c: modulus operator

The modulus operator (%) gives the remainder of two divided numbers. For instance, consider the following portion of code:
x = 15/7
If x were an integer, the resulting value of x would be 2. However, consider what would happen if you were to apply the modulus operator to the same equation:
x = 15%7
The result of this expression would be the remainder of 15 divided by 7, or 1. This is to say that 15 divided by 7 is 2 with a remainder of 1.

The modulus operator is commonly used to determine whether one number is evenly divisible into another.

For instance, if you wanted to print every third letter of the alphabet, you would use the following code:
int x;
for (x=1; x<=26; x++)
if ((x%3) == 0)
printf(“%c”, x+64);