Central Processing Unit Definition and Components

Tue, 02/02/2016 - 04:20 -- Umar Farooq

Central Processing Unit CPU is considered the brain of computer system. It is sometimes referred to processor or microprocessor. It has the responsibility to supervise the entire computer operations. This central processor execute the instructions made by users but also control primary and secondary storage of data and control functions of all attached devices. It receives instructions from hardware and software installed on the computer. The first microprocessor Intel 4004 was developed by Intel in 1971. It had 2,300 transistors and performed 60,000 operations / sec.


All the operations are controlled by the control unit taking instructions in the program stored in the memory unit. The athematic and logical unit, memory and control unit are called central processing unit.

Components of CPU

Thera are two main components of central processing unit.

Arithmetic Logical Unit

It is also known as ALU can performs digital and logical operations. Being a complex digital circuit performs mathematical and bitwise operations.  CUP arithmetic operation means calculation (plus, minus, multiplication and division) by requiring two numbers and produce a result.  Although every ALU must perform the two data words and the result, different processing and storage techniques are used in different models. The logical operations perform decision making by comparing two items. It compares two numbers by subtracting one number from another. After processing the information ALU send it to computer memory.

Control Unit

It controls and manage the different command by parts of the computer hardware. CU is the considered the brain command the body. For example, if you want to take a print, the control unit will make sure that the instructions are executed correctly. CU control and instruct the input, tells ALU to process, make necessary arrangement for primary and auxiliary storage and prepares output devices to execute. Following the sequence of excitation

  1. Take instruction from input devices like mouse, keyboard and scanner
  2. The instruction is transferred to instruction register and analyzed for execution
  3. Guides and send data to different computer areas for processing
  4. Make sure timely data processing
  5. Sends or receives signals for different parts of computer
  6. Handle multitasking, such as fetching, decoding and execution of command

Here I really want to say something about computer primary memory. it is also called magnetic core memory. it stores information it binary data and capable storing and recording information. Before any process take place it holds input data and results for execution after processing done.  Basically there are two functions of primary memory. First it stores active programs from operating system and secondly it stores data to be processed by ALU and the output results.