Chapter -1 Computer System | CBSE class 11 Informatics Practices 2023

Computer System | CBSE class 11 Informatics Practices 2023

1. What is hardware?

Physical components of computer are known as hardware. Example, Keyboard, mouse, monitor etc.

2. What is software?

Software is a set of programs that can perform a particular task on computer. Example: MS Word, Excel, Paint etc.

3. Explain computer  system and its components.

Computer is an electronic device that can accept some input, processes it and produces some output.

Different Components of computer system are:

  1. Input Unit
  2. CPU
  3. Memory Unit
  4. Secondary Storage
  5. Output Unit

These components of computer system are diagrammatically represented as :

 

 

 

 

 

 

 

 

i. Input Unit

This unit is used to provide data and instructions to computer. It converts data and instructions into binary form which is understandable by the computer.

Most common examples of input devices are:

a. Keyboard: It is the most commonly used input device to type alphabets, digit and symbols.

b. Mouse: It is the most commonly used pointing device to move cursor and select different software components.

ii  Central Processing Unit (CPU)

It is called brain of the computer. It is responsible for carrying out all activities in a computer. It has three parts:

a. Control Unit  (CU): This unit controls flow of data and instructions between different units of computer. It decides whether data should go to ALU, registers, memory unit, secondary storage or output unit.

b. Arithmetic Logic  Unit (ALU): This unit is responsible  for arithmetic calculations and comparison.

c. Registers: These are memory cells inside CPU to store data temporarily. They are mainly used to store frequently used data.

iii. Memory Unit

Memory unit is also called primary memory.  This unit is used to store data and instructions in machine language i.e. in the form of 0 and 1.  It can be categorized into three parts:

  • RAM (Random Access Memory)
  • ROM (Read Only Memory)
  • Cache Memory

a. RAM (Random Access Memory)

It is used to store data and instructions temporarily. It stores data in it as long as the power is on. Contents of RAM are cleared when power supply is turned off . 

RAM is of two types:

Static RAM: It is made of flip-flops. It stores data in binary form. It is faster than dynamic RAM.

Dynamic RAM: It consists of capacitors and transistors. It uses electric charge to store the data.

b. ROM  (Read Only Memory)

ROM stands for Read Only Memory. It stores data permanently.  It contains instructions start up the computer and load operating system. 

ROM is of three types:

  • PROM (Programmable Read Only Memory) : It can be programmed once.
  • EPROM (Erasable Programmable Read Only Memory): It can be erased by keeping ROM chip under Ultraviolet light. It can be programmed more than once.
  • EEPROM (Electrically Erasable Read Only Memory): It can be erased by electrical signal. It can also be programmed more than once.

c. Cache Memory

It is high speed memory used to compensate the speed difference between CPU(very fast) and RAM(very slow). It stores the copies of  frequently used data from RAM. Hence it reduces the time required to access data from primary memory.

Measurement Units for Data
1 Bit = 0 or 1
1 Nibble= 4 Bits
1 Byte= 8 Bits
1 KB (Kilo Byte)= 1024 Bytes (210)
1 MB (Megabyte) = 1024 KB   (1024 X 1024 Bytes)
1 GB (Gigabyte) = 1024 MB
1 TB (Terabyte) = 1024 GB
1 PB (Petabyte) = 1024 TB
1 EB (Exabyte)  = 1024 PB
1 ZB (Zettabyte) = 1024 EB

4. Secondary Storage unit

This unit is used to store data permanently.  It consists of different types of storage devices. Most commonly used storage devices are:

a. Hard Disk : It is the most commonly used storage device to store data on a computer.  It consists of multiple magnetic plates and heads to read and write data. Magnetic plates are further divided into tracks and sectors to store data.

Maximum capacity of hard disk is 15TB.

b. Compact Disk (CD): CD is an optical disk to store data. CD’s have a storage capacity of 700 MB. There are three types of CDs:

i. CD-ROM (Compact Disk Read Only Memory): These are prerecorded CDs provided by manufacturers. Example: CDs containing softwares, games, eBooks etc.

ii. CD-R (Compact Disk Recordable): Data can be recorded on these CDs only once.

iii. CD-RW (Compact Disk Rewritable):These types  of CDs can be erased and recorded multiple times.

c. Digital Versatile Disk (DVD):

DVD is an optical disk to store data. DVD’s have a storage capacity of upto 17 GB. There are three types of DVDs:

i. DVD-ROM (Digital Versatile Disk – Read Only Memory): These are prerecorded DVDs provided by manufacturers. Example: DVDs containing movies etc.

ii. DVD-R (Digital Versatile Disk –  Recordable): Data can be recorded on these DVDs only once.

iii. DVD-RW (Digital Versatile Disk –  Rewritable):These types  of DVDs can be erased and recorded multiple times.

d. Blu Ray Disk:

Blu ray disk is optical disk that can store HD (High Definition) videos and data. They can store up-to 128 GB of data .

e. Pen Drive

It is also called Flash memory. It is a solid state memory that can store more than 128GB of data.

5. Output Unit

This unit is used to get output from computer. This unit convert machine language to human understandable form. Most commonly used output devices are:

a. Monitor: It is used to display data just like TV screen.

b. Printer: It can be used to take printout of data stored on computer.




4. Explain software and its types

Software is defined as a collection of programs  which are used for different purposes.

There are three types of software:

  • Application Software
  • System Software
  • Utility Software
  • Device Drivers

I. Application software:

Application software is used to perform specific operation on computer. They are of two types:

a. General Purpose software

These softwares can be used by more than one type of user. Example: MS Word is a general purpose software that can be used by students, teachers as well as clerks.

b. Special Purpose / Customized Software

These softwares can be used by only one type of user. Example: Banking Data Management software can be used only by bank employees.

II. System software:

System software is used to perform functions related to general operations of computer system.. They are of two types:

a. Operating System Software

It is an interface between user and computer. It takes instructions from user and further instructs hardware components to work. The results produced by hardware components are sent back to the user.

Example: Windows 10 , Unix, Linux, Android  etc.

b. Language Translators:

These softwares are used to convert the High Level Language instructions into Machine Language instructions.. They are of  three types:
i. Compiler: It converts High Level Language program into machine language in one go.

ii. Interpreter: It converts High Level Language program into machine language  line by line.
iii. Assembler: It converts assembly language into machine language.

III Utility Software

These softwares are used  to take backup, remove files, recover data and other tasks that assist in smooth operation of computer. Examples : Disk Defragmentation, Disk Clean, Backup, Anti-Virus etc.

IV Device Drivers

These softwares are necessary to run different types of hardware devices. For example, we need to install driver of a printer to make it work with a computer.



5. What is operating system? What are its functions?

Operating system is an interface  between computer hardware and user. It is responsible for the management of activities and the sharing of the computer resources.

Operating system has two parts

a. Kernel: It accepts instructions from shell and instructs hardware to perform specific operations.

b. Shell: It accepts instructions from user and instructs kernel to perform further operations

Different functions of operating System are:

  1. Process management:- Operating System can create and delete processes. It also provides mechanism for communication among processes.
  1. Memory management:- Operating System allocates and de-allocates memory to different softwares.
  2. File management:- It manages storage, retrieval, naming, sharing, and protection of files.
  3. Device Management: It is responsible allocation and de-allocation of the hardware devices to different programs.
  4. I/O System Management: It takes care of allocation and de-allocation of Input/Output devices to different programs.
  5. Secondary-Storage Management: Operating Systems takes care of primary as well as  secondary storage.
  6. Command interpretation: It interprets commands given by the user and further instructs hardware devices to perform operations according to the commands.
  7. Job accounting: It Keeps track of time & resource used by various programs and users.
  8. Communication management: It Coordinates the communication among different processes and  hardware resources.

6. What is System Bus? 

System bus is the collection of cables to interconnect major components of computer system. There are four types of buses:

  1. Data Bus: This bus is used to carry data from one part of computer to another.
  2. Control Bus: This bus is used to start or stop transfer of data.
  3. Address: This bus is used to specify address where data should be transferred.
  4. I/O Bus: This bus is used to provide communication with Input Output devices.

7. What is OSS (Open Source Software)? 

Open Source Software refers to that software whose source code is available. We can make changes to them as per our requirement and distribute them further. It may or may not be free of cost.

8. What is FLOSS? 

FLOSS refers to Free Libre and Open Source Software. This term is used to refer to a software that is free and whose source code is available.

9. What is Proprietary Software? 

Proprietary Software refers to that software which is neither open nor free. We need to pay a price for using such softwares. For example, Microsoft Windows, MS Office.

10. What is Freeware? 

Freeware is a software that is available free of cost. We can distribute it to others but can’t make any modifications to it.

11. What is Free Software? 

Free Software is a software that can be freely used, changed and distributed further. We don’t need to pay for these softwares.

Lesson tags: basic computer organization, brief introduction to functions of OS, central processing unit and its components, components of a computer system, components of a mobile phone, different functions of operating system, need for an operating system, types of cd, types of dvd, types of memory, types of software, types of storage devices
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