Replacement for goto in switch case

Question

I have written this code to perform multiple mathematical operation, with main menu to select the operation, and repeat it until you want and revert back to main menu. I have looped it using switch case and go-to. I want to replace the go-to, and want suggestions regarding how can I make it function in same way without using go-to. Thank you.

//I want the program of be infinite until you want to exit.Thus I used goto to continuously loop it back to either main menu or the mathematical operation you are in. 
#include<conio.h>
#include<stdio.h>
#include<stdlib.h>

int a,b,i,num,n;
char rep;
void main (void)

{
//main menu-(main:-for goto function)
main:
{
printf("\nMAIN MENU\n\n1. Factorial\n2. Sum\n3. Odd/Even\n4. Prime Number\n5. Multiplication\n6. Exit\n");
scanf("%d", &n);
}
switch (n)
{
    case 1:
        {
            fact:
            {
            printf("Number- ");
            scanf("%d", &num);
            a=1;
        for(i=1;i<=num;i++)
        {
            a=a*i;
            continue;
        }
        printf("\nFactorial of %d= %d\n\n", num, a);

//This is how I loop it back to main menu or for repeating the mathematical operation using combination of conditional operators and goto.
        printf("Repeat? y/n- ");
        fflush(stdin);
        scanf("%c", &rep);
        (rep=='y')?({goto fact;}):({goto main;});
        }
        }
    case 2:
        {
            sum:
            {
                a=0;
            printf("Value of repetitions- ");
            scanf("%d", &num);
            printf("Enter Digits to sum:\n");

            for(i=1;i<=num;i++)
            {
                scanf("%d", &b);
                printf("+ ");
                a=a+b;
                continue;
            }
            printf("\nThe Sum of Digits= %d\n\n", a);
            printf("Repeat? y/n- ");
            fflush(stdin);
            scanf("%c", &rep);
            (rep=='y')?({goto sum;}):({goto main;});
            }
        }

    case 3:
        {
            oe:
            {
                printf("Enter a Number- ");
                scanf("%d", &a);
                (a%2==0)?(printf("\n%d is an Even Number\n",a)):(printf("\n%d is an Odd number\n", a));
            printf("\nRepeat? y/n- ");
            fflush(stdin);
            scanf("%c", &rep);
            (rep=='y')?({goto oe;}):({goto main;});
            }
        }
    case 4:
        {
            prime:
                {
                    printf("\nEnter a Number- ");
                    scanf("%d",&num);
                    if(num==2)
                        printf("\n\n%d is a Prime Number\n\n", num);

                    for(i=2;i<=num-1;i++)
                    {

                        (num%i==0)?({printf("\n\n%d is Not a Prime Number.\n\n", num);break;}):({printf("\n\n%d is a Prime Number\n\n", num);break;});

                    }

                    printf("\nRepeat? y/n- ");
                    fflush(stdin);
            scanf("%c", &rep);
            (rep=='y')?({goto prime;}):({goto main;});
                }

        }
    case 5:
        {
            mul:
            {
                a=1;
            printf("Value of repetitions- ");
            scanf("%d", &num);
            printf("Enter Digits to multiply:\n");

            for(i=1;i<=num;i++)
            {
                scanf("%d", &b);
                printf("* ");
                a=a*b;
                continue;
            }
            printf("\nThe Multiplication of Digits= %d\n\n", a);
            printf("Repeat? y/n- ");
            fflush(stdin);
            scanf("%c", &rep);
            (rep=='y')?({goto mul;}):({goto main;});
            }
        }
//Case 6 is only for aesthetic reasons.
        case 6:
        printf("\n\nPress Enter\n\n");
}
}

Answer 1

Considering the fact that you do not want to change your program in any way other than the goto function, you can put your entire code under a do while loop, a while loop or a for loop like this:

do {
....
} while(rep != 'y')