21.Design a calculator.

//Design a calculator.
#include<stdio.h>
#include<conio.h>

void main()
{
    double number_1, number_2;
    char operation;

    clrscr();

    printf("Enter an expression: ");
    scanf("%lf%c%lf", &number_1, &operation, &number_2);

    switch(operation) {
        case '+':
            printf("%lf", number_1 + number_2);
            break;
        case '-':
            printf("%lf", number_1 - number_2);
            break;
        case '*':
            printf("%lf", number_1 * number_2);
            break;
        case '/':
            printf("%lf", number_1 / number_2);
            break;
        default:
            printf("Invalid operation.");
    }

    getch();
}