GCSE Computing — AQA/Computer structure/CPU (Central Processing Unit)

A computer can be divided into 4 major parts:

1. Input devices 2. Output devices 3. storage devices 4. CPU (which is the main brain of a computer. It does all the processing and calculations on inputs and provides outputs on screen)

There are two parts to the CPU:

The Arithmetic Logic Unit (ALU) performs arithmetic and logical operations. The Control Unit (CU) fetches and executes instructions stored in memory, calling on the ALU when necessary.

The CPU controls the entire system. It is basically what makes the computer work. A number of characteristics such as clock speed, cache size, and number of cores affect a CPU's performance. for example, a larger cache size (the cache is a small bit of ram stored on the CPU) will allow the CPU to randomly access more memory, increasing the computers performance. A CPU with multiple cores can run multiple instructions at the same time, increasing speed for programs. The clock speed is the rate at which the CPU can complete a processing cycle, measured in megahertz and gigahertz. A computer that can complete more processing cycles per second (larger clock speed) will be faster.