Chapter 1 Computer System IP 11 | Important Notes Computer System

What is Computer System?

Combination of Software and Hardware together is called Computer System. A computer is a device (hardware) that can perform operations in accordance with a set of instructions called program (software).

Component of Computer System

Since a computer follows Input-Process-Output cycle, thus components of computer are categorized in three parts:

  1. Input Devices
  2. Central Processing Unit
  3. Output Devices

The basic component structure of computer is as shown below:

As shown in diagram various part of computer interact together to make the computer work, you input data to computer by using input devices and the CPU acts upon this data and provide output which is made available to user by using output device.

Input devices

Input device is responsible for taking input from user and provide to computer. Some most commonly used input devices are

  • Keyboard
  • Mouse
  • Microphone
  • Webcam
  • Scanner
  • Bar code reader
  • Light pen
  • Joystick

Output devices

Output device is responsible for providing and displaying output to user. Some most commonly used output devices are:

  • Monitor- LED Monitor, LCD Monitor, CRT Monitor
  • Printer- Impact Printer (Inkjet, Dot-Matrix), Non-Impact Printer (Laser, Inkjet)
  • Plotter
  • Speaker

CPU (Central Processing Unit)

CPU is control center of computer. It understands the instructions and carries out operations on the computer accordingly. It is the brain of computer and controls the activity performed by the computer.

The CPU has three components:

  • ALU (Arithmetic and Logical Unit)
  • MU (Memory Unit)
  • CU (Control Unit)

ALU (Arithmetic and Logical Unit)

ALU is component which is responsible for all the arithmetic or logical operation done on the data. Arithmetic operations are the basic mathematical calculations. Logical operations are basically comparison operation involves comparing data and determine different action to be performed PROCESSOR.

CU (Control Unit)

The control unit is a component which controls the flow of data and operations in a computer. It acts as a manager and instructs and coordinates all the components of CPU to perform their respective task.

MU (Memory Unit)

Memory unit is a component which is responsible for storing all data and information and instructions.

Memory of computer is more like a predefined working space where it temporary keep information and data to facilitate its performance. When the task is performed, it clears it’s memory and memory space is then available for the next task to be performed. This memory is often called main memory. There are two types of memory:

Primary Memory

Primary memory also known as Volatile memory that is temporary as it loses its contents when the computer’s power is turned off. It is internal memory that is accessed directly by the processor. Following are the Primary memory:

RAM: Random Access Memory is the memory that the computer uses for storing the programs and their data while working on them. We can either read data from the RAM or write onto it. Hence it is called read/write memory.

ROM: Read Only Memory is used to store the data about the hardware which does not required frequent updates, for example startup programs that loads Operating System into RAM. ROM is non-volatile memory. We can only read data from the ROM and hence called read only memory.

Cache Memory:  Catch memory is very high speed memory which is placed between processor and RAM to speed up the operations of CPU. Generally it stores the copies of data frequently accessed from RAM.

Secondary Memory

Secondary memory also known as non-volatile memory stores data and instructions permanently for future use. It is slower than primary memory but cannot be accessed by processor directly. Example of Secondary Memory are :

  • Hard Disk
  • CD/DVD
  • USB Flash Drive
  • Memory Card

Memory Unit

‘Byte’ is unit of memory used to measure amount of space consumed by data or instructions in memory.

Memory size conventions

1 Kilobyte = 1024 Bytes

1 Megabyte = 1024 KB

1 Gigabyte = 1024 MB

1 Terabyte = 1024GB

1 Petabyte = 1024TB

1 Exabyte = 1024 PB

Data Capturing

Data capturing refers to process of collecting or inputting data from different sources. To input data different input devices can be used such as keyboard, scanner, camera, bar code reader etc. data capturing might be a complex process due to nonuniformity in data. 

Data Storage

Data storage refers to process of storing captured data for future use. There are many different types of storage device are available which can be used to store data. Now a day due to rise in computers, Internet and Technology large volume of data being produced and hence the storage device should be of large capacity and updated regularly. to store large amount of data, Server can be deployed or Cloud computing can also be used.

Data Retrieval

Data Retrieval refers to accessing or fetching data from storage device as per requirement. Due to large volume of data now a day, system must have good quality and effective programs in order to access data at minimum time.

Data Deletion and Recovery

Deleting data refers to erasing data from storage device. There can be many reasons for deleting data such as system crash, accidental deletion, and illegal deletion by hackers/mischief mongers. When data is deleted from storage media, only the status (address entry) of data is changed and that space is shown empty to user without deleting data actually.

Data recovery is process of accessing deleted, lost or corrupted data from storage device. Deleted data can only be recovered when memory space of deleted data have not been overwritten with new data.


Software is set of programs that instruct hardware to what to and how to do. It makes hardware functional to achieve a common objective. Some example of software is Window10, Macintosh, MySQL, MS Word, Excel, Games etc.

Types of software

There are two types of software:

  • System software
  • Application software

System Software

System software manages computer system. It is software that control and coordinate all internal activities of a computer system.

System software can be categorized as

  • Operating System
  • Utility Software
  • Device Driver

Operating System

Operating System acts as an interface between user and machine. It is set of programs that –

  • Manages hardware resources
  • Manage memory
  • Display result in monitor
  • Control all hardware component attached to computer system
  • Read data through input devices

Examples of Operating System are Window10, Window8, Macintosh, Ubuntu, DOS etc.

Utility software

It is system software that helps you to configure and optimize and maintain a computer. Examples of utility software are- Disk Cleaner, File Backup Utility, Antivirus, Firewall, Disk Defragmenter etc.

Device Driver

Device driver is software which controls a particular type of hardware attached with a computer. It acts as an interpreter between particular hardware and computer system.

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