Computer Systems and Organization Class 11 important notes

Computer Systems and Organizations is Unit 1 of CBSE Computer Science class 11. You can download
class 11 computer science chapter 1 pdf linked in this article.

Introduction to Computer Systems and Organization

In today’s life computers play a vital role in our day-to-day life. We are surrounded by computers nowadays. Most of our daily work is directly or indirectly connected with computer systems. Let’s discuss what is a computer system.

The computer systems and organization is a set of the following components:

Computer Components - Chapter 1 Computer Science Class 11

Hardware: Hardware is the tangible parts of computer systems such as a Keyboard, Mouse, Hard Disk, Motherboard, etc.
Software: Software is the programs stored in computers that help to do the user’s work and provide an interface to the user such as Microsoft PowerPoint, Excel, Adobe Reader, etc.

Functions of Computer Systems

Four main functions of Computer System

There are four main functions of the computer system:

  1. Input: The process of data feeding by the user (Data means raw facts and figures)
  2. Process: The actual work done in computers
  3. Output: The result of user’s task (It can be: On-screen (Soft Copy), On Paper (Hard Copy) or On Air)
  4. Storage: The process of saving data

Insights of Computer Systems and Organization

The computer system is just like an organization with different units. All units have their own functional parts or units to do a specific task.

Look at the following diagram:

Insights - Computer Systems and Organizations
Insights – Computer Systems and Organizations

CPU (Central Processing Unit)

It works like a manager of a company. It accepts a request from the Input unit, then guides, directs, controls, and governs the performance of the computer. It has three functional units:

1. CU (Control Unit) 2. ALU ( Arithmetic and Logic Unit) 3. Memory Unit

Functional Parts Of CPU

1. CU (Control Unit): It accepts the request from the CPU and does not perform any task itself. It determines, guides, and controls the request and then send it to ALU.

2. ALU (Arithmetic and Logic Unit): ALU accepts the request from CU and performs the required task. It checks the request for what kind of task to be performed such as arithmetic operation (Addition, Subtraction, Multiplication or Division) or Logical comparison such as (Less Than, Greater Than etc.). After completion of the task, it sends the request to the next unit.

3. MU (Memory Unit): It is the next functional unit of computer organization. It is responsible for storing data into computer storage locations. It stores data permanently or temporarily. Further MU is divided into two kinds of memory as follows:

Computer Systems and Organizations - Types of Memory

The memory is main part of Computer Systems and Organization.

Watch this video for more understanding:

Primary Memory

Primary memory is also known as the main memory. Primary memory is a space where users can open their files for work. It works just like a table or desk in our offices. It saves data temporarily. It is classified as into the following categories:

  1. RAM
  2. ROM
  3. Cache Memory

RAM (Random Access Memory)

Data can be accessed randomly. It is volatile memory i.e. when power gets off data will be lost.

ROM (Read Only Memory)

It plays an important role in performing POST(Power On Self Test). It will check all the connected devices are working properly or not. Data cannot be edited once written.

Computer Systems and Organizations - RAM and ROM

Cache Memory

It is used to increase the speed of operations of the CPU. It is placed between RAM and CPU. It stores copies of data from frequently accessed memory locations that reduce the average time required to access data. This memory is examined first when the CPU needs some data.

Secondary Memory Role in Computer Systems and Organization

Secondary memory is also known as auxiliary memory. It stores data permanently. It has a larger storage capacity than primary memory. Data written on secondary memory must be brought up onto primary memory before use.

Computer Systems and Organizations - Secondary Memory Storage Devices
Secondary Memory Storage Devices

Hard Disk

  • It has magnetic storage to store data, retrieve data
  • It has rotating platters coated with magnetic material
  • These platters are paired with magnetic heads
  • Magnetic heads are arranged on a moving actuator arm that read and write data to platter surfaces
  • It is a non-volatile memory
  • It has a large storage capacity compared to other secondary storage devices
Hard disk
Hard disk


IO and Battery are two devices which are performing the tasks of supplying input and output power in Computer Systems and Organizations.

  • It is pronounced as “eye-oh”
  • Refers to a program, operation or devices that transfer data to or from a computer and to or from a peripheral device
  • The transfer is input for one device and output for another device
  • Example: Writable CD
Computer Systems and Organization Class 11 important notes
IO Devices

Memory Units

Memory units helps to decide the capacity and requirements of storage in Computer Systems and Organization.

  • It is just like a cell; these cells are broken down into small units called bits
  • Bit means a binary digit either 0 or 1
  • 4 bits make up a nibble
  • 8 bits make up one byte
  • Every higher memory unit is equal to 210 of its lower units
Memory Units
Memory Unit Chart

Computer Systems and Organizations – Mobile System Organization

  • A Mobile is a portable computer in hand
  • It has a touch screen, call management system, front and rear camera, display system, memory like RAM as well as internal memory, SIM card, battery, speaker, and processor
  • A processor of the mobile system has less power compared to computer systems as they are running of small batteries
  • A mobile system has the following components:
    • CPU handles instructions
    • GPU assists the CPU to handle the visuals
    • Camera ISP (Image Signal Processor) provides and handles camera functions
    • Radio & 3G/4G Modem receives and transmits voice connections, 3G/4G enables the modem to send and receive digital signals
    • Memory the controller provides a direct link to memory
    • The battery system supplies power to the mobile

Computer Systems and Organizations – Software Concepts

As discussed earlier software is a program written in the programming language that allows doing specific tasks in computer. It is abbreviated as SW or S/W often. User needs to install them before use. There are two types of software:

  1. System Software
  2. Application Software

System Software

In Computer Systems and Organization, software plays vital role n operations. A computer is just like a rectangular box of hardware without software. The system software is responsible to perform some internal tasks of a computer system. There are two types of system software

Operating System

The primary function of the Operating System is to provide a platform to user and make the computer usable. It allows to make the hardware run competently. The tasks of the operating system are device management, process management, user management etc. There are different types of OS such as Single User OS, Multi-User OS, Time-sharing OS, Real-time OS, Multi-tasking OS, Distributed OS etc.

Language Processor

It is a translator that translates a high-level language program to machine level language. There are three types of language processors such as Assembler, Compiler and Interpreter.

Application Software

Application software carries out the important functions for Computer Systems and Organization with the help of programs. It provides special services or a specific task. This software is written by programmers to serve users as per their requirement. It is subdivided into categories such as Packages, Utilities, Customized Software, and Developer Tools.


The Packages are a special set of software that serves general-purpose Ex. MS Office, Adobe, DTP Software, Macromedia tools etc.


Utilities are helpful programs like basic editing, calculation, cleaning, rearranging, scanning files etc. Ex. Text Editor, Calc, Backup, Compression, Defragmenter etc.

Tailor-made software

Customized Software refers to tailor-made software that provides functions as per the requirement of people such as ERP software, Payroll Software, Hotel Management, Reservation System etc.

Developer Tools/IDE Tools

Developer tools are designed for the software developer to write code and compile, debugging, testing software Ex. Netbeans, Anaconda etc.

Watch this video for more understanding:

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Basic Computer Organizations and Software Concepts Class 11

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