Program should have independent user defined function for each case.

Program:

#include<stdio.h>

#include<conio.h>

void main()

{

    int operator,ans;

    double firstNumber,secondNumber;

    clrscr();

    do

    {

        printf("Enter aoperation:\n1.Addition\n2.Subtraction\n3.Multiplication\n4.Divison");

        scanf("%d", &operator);

        printf("Enter two operands: ");

        scanf("%lf %lf",&firstNumber, &secondNumber);

        switch(operator)

        {

            case 1:

            printf("%.1lf + %.1lf = %.1lf",firstNumber, secondNumber, firstNumber + secondNumber);

            break;

            case 2:

            printf("%.1lf -%.1lf = %.1lf",firstNumber, secondNumber, firstNumber -secondNumber);

            break;

            case 3:

            printf("%.1lf * %.1lf = %.1lf",firstNumber, secondNumber, firstNumber * secondNumber);

            break;

            case 4:

            printf("%.1lf / %.1lf = %.1lf",firstNumber, secondNumber, firstNumber / secondNumber);

            break;

            default:

            printf("Error! operator is not correct");

        }

        printf("\nDo you want to continue 1.YES 2. NO");

        scanf("%d",&ans);

    }

    while(ans==1);

    getch();

}

Output:

Enter an Operation:

1.Addition

2.Subtraction

3.Multiplication

4.Division

1

Enter two operands 10 20

10.0 + 20.0 = 30.0

Do you want to continue 1.YES 2.NO 1

Enter an operation

1.Addition

2.Subtraction

3.Multiplication

4.Division

2

Enter two operands: 50 60

50.0 –60.0 = -10.0

Do you want to continue 1.YES 2.NO 2