There are three main components to the CPU: the arithmetic-logic unit (ALU), control unit and on-board cache memory.

Control unit: The control unit is responsible for loading and interpreting the individual instructions that comprise the computer program. These instructions are in a language called machine code. Machine code is a pattern of ones and zeros. The control unit also has the task of getting the data needed by the instructions and returning the results of the processing after the instruction has been executed.

Arithmetic-logic unit: The ALU is responsible for carrying out arithmetic operations such as addition and subtraction as well as logical decisions such as whether one number is bigger than another. All programs consist of complex sets of arithmetic and logical operations. Another way of thinking of a logical operation is as a decision making operation.

On-board cache memory: Because the CPU can perform its operations much faster than data can be transferred from RAM, many CPUs have on-board cache memory. This is memory that the control unit can access very quickly and use for intermediate storage. Further, data and instructions can be loaded into cache before they are actually needed. When they are needed, the transfer is much faster than it would have been if RAM had been used.

Speed of the CPU: The CPU operates as a result of electronic pulses sent to it by another device on the motherboard called the clock. The speed of a CPU is measured by the maximum number of pulses it is able to handle. This is measured in MHz (megahertz) or millions of pulses per second or GHz (gigahertz) thousands of millions of pulses per second. A good personal computer will use a CPU with a clock speed of over 2 GHz. This means it receives 2 000 000 000 million pulses every second from the CPU.

Previously CPUs could only do one operation per pulse. With improvements in technology, they have been able to improve on this. For example, they can do one operation at the start of the pulse and one at the end of the pulse.