How to only display decimal points to 2 decimal places only when there aren't trailing zeroes

Question

I've been trying to to display decimal points to 2 decimal places for a multiplication operation:

if (operation == multiplication)
    {
        printf("\n\n            You have chosen to perform a multiplication operation\n\n");
        printf("Please enter two numbers seperated by a space (num1 * num2): ");
        scanf("%f %f", &number1, &number2);

        total = number1 * number2;

        printf("\n%f times %f is equal to: %f", number1, number2, total);
    }

so if I enter 0.5 & 30 I'll get 15 and not 15.000000 and if I enter 0.5 & 15 I'll get 7.50 and not 7.5000000.

I'm still quite new to programming in C and in general as well, so detailed explanations would really be great. Thanks.

David Ranieri · Accepted Answer · 2015-02-27T12:51:09.550

3

Use printf with precision specifier:

#include <stdio.h>
#include <math.h>

int main(void)
{
    double x = 10.0, y = 10.5, dummy;

    printf("%.*f\n", (modf(x, &dummy) == 0) ? 0 : 2, x);
    printf("%.*f\n", (modf(y, &dummy) == 0) ? 0 : 2, y);
    return 0;
}

Output:

10
10.50

edited Feb 27 '15 at 12:51

answered Feb 27 '15 at 12:28

David Ranieri

39,972
7
52
94

is there anyway to make it fetch the values of x and y from the user? – Tamilore Simpson Mar 04 '15 at 11:38
You are already using this function (`scanf`) in your code snippet, why are you asking this? – David Ranieri Mar 04 '15 at 15:37

score 1 · Answer 2 · answered Feb 27 '15 at 12:21

Just specify the decimal places like this:

printf("\n%.2f times %.2f is equal to: %.2f", number1, number2, total); 
         //^^See here ^^                ^^

For more information about printf() see here: http://www.cplusplus.com/reference/cstdio/printf/

How to only display decimal points to 2 decimal places only when there aren't trailing zeroes

2 Answers2