Components of a Computer System

Computer System

A computer system is a set of integrated devices that inputting , processing and outputting the storing data and information is known as computer system.

A computer is a programmable machine, which is designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and provides the required output after processing.

Computer components are divided into two major categories : hardware and software

computer hardware includes the physcal parts of the computer such as CUP, Memory monitor, keyboard and mouse etc.

Software are the set of programs that instruct the hardware for performing various functions.

Components of a Computer System

Computer hardware provides the physical mechanisms to  process, store, and input /output data. Includes CPU,  memory, I/O devices.

Software provides instructions to tell the hardware what  tasks to perform. It includes system and  application softwares.

Data in the computer may be representing numbers,  characters, graphics etc but is always kept in a form that  the hardware and software can understand and manipulate.

Input Unit

• Computer receives data and instructions  through the Input Unit.

• The input unit consists of one or more  input devices.

• Input devices include:

1. Keyboard
2. Mouse
3. Joystick
4. Scanner

Function of Input Unit

1. Accept the data and instructions from the  outside world.
2. Convert it to a form that the computer can  understand.
3. Supply the converted data to the computer  system for further processing.

Output Unit

• Computer provides information and results  of computation to the outside world  through the Output Unit.

• The output unit consists of one or more  output devices.

• Output devices include:

1. Monitor
2. Printer
3. Speaker

Function of Output Unit

1. Accept the results produced by the  computer. (These are in a coded form.)
2. Convert it to a form that the outside world  can understand. (OR, Converts it into  human readable form.)
3. Supply the converted results to the outside  world.

Central Processing Unit (CPU)

CUP is the brain of the computer

The ALU and the Control Unit (CU) of a  computer system are jointly known as the  central processing unit.

CUP= CU+ALU

CPU performs actual processing of data,  according to instructions from programs

Parts of the CPU

1. CONTROL UNIT  (CU)
2. Arithmetic Logic Unit (ALU)
3. Registers

Functions of CUP

1. It performs all calculations.
2. It takes all decisions.
3. It controls all units of the computer

Control Unit

• It controls all other units in the computer.

• It is the central nervous system of the  computer that controls and synchronizes its  working.

Functions of Control Unit

1. controls data movement and execution of  instructions(when to receive , where to store and when to display)
2. It instructs the input unit, where to store the data  after receiving it from the user and 
3. It controls the flow of data and instructions from the  storage unit to ALU.
4. It also controls the flow of results from the ALU to the  storage unit.
5. The control unit determines the sequence in which  computer programs and instructions are executed.
6. The control unit is also capable of shutting down the  computer when the power supply detects abnormal  conditions.

Arithmetic Logic Unit (ALU)

All calculations are performed in the  Arithmetic Logic Unit (ALU) of the computer.

•Whenever calculations are required, the  control unit transfers the data from memory  to ALU. Once the computations are done,  the results are transferred to the memory by  the control unit and then it is send to the  output unit for displaying results.

Arithmetic Operations

1. Addition
2. Subtraction
3. Multiplication
4. Division

Logical Operation

1. AND
2. OR
3. IF
4. ELSE
5. Greater Than (>)
6. Leass Than (>)
7. Greater Than or Equal (>=)
8. Less Than or Equal (<=)
9. Equal (=)
10. Not Equal (!=)

Function of Arithmetic Unit

1. It performs all arithmetic operations  (addition, subtraction, multiplication, and  division).
2. It performs all logic operations (Logic  operations test various conditions  encountered during processing and allow  for different actions to be taken based on  the results. )
3. It does comparison and takes decision.

Registers

Registers are small high speed storage  areas.

They hold various type of data, instruction, Address and the immediate result of the calculations when AlU performs arithmetic and  logical operation

To execute an instruction the control unit of the CPU retrieves it from main memory and place it into a register

Registers Type

1. Program counter
2. Memory address Register
3. Instruction Register
4. Memory buffer register
5. Memory data register
6. Accumulator

Program Counter(PC)

•To keep the track of the next instruction to be executed.

Instruction Register(IR)

•To hold instruction to be decoded by the control unit

Memory Address Register(MAR)

•To hold the address of the next location in the memory to be accessed

Memory Buffer Register(MBR)

•For storing data received from or sent to the CPU.

Memory Data Register(MDR)

•For storing operands and data

Accumulator(ACC)

•For storing the results produced by arithmetic and logic units.

Storage Unit

The storage unit of the computer holds  data and instructions(either temporarily or permanently) that are entered  through the input unit, before they are  processed

Function of Storage Unit

1. It received the data and instructions  required for processing from the input unit.
2. It stores the intermediate results.
3. It stores the final results before these  results are released to the output unit.
4. It saves data for later use.

Type of Memory

1. Primary Memory
2. Secondary Memory

Read More : Hierarchy of Memory