#include <stdio.h>
int main()
{
    char operator;
    double num1, num2, sum, mult, div, subtract, percentage;
    

    do
    {
        printf("Enter a operator :\n");
        printf("Click ' ' for Addition\n");
        printf("Click '-' for Subtraction\n");
        printf("Click '*' for Multiplication\n");
        printf("Click '/' for Division\n");
        printf("Click '%%' for Percentage\n");
        printf("Click '0' for Exit\n");
        scanf("%c", &operator);
        printf("Enter any two numbers\n");
        scanf("%lf%lf", &num1, &num2);

        switch (operator)
        {
        case (' '):
            sum = num1   num2;
            printf("The sum of %.2lf and %.2lf is %.2lf\n", num1, num2, sum);
            break;
        case ('-'):
            subtract = num1 - num2;
            printf("The substraction of %.2lf and %.2lf is %.2lf\n", num1, num2, subtract);
            break;
        case ('*'):
            mult = num1   num2;
            printf("The multiplication of %.2lf and %.2lf is %.2lf\n", num1, num2, mult);
            break;
        case ('/'):
            div = num1 / num2;
            printf("The division of %.2lf and %.2lf is %.2lf\n", num1, num2, div);
            break;
        case ('%'):
            percentage = (num1 / num2) * 100;
            printf("The percentage of %.2lf and %.2lf is %.2lf %%\n", num1, num2, percentage);
            break;
        default:
            printf("Invalid number, try a valid number\n");
        }
    } while (operator!= '0');

    return 0;
}

What did I try?

• I am trying to make a repeating calculator program using switch case and do while loop (for repeating the same program.)

What am I expecting?

• I am expecting the calculator to repeat and ask the user whether the user wants to continue using the calculator or not.

What in reality is happening?

• At 1st compilation, everything works properly and the calculator runs. But, during the second compilation, the program is not scanning 'operator' and directly jumping to 'enter the numbers'.

CodePudding user response：

As already answered by Johnny Mopp and Andreas Wenzel, your scanf("%c", &operator); call reads the newline (\n) from the scanf("%lf%lf", &num1, &num2); that ran in the previous iteration of the loop.

You can change the call to include a space before the %c specifier in the format string to allow the scanf() function to skip any leading whitespace characters in the input buffer.

It should look like the following:

scanf(" %c", &operator);

Additionally, in your multiplication calculation, you used the operator instead of *.