1. With a neat schematic block diagram of a digital computer describe its functional units

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Introduction to Computing

1. With a neat schematic block diagram of a digital computer describe its

functional units.
Central Processing Unit

Input Unit:-

  • The user can enter the data or program (instructions) to the computer

  • system.

  • It converts the data into a suitable form that can be understood by the

  • Computer.

  • The converted data is stored in the form of 0’s and 1’s and then sent to

  • Central processing unit

  • The user can also interact with other devices such as CPU, MU and

  • output unit.

Output unit:-

  • Accepts the result or data from memory which are in the form of 0’s and 1’s.

  • Output the results or data to a form which is suitable for human understanding.

Central Processing Unit;-

  • The data received from the input device is processed in this unit.

  • It consists of two functional units: 1. Arithmetic and Logic Unit (ALU)

2. Control Unit (CU)

1. Arithmetic and Logic Unit (ALU);-

  • An ALU consists of electronic circuitry which performs calculations with basic arithmetic operations such as addition (+), subtraction (-), multiplication (*), division (/).

  • It also consists of logic circuitry which performs logic operations like true or false, yes or no.

2. Control Unit (CU):-

  • The unit controls and co-ordinates all parts of computer system.

  • It executes an instruction by signaling to carry out the necessary data transfers and manipulations.

  • Identifies what action to be taken. (decoding)

Memory Unit (MU):-

This is the storage device where the data and instructions fed by the user are stored.

The computer memory is classified into

  • Main memory: This is the place where the data and instructions supplied by the input devices are stored.

This is the temporary memory because the data and instructions are erased

When the power goes off.

It consists of RAM and ROM main memories.

  • Secondary memory: This is the permanent memory and also called as back up memory.

It stores a large about of information for a long time.

  • Cache memory: This is the high speed memory and placed between the CPU and the main memory.

Users cannot access it.

2. Explain the different types of computers.
Digital Computer
Based on technology Analog Computer
Hybrid computer

Micro computer

Mini computer

Computers for Main frame computer


Super computer

l. Computers based on technology-

  • Digital computer:-Computers accept and process data in terms of digital data such as 0’s and 1’s

Series of 8 consecutive bits is called a byte

Series of bytes represent data or instruction

E.g. (Personal Digital Computer Assistant)

  • Analog computer:-They accept data whose values keep changing with respect to time.

Data may be in the form of continuous voltages, frequencies, temperature etc.

Processing is done on continuously varying signals.

E.g. Speedometer

  • Hybrid Computer:-It is designed to handle digital and analog computers and hence also called analog-digital computer.

Accepts analog signals and converts into digital form.
2. Computers for organization:-

  • Micro Computer:-It is powerful, easy maintenance, low cost, unporable.

It is the most common type of PC and commonly called as desktop.

They are small in size and do not have large storage capacities. The length of a microcomputer lines in the range 8-32 bits

E.g.: IBM PC, PS/2

  • Mini computer:-Computers with capabilities intermediate of that between main frame and micro computers. Hence called mid-range computers.

Word length is 32 bits

It is used by small and mid-size business organizations.

  • Main frame computer:-It is more powerful than micro computers and their word length size is 48,60 or 64 bits

They have high processing speeds and can store large amounts of data

They are used in research organizations, large industries, and large business and government organizations

They consume more electricity

E.g.: IBM 3000 series, UNIVAC 1180

  • Super computers:-Computers that are used for scientific and engineering applications.

Word length is 64-96 bit.

They can handle very large data bases or a great amount of data computation.

They can perform one trillion operations per second.

Used in the field of science and defense, designing and launching missiles, weather forecasting, biomedical research

Highest processing speed for at a given time.

E.g: CRAY-3, HITAC S-300

4. What are the different kinds of memory used in computers? Explain with examples.

Volatile memory-RAM

Primary memory

Non-volatile memory-ROM


Secondary memory
Cache memory
Primary memory:

  • The memory is accessible directly to the CPU of the computer.

  • The memory is very fast.

  • This allows the CPU to store and retrieve data quickly.

  • Volatile memory: The memory that loses its contents when the computer is turned off.

  • Since the CPU can read the data from the memory or can write the data into the memory they are also called as read-write memories.

  • E g. RAM (Random Access Memory): It is possible to read and write the data into the memory. It is temporary memory.

  • Non volatile memory: The memory that retains its contents even after the computer is turned off memory. They hold the data permanently.

  • E.g. ROM (Read Only Memory): The information stored in it can be only be read.

Secondary Memory:

  • Its is the permanent memory which stores large amount of information for a long time

  • It’s also called back up memory or auxiliary memory.

  • It is connected to CPU and is made of magnetic material.

  • E.g. Floppy disc, hard disc

Cache memory:

  • It’s a high speed memory and is placed between CPU and main memory.

  • The data and instructions stored in it are accessed at a higher speed

  • Users cannot access this memory

  • It stores data and instructions that are currently to be executed

5. Discuss the applications, merits and demerits of a computer.


  • Science:-Used by scientists to analyze large quantity of data to analyze the effect of earthquake on buildings and dams for satellite launching and remote controlling.

  • Education:-E-Learning is becoming popular. Computers are used as teaching aid in majority of educational institutions.

  • Medicine and Health:-Diagnosing the illness to monitoring the patient’s status till his complete recovery.

Using the computer generated images and results; they can pin-point the cause of

the disease

  • Engineering/Architecture/Manufacturing:-Engineers and architects use the computers for planning, designing and drawing the layouts for house, roads, dams etc.

  • Communication:-send and receive e-mails, e-shopping, e-banking, e-commerce, e-learning etc.

  • Business and banking:-For numerous administrative purposes, preparing salary bills

Used in banking, insurance sectors and marketing for online payments and

transactions, publishing etc.

Online business

  • Governments:-Used for weather forecasting, in military, satellite launching and controlling, communication, e-government etc.

For police force to search for the information on criminals, crime scenes, driving

licenses etc.

  • Entertainment:-Used in music industry, games etc.

Computer animation and colorful graphics with multimedia effect.

  • Speed:-The computers can process data at very high speed.

Speed is measured in terms in terms of MIPS and BIPS.

  • Accuracy:-The results produced by the computer are very accurate.

  • Reliability:-It gives correct and consistent result always even if they are used in adverse conditions.

  • Storage capability:-They can store large amounts of data and can be retrieved at any time in fraction of a second.

  • Versatility:-They can do variety of jobs based on the instructions given to them.

  • Diligence:-They can perform complicated work without any break for days together; even year together without committing any error.


  • Non-Intelligent:-It just performs the specified operations.

It does not think whenever it finds a command, instead it works accordingly.

It does not possess any intelligent for analyzing the problem.

  • Inactive:-If the power supply is stopped then the computer ceases to work.

6. What are editors, assembler, compilers, interpreters?





It allows the user to enter program and edit it

The process of converting assembly language instructions to machine readable form is carried out by a programmable assembler

It takes entire high level language program as input and translates it into machine language

It takes one statement of a high level language program as input and translates it into machine language and executes it.

Debugging is easy

Debugging is easy

Debugging is faster

Debugging is slow

E.g.: Turbo C

E.g,: TASM

E.g. TC computer


7. What are the 4 primary functions that an operating system performs?

a. Memory Management:-Allocating memory to the running program and reallocating when they are terminated

b. Processor Management:-Processing of jobs, deciding on the job scheduling technique and how a job to be processed longs.

Releasing the processor when the jobs are terminated.

c. Device Management:-Allocating the input and output devices to the running processes and reallocating them when processes are terminated.

d. File Mnagement: - Manging the file systems in terms of where the files are stored, their status and memory locations, opening and closing the files, providing access permission to the files.

E.g. of operating system are DOS, UNIX, WINDOWS NT, LINUX
8. Differentiate between WINDOWS and LINUX operating systems.



It is not free of cost

It is available free of cost

It supports GUI(Graphical User Interface)

It does not support GUI(Graphical User Interface)

Networking is possible

Networking is not possible

Requires very high configuration

High configuration is not required

Multi-media facility available

Multi-media support not available

Mobile computing is possible

Mobile computing is not possible

User friendly

Not user friendly

9. What is software? What are the different types of software?

Software is a set of programs which direct the various hardware components.

Application software

System software

Application software;-

  • It tells the computer how to accomplish specific tasks, such as word processing or drawing for the user.

  • Word processing software for creating text based documents

  • Spreadsheet for creating numeric based documents such as budgets

  • Database management software for building and manipulating large sets of data

  • Presentation program for creating and presenting electronic slide shows

  • Graphics program for designing illustrations or manipulating photographs, movies or animation

  • Web design tools and web browsers

  • Entertainment and education software

  • Games

System software:-

  • It is any program that controls the computer hardware or that can be used to maintain the computer in some way so that it runs more effectively

  • It has 3 basic types

-Operating system tells the computer how to use its own components.

It acts as an interrupt between the hardware application programs and the user

-A network operating system allows computer to communicate and share data across a network while controlling network operations and overseeing the network’s security

-A utility is a program that makes the computer system easier to use or perform highly specified functions

10. Brief history of computers


Invented by

Name of the computer


Charles Babbage

Analytical Engine- Father of computers


Lady Lovelace

Punch cards – Mother of computers

Augusta Ada King

First computer programmer


Konrad Zuse

General Purpose digital computer


John Atanasoff

Atanasoff- Berry computer (ABC)


Alan Turing and his team




Mark I


Von Neumann

Stored Program concept


Mauchly & Eckert


©Khalid Nazim S.A., King Saud University

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