Below are the functional units of computer. If you want to share your study material with others, you can drop us in our email

  • Arithmetic Logical Unit (ALU): ALU performs arithmetic and logic operations like Addition, subtraction, multiplication, division, logic and comparison. It is a part of the execution unit.
  • Control Unit (CU): Control unit controls the operations for all parts of the computer. It does not perform any data processing operations. It gives the command to transfer data from the input device into memory and from memory to ALU. It performs various functions:
    • Fetch-It gets an instruction from the main memory
    • Decode-Translates instructions into computer commands
    • Execute-It processes the commands
    • Store- It stores the result into the main memory


    Functions of this unit are:

  • Controls and transfers the data and instructions to the other parts of a computer.
  • It manages and coordinates all the units of the computer.
  • It obtains the instructions from the memory, interprets them and directs the operation of the computer.
  • It communicates with Input/output devices for transfer of data or results from storage.
  • It does not process or store data.
  • Central Processing Unit: CPU processes whatever input is entered into the computer. It is the part of the computer where the entire work is performed. It is also known as the brain of the computer. The ALU and the CU of a computer system are jointly known as the Central Processing Unit.

Machine cycle:

  • Fetch-In a machine cycle, instructions is fetched from the main memory.
  • Decode-The fetched instruction is translated into computer commands.
  • Execute-The command is actually processed.
  • Store-In this cycle, the result is written into the main memory.

Processor Speed- : Processor speed is measured in megahertz (Mhz) or in gigahertz. Processor speed is affected by system clock rate. The rate of an electronic pulse is used to synchronize processing.