Floor Division in C#: Integer Division and Math.Floor

TL ; DR:

• The Math.Floor() function returns the largest integer less than or equal to a given number:

  Console.WriteLine(Math.Floor(3.9)); // Output: 3
  Console.WriteLine(Math.Floor(5.2)); // Output: 5
  Console.WriteLine(Math.Floor(7)); // Output: 7
  

• We can use this function if we want to compute the integral part of some division (quotient):

  int a = 3;
  int b = 7;
  
  Console.WriteLine(Math.Floor(20 / a)); // Output: 6
  Console.WriteLine(Math.Floor(b / a)); // Output: 2
  

Full lesson:

Remember how we first learn about the division of two integer numbers in primary school?

The quotient is the number of times a division is completed fully, while the remainder is the amount left that doesn't entirely go into the divisor.

Here are some examples:

10 / 2 = quotient 5, remainder 0
15 / 4 = quotient 3, remainder 3
20 / 3 = quotient 6, remainder 2

Floor division

Floor division (//) is a normal division operation except that it returns the integral part of the result (the quotient):

print(10 // 2) # Output: 5
print(15 // 4) # Output: 3
print(20 // 3) # Output: 6

It can also be used with variables:

a = 3
b = 7

print(20 // a) # Output: 6
print(b // a) # Output: 2

Modulo

The modulo operator (%) calculates the remainder of dividing two values:

print(10 % 2) # Output: 0
print(15 % 4) # Output: 3
print(20 % 3) # Output: 2

# Can be used with variables:
a = 2
b = 4

print(b % a) # Output: 0
print(11 % b) # Output: 3

Quotient and remainder

In programming, we combine both these concepts to get the quotient and remainder of some divison:

# Let's divide 26 by 3:
quotient = 26 // 3
remainder = 26 % 3

print(quotient) # Output: 8
print(remainder) # Output: 2

Assignment
Follow the Coding Tutorial and let's practice with quotient and remainder!

Hint
Look at the examples above if you get stuck.