	return 0;
}