The Arithmetic Logic Unit (ALU) — Computer Architecture | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 7% of your exam marks.

stable

Low

Stable7%

The fetch-decode-execute cycle and von Neumann architecture are tested almost every year.

The ALU carries out every arithmetic operation and every logical comparison required by the program.

Arithmetic operations include:

Addition, subtraction, multiplication, division
Increment (add 1), decrement (subtract 1)

Logical operations include:

Comparisons such as "is X greater than 5?", "is A equal to B?"
Bitwise operations such as AND, OR, NOT

A modern ALU can perform billions of these basic operations per second, and the result of each one is usually stored in the Accumulator register (covered in section 5).