Lesson 3.2. modulo

Modulo

The modulo is the remainder of the whole division. Let's take the example of the division of 618 by 4 :

The result of the integer division of 618 by 4 is 154. The remainder of the integer division is 2.

Note: the operands of the modulo must be integers.

Example

The modulo is a very common operator in computer science. It allows for example to test if a number is even or odd :

if the number is even, the remainder of the division by 2 is zero;
if the number is odd, the remainder of the division by 2 is one.

Here is an example of a program that tests the parity of the variable number (we will come back to this in detail later):

// Check if the number is even or odd
if (number % 2 == 0) 
  printf ("It is an even number");
else
  printf ("It is an odd number");

Exercise

We want to build a fence of 12345 centimeters. This fence is made with panels of 125 centimeters. Complete the program below to calculate the length that will remain to be fenced after the panels are installed.

#include <stdio.h>

int main(void) {
    int length = 12345;
    int pannels = 125;
    int remainder;

    // Calculate the remainder to be fenced
    // COMPLETE HERE

    printf ("%d cm left to fence.\n", remainder);
    return 0;
}

Do the exercise

Solution

Quiz

What is the modulo operator (%)?

The integer part of the result of a division

The operator to calculate percentages

The remainder of the integer division

The remainder of the division with floating numbers.

Check

What can the modulo operator be used for?

To determine if a number is even or odd.

To determine if a number is divisible by another.

To divide two integers.

To specify the precision of a calculation.

Check

What will the variable x contain after the next line?

x = 12 % 4 ;

Check

What can the variable x contain?

x = b % 3 ;

Check

How to isolate the number of units of the variable x?

unit = 9 % x;

unit = x % 9;

unit = 10 % x;

unit = x % 10;

Check

How to isolate the tens digit of the variable x?

dozen = x % 100;

dozen = (x/10) % 10;

dozen = (x%10) / 10;

dozen = (x%100) / 10;

Check

Lesson 3.1 Summary Lesson 3.3

Lesson 3.2. modulo

Modulo

Example

Exercise

Quiz

See also