Introduction to computer

ICS-XI-HBISE COMPUTER SCIENCE
SYEDA FARZANA SHAH (BS-IT, MBA-HRM) 1
TABLE OF CONTENTS
COMPUTER......................................................................................................................................................1
CHARACTERISTICS / FEATURES OF COMPUTER ................................................................................................1
COMPUTER DATA PROCESSING .......................................................................................................................2
HISTORY OF COMPUTERS: ...............................................................................................................................3
GENERATION OF COMPUTER:..........................................................................................................................4
CLASSIFICATION ACCORDING TO TYPE OF DATA HANDLED..............................................................................5
CLASSIFICATION ACCORDING TO PURPOSE......................................................................................................5
CLASSIFICATION ACCORDING TO SIZE..............................................................................................................6
COMPUTER SOFTWARE: ..................................................................................................................................7
SYSTEM SOFTWARE:........................................................................................................................................7
PROGRAMMING LANGUAGES..........................................................................................................................9
DATA COMMUNICATIONS / DATA PROCESSING BITS: ...................................................................................11
TYPES OF NETWORKS ....................................................................................................................................11
Chapter One
Introduction to Computer
Computer
A computer is an electronic device, operating under the control of instructions stored in its own memory that
can accept data (input), process the data according to specified rules, produce information (output), and store
the information for future use.
“A computer is an electronic machine that accepts information, stores it until the information is needed,
processes the information according to the instructions provided by the user, and finally returns the results
to the user. The computer can store and manipulate large quantities of data at very high speed, but a computer
cannot think. A computer makes decisions based on simple comparisons such as one number being larger
than another. Although the computer can help solve a tremendous variety of problems, it is simply a
machine. It cannot solve problems on its own”.
Characteristics / Features of computer
1: High speed: Computers have the ability to perform routine tasks at a greater speed than human beings.
They can perform millions of calculations in seconds.
2. Accuracy : Computers are used to perform tasks in a way that ensures accuracy.
3. Storage : Computers can store large amount of information. Any item of data or any instruction stored in
the memory can be retrieved by the computer at lightning speeds.
4. Automation : Computers can be instructed to perform complex tasks automatically ( which increases the
productivity).
5. Diligence : Computers can perform the same task repeatedly & with the same accuracy without getting
tired.
6. Versatility : Computers are flexible to perform both simple and complex tasks.
7. Cost effectiveness: Computers reduce the amount of paper work and human effort, thereby reducing costs.

Limitations of computers:
1. Computers need clear & complete instructions to perform a task accurately. If the instructions are not
clear & complete, the computer will not produce the required result.
2. Computers cannot think.
3. Computers cannot learn by experience.
Computer Data Processing
Data: It is the collection of raw facts, figures & symbols.
Information: It is the data that is processed & presented in an organized manner.
 Data is any collection of numbers, characters or other symbols that has been coded into a
format that can be input into a computer and processed.
 Data on its own has no meaning, or context.
 It is only after processing by a computer that data takes on a context and becomes
information.


 There are many types of data
 All data ends up being stored as a series of numbers inside the computer.
 Data can be input to the computer by the user in many different ways.
 The main types of data that can be input into a computer and processed are numeric, text,
dates, graphics and sound.
Input (Data):
Input is the raw information entered into a computer from the input devices. It is the collection of letters,
numbers, images etc.
Process:
Process is the operation of data as per given instruction. It is totally internal process of the computer
system.
Output (Information):
Output is the processed data given by computer after data processing. Output is also called as Result. We
can save these results in the storage devices for the future use.

HISTORY OF COMPUTERS: Since civilizations began, many of the advances made by science
and technology have depended upon the ability to process large amounts of data and perform complex
mathematical calculations. For thousands of years, mathematicians, scientists and businessmen have
searched for computing machines that could perform calculations and analyze data quickly and
efficiently. One such device was the abacus.
The abacus was an important counting machine in ancient Babylon, China, and throughout
Europe where it was used until the late middle ages. It was followed by a series of improvements in
mechanical counting machines that led up to the development of accurate mechanical adding
machines in the 1930’s. These machines used a complicated assortment of gears and levers to
perform the calculations but they were far to slow to be of much use to scientists. Also, a machine
capable of making simple decisions such as which number is larger was needed. A machine capable
of making decisions is called a computer.
The first computer like machine was the Mark I developed by a team from IBM and Harvard
University. It used mechanical telephone relays to store information and it processed data entered
on punch cards. This machine was not a true computer since it could not make decisions.
Dark Ages of Computer:
Middle Age of Computer:

Modern Ages of computer:
Generation of computer:
First Generation (1940-56):
The first generation computers used vacuum tubes & machine language was used for giving the
instructions. These computer were large in size & their programming was difficult task. The electricity
consumption was very high. Some computers of this generation are ENIAC, EDVAC, EDSAC &
UNIVAC-1.
Second Generation (1956-63):
In 2nd
generation computers, vacuum tubes were replaced by transistors. They required only 1/10 of power
required by tubes. This generation computers generated less heat & were reliable. The first operating
system developed in this generation.
The Third Generation (1964-71):
The 3rd
generation computers replaced transistors with Integrated circuit known as chip. From Small scale
integrated circuits which had 10 transistors per chip, technology developed to MSI circuits with 100
transistors per chip. These computers were smaller, faster & more reliable. High level languages invented
in this generation.

The fourth Generation (1972- 1990):
LSI & VLSI were used in this generation. As a result microprocessors came into existence. The computers
using this technology known to be Micro Computers. High capacity hard disk were invented. There is great
development in data communication.
The Fifth Generation (Present & Beyond):
Fifth generation computing devices, based on artificial intelligence, are still in development, though there
are some applications, such as voice recognition, that are being used today. The use of parallel processing
and superconductors is helping to make artificial intelligence a reality. Quantum computation and
molecular and nanotechnology will radically change the face of computers in years to come.
Classification of Computers
Classification According To Type of Data Handled
Analog computers
The term analog is taken from the word analogous which means similar. Analog computers are used to
measure continuous quantities. Analog computers are commonly used for scientific and engineering
problems, particularly in chemical industries, electric power plants, and petroleum refineries.
Examples of analog computers
Thermometer is an example of analog computer.
 It measures continuous variable (changeable) values.
 When we say that temperature raised from 22 C to 23 C. IS it the change direct? No. because in
between 22 and 23 there is a value 22.5, 22.25, 22.125 and so on.
 Traditional automatic watches are also example of analog computers
Digital Computers
Digital computers are computers that specialize in counting. Unlike the analog computer which receives
data in a continuous form, the digital computer handles values that are in a discrete (separate or distinct
0 form. Usually when we talk about computers they are digital computers (Desktop, laptop, notepad etc).
Hybrid Computers
 Hybrid means the combination of two things.
 Hybrid computers are the combination digital and analog.
 They have ability to measure continuous quantities like analog computers and represent the values
of measurements in digital form.
Example of Hybrid Computers
 Digital petrol pumps are the example of hybrid computers.
 They measure physical quantity and represent its values in digital form.
Classification According to Purpose
Special Purpose Computers and 2) General Purpose Computers

1. Special Purpose Computers: These are developed with a specific purpose. Some of the
areas where these computers are being used are – soil testing, drip irrigation, medical
scanning, traffic signals, spacecraft, rocket technology etc.,
2. General Purpose Computers: These are developed to meet the requirements of several
areas such as simulation, solving mathematical equations, payroll and personnel database.
Classification According To Size
a) Super Computers b) Mainframe Computers c) Mini Computers d) Micro Computers
a) Super Computers: An extremely fast computer that can perform hundreds of millions of instructions
per second. These have extremely large storage capacities and computing speeds which are at least
10 times faster than other computers. These are used for large scale numerical problems in scientific
and engineering disciplines such as electronics, weather forecasting etc. The first super computer
was developed in U.S.A. by CRAY computers.
b) Mainframe Computers: The large size computers including all peripherals and attached equipment
are termed as “Macro” and “Mainframe” computers.
A mainframe computer might support thousands of users, such as worldwide airline reservation
system. The mainframe used heavily in all kinds of business organization. They support a large
number of terminals for use by a variety of users simultaneously, but they are expensive and large in
size.
c) Mini Computers: A multi-user computer capable of supporting from 10 to hundreds of
simultaneously. It is a medium sized computer with moderate cost, available indigenously and used
for large volume applications. These computers are also found in laboratories for all types of
scientific and engineering work.
d) Micro Computers: A microcomputer is the smallest general purpose processing system. Micro
computers are also referred as ―personal computers (PC). These are self-contained units and usually
developed for use by one person at a time but can be linked to very large systems. They are cheap,
easy to use even at homes and can be read for variety of applications from small to medium range.
Types of Micro Computer
 Desktop Models
 Laptop Computers.
 Network Computers.
 Hand held personal computers of all types.
Table 1: Types of Computers
Type Physical Size Processing
Speed*
Number of Users
Microcomputer
or
Personal
Computer (PC)
Fits in hand, on lap, or
on desktop
Up to 400 MIPS One stand-alone or many may
access it through a network
Minicomputer Small cabinet; may fill
a small room with
accompanying
Up to 1000 MIPS Up to several hundred

peripherals
Mainframe Computer requires a
partial room; may
occupy several rooms
with accompanying
peripherals
Up to several
thousand MIPS
Hundreds to thousands
Supercomputer Entire room of
equipment
Up to 10,000
MIPS
Hundreds to thousands
COMPUTER SOFTWARE:
Program: Set of instructions that enables a computer to perform a given task.
The computer itself the hardware cannot do anything. The ingredient that enables a computer to perform a
specific task is software, which consists of electronic instructions. These instructions tell the machine’s
physical components what to do; without them, a computer could not do anything at all.
Software, simply are the computer programs. The instructions given to the computer in the form of a program
is called Software. Software is the set of programs, which are used for different purposes. All the programs
used in computer to perform specific task is called Software.
SYSTEM SOFTWARE:
System software is responsible for controlling, integrating, and managing the individual hardware
components of a computer system so that other software and the users of the system see it as a functional
unit without having to be concerned with the low-level details such as transferring data from memory to
disk, or rendering text onto a display. The program directly related to the hardware of computer and which
perform the fundamental task are termed as system software. A number of programs may be included in
system software but following are essential for any computer.
Language Translators/ processors
A Particular translator is required to execute any high level language program.
Each language has a different language translator, while the function of each translator is to convert high
level program into machine code.
Linkers
• These software manage different parts of any object program for a particular computer.
They create a link between the parts of program according to the specified memory.
• The linkers depend on the hardware of the computer.
• It is necessary for linking to know about the type of microprocessor, installed
amount of memory and other available resources of computer hardware. If a linker knows
all about hardware than it can create the best link for any object program.
Utilities
The main objective of utility programs is to give ease of work to the operator and increase the overall
efficiency of computer.
• Debuggers, defragmenters, memory mangers and virus detectors are utility programs.
Operating Systems
All the computer programs which are used to control and manage hardware and provide interface to
user to communicate with machine is called OS.

The Operating System tells the computer how to interact with user and how to use devices such as disk
drives, keyboard, and monitor.
Because operating system is necessary for controlling the computer’s most basic functions, it continues to
run until the computer is turned off.
 DOS, Windows XP, Windows Vista, Unix/Linux, MAC/OS X etc.
The components / Functions of operating system are:
• Process management
• Memory management
• Secondary storage management
• Input/output management
• Command interpreter
• Time sharing/ scheduling for tasks.
• Provide Security and integrity.
Types of Operating System Environment:
• Real-time Operating System: It is a multitasking operating system that aims at executing real-time
applications. Example of Use: e.g. control of nuclear power plants, oil refining, chemical processing and
traffic control systems, air
• Single User Systems: Provides a platform for only one user at a time. They are popularly associated with
Desk Top operating system which run on standalone systems where no user accounts are required.
Example: DOS.
• Multi User Systems: Provides regulated access for a number of users by maintaining a database of
known users. Refers to computer systems that support two or more simultaneous users. Another term for
multi-user is time sharing. Ex: All mainframes are multi-user systems. Example: Unix
• Multi-tasking and Single-tasking Operating Systems: When a single program is allowed to run at a
time, the system is grouped under the single-tasking system category, while in case the operating system
allows for execution of multiple tasks at a time, it is classified as a multitasking operating system.
• Distributed Operating System: An operating system that manages a group of independent computers
and makes them appear to be a single computer is known as a distributed operating system. Distributed
computations are carried out on more than one machine. When computers in a group work in cooperation,
they make a distributed system.
Commonly used operating system
UNIX: Pronounced yoo-niks, a popular multi-user, multitasking operating system developed at Bell Labs in
the early 1970s. UNIX was one of the first operating systems to be written in a high-level programming
language, namely C. This meant that it could be installed on virtually any computer for which a C compiler
existed.
LINUX: Pronounced lee-nucks or lih-nucks. A freely-distributable open source operating system that runs
on a number of hardware platforms. The Linux kernel was developed mainly by Linus Torvalds and it is
based on Unix. Because it’s free, and because it runs on many platforms, including PCs and Macintoshes,
Linux has become an extremely popular alternative to proprietary operating systems.

Windows: Microsoft Windows is a series of graphical interface operating systems developed, marketed, and
sold by Microsoft. Microsoft introduced an operating environment named Windows on November 20, 1985
as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Microsoft
Windows came to dominate the world’s personal computer market with over 90% market share, overtaking
Mac OS, which had been introduced in 1984.The most recent client version of Windows is Windows 10; the
most recent server version is Windows Server 2008 R2.
APPLICATION SOFTWARE:
Application software may consist of a single program, such as an image viewer; a small collection of
programs (often called a software package) that work closely together to accomplish a task, such as a
spreadsheet or text processing system; a larger collection (often called a software suite) of related but
independent programs and packages that have a common user interface or shared data format, such as
Microsoft Office, which consists of closely integrated word processor, spreadsheet, database, etc.; or a
software system, such as a database management system, which is a collection of fundamental programs that
may provide some service to a variety of other independent applications.
• Programs that help to accomplish specific task are referred application software.
• There are two types of application software. General and Special application softwares.
• Application software tells the computer how to accomplish tasks the user requires, such as creating
a document or editing a graphic image.
• Some important kinds of application software are:
Word processing programs Spreadsheet software
Database management Presentation programs
Graphics programs Networking software
Web design tools and browsers Internet applications
Communications programs Utilities
Entertainment and education Multimedia authoring
PROGRAMMING LANGUAGES
The Evolution of Programming Languages
To build programs, people use languages that are similar to human language. The results are translated into machine
code, which computers understand. Programming languages fall into three broad categories:
• Machine languages
• Assembly languages
• Higher-level languages
Machine languages Or First Generation Language 1GL:
 First-generation languages are the most basic type of computer languages, consisting of strings of numbers
(0s, 1s) the computer's hardware can use.
• Different types of hardware use different machine code.
• For example, IBM computers use different machine language than Apple computers.
Assembly Languages Or Second Generation Language 2GL:
• Assembly languages (second-generation languages) are only somewhat easier to work with than machine

languages.
• To create programs in assembly language, developers use cryptic English-like phrases to represent strings of
numbers. The code is then translated into object code, using a translator called an assembler.
Higher-Level Languages
Higher-level languages are more powerful than assembly language and allow the programmer to work in a more
English-like environment. Higher-level programming languages are divided into three "generations," each more
powerful than the last:
• Third-generation languages
• Fourth-generation languages
• Fifth-generation languages
Third-Generation Languages
• Third-generation languages (3GLs) are the first to use true English-like phrasing, making them easier to use
than previous languages.
• 3GLs are portable; meaning the object code created for one type of system can be translated for use on a
different type of system.
The following languages are 3GLs:
• FORTAN C
• COBOL C++
• BASIC Java
• Pascal ActiveX
Fourth-Generation Languages
• Fourth-generation languages (4GLs) are even easier to use than 3GLs.
• 4GLs may use a text-based environment (like a 3GL) or may allow the programmer to work in a visual
environment, using graphical tools known as object oriented programming. It also provide database
development concepts and tools.
The following languages are 4GLs:
• Visual Basic (VB)
• Oracle Database, SQL, FoxPro
• Authoring environments
Fifth-Generation Languages
• Fifth-generation languages (5GLs) are an issue of debate in the programming community – some programmers
cannot agree that they even exist.
• These high-level languages would use artificial intelligence to create software, making 5GLs extremely
difficult to develop.
LANGUAGE TRANSLATORS:
1. Interpreter
• These translators translate only one instruction at a time and execute it.

• After execution the translation is erased from memory and next instruction is loaded for translation.
• Therefore translation is required again if the program is executed again.
• It is a limitation of interpreters that it forgets translation after execution of instruction.
• A GWBASIC interpreter is required to run GWBASIC programs.
• Each programming language has its separate interpreter, if it is designed.
2. Compiler
• These translators are used to translate entire program at once and store their translated program on disk.
• The original program is called “Source Program” while its translated program is called “Object Program”.
• These translators cannot execute object program.
• The object program has to go through some other stages to be able to execute.
• Eg : C- Language
3. Assembler
• The assemblers are language translators for low level symbolic language programs.
• Assemblers can translates source program into object program.
• An assembler translates one source instruction into exact one machine code.
• The linking process is required on the object program to be able to execute it.
• Each low level symbolic language has its own assembler.
• Eg : Language
Data Communications / Data processing Bits:
 Data Communications is the transfer of data or information between a source and a receiver. The
source transmits the data and the receiver receives it. The actual generation of the information is not
part of Data Communications nor is the resulting action of the information at the receiver. Data
Communication is interested in the transfer of data, the method of transfer and the preservation of
the data during the transfer process.
MODEM (Modulator / Demodulator)
 A modem is a modulator/demodulator. It converts digital signals from a computer to analog signals
so they can be sent over a telephone line. The receiving computer will normally have a modem which
will convert the analog signals back to digital signals.
TYPES OF NETWORKS
LANs
 LANs (local area networks) are networks that connect computers and resources together in a building
or buildings close together.
 Local Area Networks - a system of computers that share resources such as hard-drives, printers, data,
CPU power, fax/modem, applications, etc... They usually have distributed processing - means that

there is many desktop computers distributed around the network and that there is no central processor
machine (mainframe). Can be campus wide like a college or university.
MANs
 Metropolitan Area Networks (MANs) are networks that connect LANs together within a city.
 Metropolitan Area Networks: a system of LANs connected through out a city or metropolitan. MANs
are used to connect to other LANs. A MAN has to have the requirement of using a telecommunication
media such as Voice Channels or Data Channels. Branch offices are connected to head offices
through MANs. Examples of companies that use MANs are universities and colleges, grocery chains
and banks.
WAN
 Wide Area Networks (WANs) connect LANs together between cities.
 Wide Area Networks: a network system connecting cities, countries, continents together.
TransCanada Pipeline has a WAN that stretches from Alberta to Boston. It goes from Alberta to
Ontario then through the States and ends up in Boston. The maintenance and control of the network
resides in Calgary. WANs are connected together using one of the telecommunications media.

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