Question

int countBouncy=5;
int count=999899;

double percent = (double)(countBouncy / count) * 100.0;

The result of that phrase is unexpected, I get zero.

Why won’t it work?

Answer 1

You are doing an integer division on (countBouncy / count). Change your code to

double percent = ((double)countBouncy / count) * 100.0;

That way, countBouncy is converted to double explicitly and count is converted to double implicitly by the c# compiler to make it compatible to the (now double) countBouncy.

Otherwise (countBouncy / count) is calculated as (5 / 999899) --> 0 since both are integers.

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How does integer division work? Let’s take an example:

7 / 2 = 3

Integer division drops the decimal part that a real division would yield. The result is truncated towards zero. You can get the remainder of this division by using the modulo operator

7 % 2 = 1

and perform the backward calculation like this

2 * (7 / 2) + 7 % 2 = 7

You can enter this in the immediate window of Visual Studio to test it:

?2 * (7 / 2) + 7 % 2<enter>
7