Topic 1.1 – Binary Systems

IGCSE Computer Science 0478

What is Binary?

Binary is a number system that uses only two digits: 0 and 1.

This is known as base-2, and it’s the core language that computers use to store and process information.

Why Do Computers Use Binary?

Computers are built on electronic circuits that recognize two states:

Because of this, binary is a natural and reliable fit for how digital systems operate.

Comparing Binary and Decimal

Feature Decimal (Base-10) Binary (Base-2)
Digits Used 0–9 0, 1
Place Values Powers of 10 Powers of 2
Example 245 = 2×100 + 4×10 + 5×1 1011 = 1×8 + 0×4 + 1×2 + 1×1 = 11

Converting Between Binary and Decimal

Binary → Decimal

Multiply each bit by its corresponding power of 2 (from right to left), and add the results.