Introduction to computers i

Introduction to Computer System
SWETA KUMARI BARNWAL 1
Computer
INTRODUCTION TO 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 use1.
Functionalities of a computer2
Any digital computer carries out five functions in gross terms:
Computer Components
Any kind of computers consists of HARDWARE AND SOFTWARE.
Hardware:
Computer hardware is the collection of physical elements that constitutes a computer system.
Computer hardware refers to the physical parts or components of a computer such as the monitor,
mouse, keyboard, computer data storage, hard drive disk (HDD), system unit (graphic cards, sound
cards, memory, motherboard and chips), etc. all of which are physical objects that can be touched.

Input Devices
Input device is any peripheral (piece of computer hardware equipment to provide data and control
signals to an information processing system such as a computer or other information appliance.
Input device Translate data from form that humans understand to one that the computercan work with.
Most common are keyboard and mouse
Example of Input Devices: -
1. Keyboard 2. Mouse (pointing device) 3. Microphone
4. Touch screen 5. Scanner 6. Webcam
7. Touchpads 8. MIDI keyboard 9. Electronic Whiteboard
10.Graphics Tablets 11.Cameras 12.Pen Input
13.Video Capture Hardware 14.Microphone 15.Trackballs
16.Barcode reader 17.Digital camera 18.Joystick
19.Gamepad
Note: The most common use keyboard is the QWERTY keyboard. Generally standard Keyboard
has 104 keys.
Central Processing Unit (CPU)
A CPU is brain of a computer. It is responsible for all functions and processes. Regarding
computing power, the CPU is the most important element of a computer system.
The CPU is comprised of three main parts :
* Arithmetic Logic Unit (ALU): Executes all arithmetic and logical operations. Arithmetic
calculations like as addition, subtraction, multiplication and division. Logical operation like
compare numbers, letters, or special characters
* Control Unit (CU): controls and co-ordinates computer components.
1. Read the code for the next instruction to be executed.
2. Increment the program counter so it points to the next instruction.

3. Read whatever data the instruction requires from cells in memory.
4. Provide the necessary data to an ALU or register.
5. If the instruction requires an ALU or specialized hardware to complete, instructthe hardware
to perform the requested operation.
* Registers :Stores the data that is to be executed next, "very fast storage area".
Primary Memory:-
1. RAM: Random Access Memory (RAM) is a memory scheme within the computer system
responsible for storing data on a temporary basis, so that it can be promptlyaccessed by the
processor as and when needed. It is volatile in nature, which meansthat data will be erased once
supply to the storage device is turned off. RAM storesdata randomly and the processor accesses
these data randomly from the RAM storage. RAM is considered "random access" because you
can access any memory cell directly if you know the row and column that intersect at that cell.
2. ROM (Read Only Memory): ROM is a permanent form of storage. ROM stays active
regardless of whether power supply to it is turned on or off. ROM devicesdo not allow data
stored on them to be modified.
Secondary Memory:-
Stores data and programs permanently :its retained after the power is turned off
1. Hard drive (HD): A hard disk is part of a unit, often called a "disk drive," "hard drive," or "hard
disk drive," that store and provides relatively quick access to large amounts of data on an
electromagnetically charged surface or set of surfaces.
2. Optical Disk: an optical disc drive (ODD) is a disk drive that uses laser light as part of the
process of reading or writing data to or from optical discs. Some drives can only read from discs,
but recent drives are commonly both readers and recorders, also called burners or writers.
Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read
and recorded by such drives. Optical drive is the generic name; drives are usually described as
"CD" "DVD", or "Bluray", followed by "drive", "writer", etc. There are three main types of
optical media: CD, DVD, and Blu-ray disc. CDs can store up to 700 megabytes (MB) of data and
DVDs can store up to 8.4 GB of data. Blu-ray discs, which are the newest type of optical media,
can store up to 50 GB of data. This storage capacity is a clear advantage over the floppy disk
storage media (a magnetic media), which only has a capacity of 1.44 MB.
3. Flash Disk: A storage module made of flash memory chips. A Flash disks have no mechanical
platters or accessarms, but the term "disk" is used because the data are accessed as if they were on a
hard drive. The disk storage structure is emulated.

Output devices
An output device is any piece of computer hardware equipment used to communicatethe results of
data processing carried out by an information processing system (such as a computer) which
converts the electronically generated information into human- readable form.
Example on Output Devices:
1. Monitor 2. LCD Projection Panels
3. Printers (all types) 4. Computer Output Microfilm (COM)
5. Plotters 6. Speaker(s)
7. Projector
Note Basic types of monitors are a.Cathode Ray Tube (CRT). B. Liquid Crystal Displays (LCD).
c.light-emitting diode (LED).
Printer types: 1-Laser Printer. 2-Ink Jet Printer. 3-Dot Matrix Printer

Software
Software is a generic term for organized collections of computer data and instructions, often broken
into two major categories: system software that provides the basic non- task-specific functions of
the computer, and application software which is used by users to accomplish specific tasks.
Software Types
A. 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. Generally, system
software consists of an operating system and some fundamental utilities such as disk
formatters, file managers, display managers, text editors, user authentication (login) and
management tools, and networking and device control software.
B. Application software is used to accomplish specific tasks other than just running the computer
system. 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 adatabase
management system, which is a collection of fundamental programs that may provide some
service to a variety of other independent applications.
Comparison Application Software and System
Software
System Software Application Software
Computer software, or just software is
a general term primarily used for
digitally stored data such as computer
programs and other kinds of
information read and written by
computers. App comes under
computer software though it has a
wide scope now.
Application software, also known as
an application or an "app", is
computer softwaredesigned to help
the user to perform specific tasks.
Example:
1) Microsoft Windows
2) Linux
3) Unix
4) Mac OSX
5) DOS
1) Opera (Web Browser)
2) Microsoft Word (Word Processing)
3) Microsoft Excel (Spreadsheet software)
4) MySQL (Database Software)
5) Microsoft PowerPoint (Presentation
Software)
6) Adobe Photoshop (Graphics Software)
Interaction:
Generally, users do not interact with
systemsoftware as it works in the
background.
Users always interact with application
softwarewhile doing different activities.
Dependency: System software can run independently
of the
application software.
Application software cannot run
without the
presence of the system software.

Unit of Measurements
Storage measurements: The basic unit used in computer data storage is called a bit (binary digit).
Computers use these little bits, which are composed of onesand zeros, to do things and
talk to other computers. All your files, for instance, are kept in the computer as binary
files and translated into words and pictures by the software (which is also ones and
zeros). This two number system, is called a “binary number system” since it has only
two numbers in it. The decimal number system in contrast has ten unique digits, zero
through nine.
Computer Storage units
Bit BIT 0 or 1
Kilobyte KB 1024 bytes
Megabyte MB 1024 kilobytes
Gigabyte GB 1024 megabytes
Terabyte TB 1024 gigabytes
Size example
• 1 bit - answer to an yes/no question
• 1 byte - a number from 0 to 255.
• 90 bytes: enough to store a typical line of text from a book.
• 4 KB: about one page of text.
• 120 KB: the text of a typical pocket book.
• 3 MB - a three minute song (128k bitrate)
• 650-900 MB - an CD-ROM
• 1 GB -114 minutes of uncompressed CD-quality audio at 1.4 Mbit/s
• 8-16 GB - size of a normal flash drive
Speed measurement: The speed of Central Processing Unit (CPU) is measured by Hertz (Hz),
Which represent a CPU cycle. The speed of CPU is known as Computer Speed.
CPU SPEED MEASURES
1 hertz or Hz 1 cycle per second
1 MHz 1 million cycles per second or 1000 Hz
1 GHz 1 billion cycles per second or 1000 MHz

Computers classification***
Computers can be generally classified by size and power as follows, though there is Considerable
overlap:
• Personal computer: A small, single-user computer based on a microprocessor. In addition to the
microprocessor, a personal computer has a keyboard for entering data, a monitor for
displaying information, and a storage device for saving data.
• workstation : A powerful, single-user computer. A workstation is like a personal computer, but it
has a more powerful microprocessor and a higher-quality monitor.
• minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users
simultaneously.
• mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands
of users simultaneously.
• supercomputer : An extremely fast computer that can perform hundreds of millions of instructions
per second.
Laptop and Smartphone Computers
LAPTOP: A laptop is a battery or AC-powered personal computer that can be easily carried and
used in a variety of locations. Many laptops are designed to have all of the
functionality of a desktop computer, whichmeans they can generally run the same
software and open the same types of files. However, some laptops, such as netbooks,
sacrifice some functionality in order to beeven more portable.
Netbook: A netbook is a type of laptop that is designed to be even more portable. Netbooks are
often cheaper than laptops or desktops. They are generally lesspowerful than other types
of computers, but they provide enough power for email and internet access, which is
where the name "netbook" comes from.
Mobile Device: A mobile device is basically any handheld computer. It is designed tobe extremely
portable, often fitting in the palm of your hand or in your pocket.Some mobile devices are
more powerful, and they allow you to do many of

the same things you can do with a desktop or laptop computer. These includetablet
computers, e-readers, and smartphones.
Tablet Computers: Like laptops, tablet computers are designed to be portable. However, they
provide a very different computing experience. The most obvious difference is that tablet
computers don't have keyboards or touchpads.Instead, the entire screen is touch-sensitive,
allowing you to type on a virtual keyboard and use your finger as a mouse pointer. Tablet
computers are mostlydesigned for consuming media, and they are optimized for tasks like
web browsing, watching videos, reading e-books, and playing games. For many people, a
"regular" computer like a desktop or laptop is still needed in order to use some programs.
However, the convenience of a tablet computer means that it may be ideal as a second
computer.
Smartphones: A smartphone is a powerful mobile phone that is designed to run a variety of
applications in addition to phone service. They are basically small tablet computers, and
they can be used for web browsing, watching videos, reading e-books, playing games and
more.
Data, Information and Knowledge
Data: Facts and figures which relay something specific, but which are not organized in any way and
which provide no further information regarding patterns, context, etc. So data means "unstructured
facts and figures that have the least impact on the typicalmanager."
Information: For data to become information, it must be contextualized, categorized,calculated and
condensed. Information thus paints a bigger picture; it is data with relevance and purpose. It may
convey a trend in the environment, or perhaps indicate a pattern of sales for a given period of time.
Essentially information is found "in answers to questions that begin with such words as who, what,
where, when, and howmany".
Knowledge: Knowledge is closely linked to doing and implies know-how and understanding. The
knowledge possessed by each individual is a product of his experience, and encompasses the norms
by which he evaluates new inputs from his surroundings.

The content of the human mind can be classified into four categories:
1. Data: symbols
2. Information: data that are processed to be useful; provides answers to "who", "what","where", and
"when" questions
3. Knowledge: application of data and information; answers "how" questions
4. Wisdom: evaluated understanding.
We need to understand that processing data produced Information and process Information
produces Knowledge and so on
Characteristics of Computer
Speed, accuracy, diligence, storage capability and versatility are some of the key characteristics of a
computer. A brief overview of these characteristics are
• Speed: The computer can process data very fast, at the rate of millions of instructions per second.
Some calculations that would have taken hours and days to complete otherwise, can be
completed in a few seconds using the computer. For example, calculation and generation
of salary slips of thousands of employees of an organization, weather forecasting that
requires analysis of a large amount of data related to temperature, pressure and humidity of
various places, etc.
• Accuracy: Computer provides a high degree of accuracy. For example, the computer can
accurately give the result of division of any two numbers up to 10 decimalplaces.
• Diligence: When used for a longer period of time, the computer does not get tired or fatigued. It
can perform long and complex calculations with the same speed andaccuracy from the start
till the end.
• Storage Capability: Large volumes of data and information can be stored in the computer and also
retrieved whenever required. A limited amount of data can be stored, temporarily, in the
primary memory. Secondary storage devices like floppy disk and compact disk can store a
large amount of data permanently.
• Versatility: Computer is versatile in nature. It can perform different types of tasks with the same
ease. At one moment you can use the computer to prepare a letterdocument and in the next
moment you may play music or print a document. Computers have several limitations too.
Computer can only perform tasks thatit has been programmed to do.

Computer cannot do any work without instructions from the user. It executes instructions as
specified by the user and does not take its own decisions.
Computer Viruses*
Viruses: A virus is a small piece of software that piggybacks on real programs. For example, a virus
might attach itself to a program such as a spreadsheet program. Each time the spreadsheet
program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other
programs) or wreak havoc.
•E-mail viruses: An e-mail virus travels as an attachment to e-mail messages, and usually replicates
itself by automatically mailing itself to dozens of people in the victim's e-mail address
book. Some e-mail viruses don't even require a double-click -- they launch when you
view the infected message in the preview pane of your e-mail software [source:
Johnson].
•Trojan horses: A Trojan horse is simply a computer program. The program claims to do one thing
(it may claim to be a game) but instead does damage when yourun it (it may erase your
hard disk). Trojan horses have no way to replicate automatically.
•Worms: A worm is a small piece of software that uses computer networks and security holes to
replicate itself. A copy of the worm scans the network for another machine that has a
specific security hole. It copies itself to the new machine using the security hole, and
then starts replicating from there, as well.
What are some tips to avoid viruses and lessen their impact?*
• Install anti-virus software from a reputable vendor. Update it and use itregularly.
• In addition to scanning for viruses on a regular basis, install an "on access" scanner
(included in most anti-virus software packages) and configure it to starteach time you start
up your computer. This will protect your system by checking for viruses each time you run
an executable file.
• Use a virus scan before you open any new programs or files that may contain executable
code. This includes packaged software that you buy from the store as well as any program
you might download from the Internet.
• If you are a member of an online community or chat room, be very careful about
accepting files or clicking links that you find or that people send you within the
community.
• Make sure you back up your data (documents, bookmark files, important email messages,
etc.) on disc so that in the event of a virus infection, you do not losevaluable work.
Types of Computer Language
Programming language
High-level programming language
Low-level programming language (Further divided in two parts)
1. Machine Language
2. Assembly Language
Types of Computer Language
Low-Level Languages: A language that corresponds directly to a specific machine
High-Level Languages: Any language that is independent of the machine
There are also other types of languages, which include

System languages: These are designed for low-level tasks, like memory and process
management
Scripting languages: These tend to be high-level and very powerful
Domain-specific languages: These are only used in very specific contexts
Visual languages: Languages that are not text-based
Esoteric languages: Languages that are jokes or are not intended for serious use
Language is a means of communication. Normally people interact with each other through
communication. On the same pattern, communication with computers is carried out through
a language. The language is understood both by the user and the machine. Normally every
language has its grammatical rules; similarly, every computer language is bound by rules
known as the SYNTAX of the language.
Programming language
A programming language is an artificial language that can be used to write programs that
control the behavior of a machine, particularly a computer.
Programming languages are defined by rules which describe their structure and meaning
respectively.
Many programming languages have some form of written specification of their syntax.
There are two levels of language.
1. High-level programming language
2. Low-level programming language
High-level programming language
These languages are normal, English like. Easy to understand statements to pass the
instruction to the computer. The languages are problem-oriented. It offers:
● Readability ● Easy Debugging ● Portability ● Easy software Development
Example: – BASIC, COBOL, FORTRAN, PASCAL, and C.
Low-level programming language
Low-level programming languages are sometimes divided into two categories:
1. Machine Language
Machine Language is the only language that is directly understood by the computer. It does
not need any translator program. We also call it machine code and it is written as strings of
1’s (one) and 0’s (zero). When this sequence of codes is fed to the computer, it recognizes
the codes and converts it into electrical signals needed to run it. For example, a program
instruction may look like this: 1011000111101. It is not an easy language for you to learn
because of its difficult to understand. It is efficient for the computer but very inefficient for
programmers. It is considered to the first-generation language. It is also difficult to debug the
program written in this language.
Advantages And Limitations of Machine Languages
Programs written in machine language can be executed very fast by the computer. This is
due to the fact that machine instructions are directly understood by the CPU and no
translation of the program is required. But writing a program in machine language has some
disadvantages which are given below:
1. Machine dependence: Since the Internal design of a computer varies from machine to
machine, the machine language is different from computer to computer. Thus a program
written in machine language in one computer needs modification for its execution on another
computer.
2. Difficult to the program: A machine language programmer must have thorough knowledge
about the hardware structure of the computer.

3. Error-prone: For writing programs in machine language, a programmer has to remember
the OPCODES and has to keep track of the storage locution of data and instructions. In the process, it
becomes very difficult for him to concentrate fully on the logic of the problem and
as a result, some errors may arise in programming.
3. Difficult to modify: It is very difficult to correct or modify machine language programs.
2. Assembly Language
It uses only letters and symbols. Programming is simpler and less time consuming than
machine language programming. It is easy to locate and correct errors in Assembly language.
It is also machine-dependent. The programmer must have knowledge of the machine on
which the program will run. An assembler is a program that translates an assembly language
program into a machine language program.
Assembly languages have the following advantages over machine languages;
1. Easier to understand and use: Assembly languages are easier to understand and use
because mnemonics are used instead of numeric op-codes and suitable names are used for
data.
2. Easy to locate and correct errors: While writing programs in assembly language, fewer
errors are made and those that are made arc easier to find and correct because of the use of
mnemonics and symbolic names.
3. Easier to modify: Assembly language programs are easier for people to modify than
machine language programs. This is mainly because they are easier to understand and hence
it is easier to locate, correct, and modifies instructions as and when desired.
4. No worry about addresses: The great advantage of assembly language is that it eliminates
worry about address for instructions and data.
Disadvantages
1. Machine Dependence: Programs written in assembly language are designed for the specific
make and model of the processor being used and are therefore machine-dependent.
2. Knowledge of hardware is required: Since assembly language is machine-dependent, the
programmer must be aware of a particular machine’s characteristics and requirements as the
program is written. Machine and assembly codes are based on the basic design of computers
and are referred to as ‘low-level language’.
Generation of Computers
Generation in computer terminology is a change in technology of computer is/was being used.
Initially, the generation term was used to distinguish between varying hardware technologies.
Nowadays, generation includes both hardware and software, which together make up an entire
computer system.
There are five computer generations known till date. Each generation has been discussed in detail
along with their time period and characteristics. In the following table, approximate dates against
each generation have been mentioned, which are normally accepted.

Following are the main five generations of computers.
1 G:
1. 1946-1959 is the period of first generation computer.
2. J.P.Eckert and J.W.Mauchy invented the first successful electronic computer
called ENIAC, ENIAC stands for “Electronic Numeric Integrated And
Calculator”.
Advantages:
1.It made use of vacuum tubes which are the only electronic component available
during those days.
2.These computers could calculate in milliseconds.
Disadvantages:
1. These were very big in size, weight was about 30 tones.
2. These computers were based on vacuum tubes.
3. These computers were very costly.
4. It could store only a small amount of information due to the presence of magnetic
drums.
5. As the invention of first generation computers involves vacuum tubes, so another
disadvantage of these computers was, vacuum tubes require a large cooling system.
6. Very less work efficiency.
7. Limited programming capabilities and punch cards were used to take inputs.
8. Large amount of energy consumption.
9. Not reliable and constant maintenance is required.
2G:
1. 1959-1965 is the period of second-generation computer.
2. .Second generation computers were based on Transistor instead of vacuum tubes.
Advantages:
Sr. No. Generation Year Technology Examples
1 First
Generation
1946-1959. Vacuum tube
based.
ENIAC, EDVAC, UNIVAC,
IBM-701, IBM-650
2 Second
Generation
1959-1965. Transistor based. Honeywell 400, IBM 7094,
CDC 1604, CDC 3600,
UNIVAC 1108
3 Third
Generation
1965-1971. Integrated Circuit
based.
PDP-8, PDP-11, ICL 2900,
IBM 360, IBM 370
4 Fourth
Generation
1971-1980. VLSI
microprocessor
based.
IBM 4341, DEC 10, STAR
1000, PUP 11
5 Fifth
Generation
1980-
onwards.
ULSI
microprocessor
based.
Desktop, Laptop, NoteBook,
UltraBook, Chromebook

1. Due to the presence of transistors instead of vacuum tubes, the size of electron
component decreased. This resulted in reducing the size of a computer as
compared to first generation computers.
2. Less energy and not produce as much heat as the first generation.
3. Assembly language and punch cards were used for input.
4. Low cost than first generation computers.
5. Better speed, calculate data in microseconds.
6. Better portability as compared to first generation
Disadvantages:
1. A cooling system was required.
2. Constant maintenance was required.
3. Only used for specific purposes.
3G:
1. 1965-1971 is the period of third generation computer.
2. These computers were based on Integrated circuits.
3. IC was invented by Robert Noyce and Jack Kilby In 1958-1959.
4. IC was a single component containing number of transistors.
Advantages:
1. These computers were cheaper as compared to second-generation computers.
2. They were fast and reliable.
3. Use of IC in the computer provides the small size of the computer.
4. IC not only reduce the size of the computer but it also improves the
performance of the computer as compared to previous computers.
5. This generation of computers has big storage capacity.
6. Instead of punch cards, mouse and keyboard are used for input.
7. They used an operating system for better resource management and used the
concept of time-sharing and multiple programming.
8. These computers reduce the computational time from microseconds to
nanoseconds.
Disadvantages:
1. IC chips are difficult to maintain.
2. The highly sophisticated technology required for the manufacturing of IC
chips.
3. Air conditioning is required.
4G:
1. 1971-1980 is the period of fourth generation computer.
2. This technology is based on Microprocessor.
3. A microprocessor is used in a computer for any logical and arithmetic function to
be performed in any program.
4. Graphics User Interface (GUI) technology was exploited to offer more comfort to
users.
Advantages:
1. Fastest in computation and size get reduced as compared to the previous
generation of computer.
2. Heat generated is negligible.
3. Small in size as compared to previous generation computers.
4. Less maintenance is required.

5. All types of high-level language can be used in this type of computers.
Disadvantages:
1. The Microprocessor design and fabrication are very complex.
2. Air conditioning is required in many cases due to the presence of ICs.
3. Advance technology is required to make the ICs.
5G:
1. The period of the fifth generation in 1980-onwards.
2. This generation is based on artificial intelligence.
3. The aim of the fifth generation is to make a device which could respond to natural
language input and are capable of learning and self-organization.
4. This generation is based on ULSI(Ultra Large Scale Integration) technology
resulting in the production of microprocessor chips having ten million electronic
component.
Advantages:
1. It is more reliable and works faster.
2. It is available in different sizes and unique features.
3. It provides computers with more user-friendly interfaces with multimedia features.
Disadvantages:
1. They need very low-level languages.
2. They may make the human brains dull and doomed.

Introduction to computers i

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