The central processing unit or CPU within any computer is where the actual computation occurs. As such, the CPU is a particularly key area of any computer system small or large.
The computer CPU contains all the arithmetic units and is able to provide the addition, subtraction and logical functions.
Central processing unit definition
It is sometimes useful to be able to define CPU and understand exactly what it is: its functions; boundaries; and its operation. In this way it is possible to understand which part of a computer the CPU is.
The central processing unit, CPU is sometimes referred to simply as the central processor, is defined as the primary component of a computer that processes instructions.
Another CPU definition is that the CPU is that part of a computer that performs logical and arithmetical operations on the data as specified in the instructions.
Computer CPU basics
Within a central processing unit there are typically two main units.
- Arithmetic logic unit, ALU: Within the central processing unit, the ALU performs arithmetic and logical operations.
- Control unit, CU: The Control Unit elements of the central processing unit extracts instructions from memory and decodes and executes them, and it uses the ALU where necessary.
CPU arithmetic logic unit, ALU
The arithmetic logic unit, ALU is one of the main functional blocks within a computer central processing unit.
The ALU performs all the processes related to arithmetic and logic operations that need to be done on instruction words.
In some microprocessors the ALU is subdivided into two further sections that are optimised for different functions:
- Arithmetic Unit, AU: This element of the central processing unit undertakes the purely arithmetic functions of adding, subtracting, etc.
- Logic Unit, LU: The logic unit within the central processing unit undertakes the logic or Boolean functions: AND; NAND; OR; NOR; IF, etc.
Even if these two entities are not separated out, the CPU will need to handle both functions.