Computer Network
In connection with the information technology
and computers a network is a way to connect computers together so that they can
communicate, exchange information and pool resources or a network is a
communicating system connecting two or more computers. Network connects people
as close as the next office and as for as halfway around the world.
In business networks have revolutionized the use
of computer technology. Many businesses that used to relay on a centralized
system with mainframe and a collection of terminals now use computer networks
in which every employee who needs a computer has personal computer connected to
the network. In education, schools, colleges and universities have also shifted
to strategies built around networked personal computers.
Configurations or Topologies Networks
A network can be arranged or configured in
several different ways. This arrangements is called the network's topology. The
four principal network topologies are
1. Star Network
2. Bus Network
3. Ring Network
4. Hierarchical Network
1. Star Network
In a star network small computers or peripheral
devices are linked to a central unit. This central unit may be a host computer
or a file server. All the communications pass through this central unit.
Control is maintained by polling. Each device is in turn allowed to send the
message.
One particular advantage of the star form of
network is that it can be used to provide a time-sharing system. i.e several
users can share resources (time) on a central computer. The star is a common
arrangement for linking several microcomputers to a mainframe that allows
access to an organizations database.
2. Bus Network
In a bus network each device in the network
handles its own communication control. There is no host computer. All
communications control travel along a common connecting cable called a bus. As
the information passes along the bus it is examined by each device to see if
the information is intended for it.
The bus network is typically used when only a
few microcomputers are to be linked together. The bus network is not as
efficient as the star network for sharing common resources. However it is less
expensive and is in very common use.
3. Ring Network
In a ring network, each device is connected with
two other devices forming a ring. There is no central file server or computer.
Messages are passed around the ring until they reach correct destination. With
microcomputers ring network is the least frequently used arrangement. However it
is often used to link mainframes specially over wide geographical areas.
A ring network is useful in a decentralized
organization because it makes possible a distributed data processing system
i.e. computers can perform processing tasks at their own dispersed locations.
4. Hierarchical Network
This type of networks are also called hybrid
network. It consist of several computers linked to a central host computer just
like a star network. However these computers are also hosts to other smaller
computers or to peripheral devices. The host at the top of the hierarchical
network could be mainframe. The computers below the mainframe could be
minicomputers and those below microcomputers. This network allows various
computers to share database processing programs and different output devices.
It is useful in a centralized organizations.
Strategies of Networks
Every network has a strategy or a way of
coordinating the sharing of the information and resource. The most common
network strategies are terminal, peer-to-peer and client/server systems,
terminal network system. In this system processing power is centralized in one
large computer, usually the mainframe. The nodes (a node is any device
connected to network) connected to this host computer are terminals (a terminal
is a input or output device) with little or no processing capability. Most
airline reservation systems are terminal systems.
Peer-to-Peer Network System
In a peer-to-peer network, nodes can act both as
servers and clients. There are several advantages of using this type of
strategy. The networks as inexpensive and easy to install and they usually work
well for smaller systems with less than ten nodes. As the number of nodes
increases, however the performance of the network declines.
Client/Server Network System
Client/Server network system uses to coordinate
and supply services to all other nodes on the network. The server provides
access to centralized resources such as databases, applications software and
hardware. This strategy is based on specialization. Server nodes coordinate and
supply specialized services and client nodes request services.
One advantage of client/server network system is
its ability to handle very large networks efficiently. Another advantage is the
powerful management software that monitors and controls networks activities.
The major disadvantage of it is the high cost of installation and maintenance.
Advantages of Network
Networks provide tremendous benefits. The most
compelling advantages of network are as follows.
1. Networks allow users simultaneous access to
shared programs and data.
2. Network also allows users to share peripheral
devices such as printers and hard disks.
3. Network usually includes the capacity to send
e-mail and many e-mail systems let users to attach files to their messages.
4. Connecting computers to form a network makes
it easier to perform backups of the data on all the network hard disks.
Types of Networks
Communications differ in geographical size.
Three important types are LANs, MANs, WANs.
Local Area Networks (LANs)
Network with computers and peripherals devices
in close proximity within the same building are called local area networks
(LANs).
The figure shows an example of a LAN. This type
of arrangement has two benefits.
1. People can share different equipment, which
lowers the cos of equipment.
2. LAN also features a network gateway. i.e. a
LAN may be linked to other LANs or to large networks in this manner.
Metropolitan Area Network (MANs)
These network are used as links between office
buildings in a city. Cellular phone systems expand the flexibility of MANs by
allowing links to car phones and portable phones.
Wide Area Network (WANs)
Wide area networks are countrywide and worldwide
networks. Among other kinds of channels they use microwave relays and
satellites to reach users over long distances. One of the most widely used WANs
is Internet. Which allows users to connect to other users and facilities
worldwide.
Uses of Internet
The most common uses of Internet are
1. Communicating
Sending and receiving e-mail is the most popular
internet activity. You can send and receive e-mail to and from you friends and
family located almost anywhere in the world. You can join an listen to
discussions and debates on a wide variety of special interest topics.
2. Shopping
One of the fastest growing applications of
Interest is electronic commerce. You can visit a cyber mall for making
purchases.
3. Researching
Internet provides you to have one of the world's
largest libraries available from home.
4. Entertainment
Do you like music, the moves and reading or
playing computer games? You can find them all on Internet waiting for you to
locate and enjoy.
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Data Presentation
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The set of symbols to express quantities as the
basis of counting is referred to be a number system. There has been various
number systems under human use for the purpose of counting and measurement. For
instance decimal number system, octal number system, binary number system and
hexadecimal number system have been most popular number systems which human
beings have been utilizing for the purpose of counting and measurement.
Though a computer can process only binary
numbers i.e. only 0 and 1, we give a brief account of each of the number system
mentioned above. Inter conversion of these number systems would also be
discussed in this chapter.
Decimal Number System
This is the most commonly used number system and
which is very natural to man, hence very easy to use and remember. It consists
of ten digits, i.e. from 0 to 9. As the total number of digits used in a number
system is called its base or radix, hence base of radix of decimal number
system is said to be ten.
Binary Number System
The base or radix of binary number is two,
implying that there are only two digits 0 and 1 used in binary number system.
This number system has become most popular system because of its use by the
computers for processing data.
Octal Number System
This number system is consist of eight i.e.
0,1,2,3,4,5,6 and 7. Hence the base or the radix of octal number system is
eight. Actually this number is a short hand version of binary numbers, Hence
one octal represents three binary digits.
Hexadecimal Number System
Hexadecimal numbers are extensively used in
microcomputers. As they are much shorter than binary numbers, hence easy to
write and remember. They are also a short hand version of binary numbers. The
hexadecimal also called Hex is equivalent to four binary digits. This number
system consists of 0,1,2,3,4,5,6,7,8,9, A,B,C,D,E and F. The base of this
number system is 16. The symbol A........F stand respectively for 10.....15.
Binary to Decimal Conversion
All the number system may be easily converted
into other number systems. In order to convert binary numbers into decimal
numbers we multiply each bit of a particular binary number with (n-1) power of
2.
Add all the resultant multiplied bits.
Example No. 1
To convert the binary number 10010 to a decimal
number we proceed as follows:
100102 = (1 x 24) + (1 x 23) + (1 x 22) + (1 x
21) + (1 x 20)
= (1 x 16) + (0 x 8) + (0 x 4) + (1 x 2) + (0 x
1)
= 16 + 0 + 2 + 0
= 18
It should be kept in the mind that any number
raised to the power 0 equals 1.
Example No. 2
Similarly in order to convert the binary number
110111 to a decimal number we may proceed as follows:
1101112 = (1 x 25) + (1 x 24) + (1 x 23) + (1 x
22) + (1 x 21) + (1 x 20)
= (1 x 32) + (1 x 16) + (1 x 8) + (1 x 4) + (1 x
2) + (1 x 1)
= 32 + 16 + 0 + 0 + 4 + 2 + 1
= 56
Example No. 3
If there is a period (.) in the binary number
e.g. (1011.10). Then the conversion of such binary number can be illustrated as
follows:
(10112) = (1 x 23) + (1 x 22) + (1 x 21) + (1 x
20)
= (1 x 8) + (0 x 4) + (1 x 2) + (1 x 1)
= 8 + 0 + 2 + 1
= 11
AND
(.102) = (1 x 2-4) + (1 x 2-2)
= (1 x 1/2) + (1 x 1/4)
= 1/2 + 0 = 0.5
Hence (1011.102) = 11.5
Decimal to Binary Conversion
A decimal number can easily be converted to a
binary number. For this purpose we take following steps.
1. Divide the decimal number by 2 and note down
the remainder.
2. Take the quotient and again divide by 2, then
note down the remainder again.
3. Repeat the 2nd step unit you get 1 as the
quotient.
4. The remainders in the reverse order would be
our required binary number.
Example No. 4
For example in order to convert decimal number
15 to binary number. we may proceed as follows.
15/2 = 7 and the remainder is 1
7/2 = 3 and the remainder is 1
3/2 = 1 and the remainder is 1
1/2 = 0 and the remainder is 1
Hence the required binary number is 1111
Converting Decimal Fractions to Binary Numbers
The most simple method of converting fractional
decimal numbers to binary number is repeated multiplication by two. In this
method numbers to the right of the decimal point are repeatedly multiplied by 2
till we get a whole number. The product in fractions is assigned as 0 bit while
in whole number it is assigned as 1 bit.
The process of converting a fractional decimal
number to binary number would be explained by the following example.
Example No. 5
Let us suppose the we want to convert 0.125 in a
binary numbers then proceed as follow.
0.125 x 2 = 0.250 it carries 0
0.250 x 2 = 0.500 it carries 0
0.500 x 2 = 1.00 it carries 1
Hence we can conclude that (0.125)10 = (0.001)2
Addition to Binary Numbers
In order to add binary number below given table
should be kept in mind
0 + 0 = 0
0 + 1 + 1
1 = 0 = 1
1 + 1 = 0 with a carry of 1
The following example will illustrate the
addition of binary numbers.
Example No.6
Add 1001 and 1010
1001 + 1010 = 11011
Subtraction of Binary Numbers
In order to subtract a binary number from
another binary number you must keep the following table in your mind.
0 - 0 = 0
1 - 0 = 1
1 - 1 = 0
0 - 1 = 1 with a barrow of 1
The process of binary subtraction an be
illustrated with the help of example given below
Example No. 7
For subtracting binary number 101 from 1001 we
proceed as follows
1001 - 100.1 = 1.11
Octal to Decimal Conversion
For converting an octal number to a decimal
number we use the same sort of polynomial as was used in the binary case.
However in octal to decimal conversion the base or radix is 8 instead of 2.
The process of converting an octal number into a
decimal number would be clarified with the help of following example.
Example No. 9
The Octal number 2134 can be converted into
decimal number by proceeding as follows
(2134)8 = (2 x 83) + (2 x 82) + (2 x 81) + (2 x
80)
= (2 x 512) + (1 x 64) + (3 x 8) + (4 x 1)
= 1024 + 64 + 24 + 4
= 1116
Hence (2134)8 = (1116)10
Example No. 10
The octal number 1.123 can be converted to
decimal number as follows
(1.123)8 = (1 x 80) + (1 x 8-1) + (1 x 8-2) + (1
x 8-3)
= (1 x 1) + (1 x 1/8) + (1 x 1/64) + (3 x 1/512)
= 1 + 1/8 + 2/64 + 3/512
= 1 83/512
Decimal to Octal Conversion
For converting decimal number to octal number.
we apply a method of repeatedly dividing decimal by 8 and use each reminder as
a digit in the octal number. The process of converting decimal to octal number
may be illustrated by the following example.
Example No. 11
To convert the decimal number 429 to octal
number we process as follows
429/8 = 53 Reminder is 5
53/8 = 6 Reminder is 5
6/8 = 0 Reminder is 6
Hence (429)8 = (655)10
Octal to Binary Conversion
As we have mentioned earlier that octal number
system is a short hand version of binary numbers and one octal represents three
binary digits as shown by the following table
Equivalent Octal and Binary Number
Octal 0
1
2
3
4
5
6
7
Binary
000
001
010
011
100
101
110
111
In order to convert an octal number to a binary
number we just replace each octal digit with the appropriate three bits. This
produce an be explained with the help of following example
Example No. 12
(25)8 = (010101)2
Because (2)8 = (010)2 and (5)8 = (101)2 as shown
by the above table.
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Computer
Software and Programming Languages
Friendsmania.net
An information system has five parts. People,
procedures, software, hardware and data. Software which is one of the most
important part of an information system. Is an other name for a program or
programs. Program is the step by step instructions that tell the computer how
to do its work. The purpose of a software is to convert data (unprocessed
facts) into information (processed facts). In most cases, words software and programs
and interchangeable.
There are two major kinds of
software-application software and system software.
Application software are the software the users
of the computer use. Whereas system software are used by the computers.
Application Software
Application software may be describe as end-user
software. They perform useful work on general-purpose tasks such as word
processing and cost estimating.
Application software may be
1. Packaged
2. Custom Made
1. Packaged Software
Packaged Software are the programs prewritten by
professional programmers that are typically offered for sale.
2. Custom-Made Software
Custom-Made or Custom programs are the programs
written for a specific purpose and for a specific organization. Using computer
languages, programmers create this software to instruct the company's computer
to perform whatever tasks the organization wants.
There are certain general purpose programs which
are called "basic applications" The most popular basic tools are
Word Processing Programs used to prepare written
document.
Spreadsheets Programs used to analyse and
summarize numerical data.
Database Manageers used to organize and manage
data and information.
Presentation Graphic Programswhich are used to
communicate a message.
Personal Information Management Programs used to
organize and schedule activities.
Integrate Programs which combine some or all of
these applications in one program.
Summary of Basic Application Software
The summary of the basic application software
mentioned above has been given below. Which shows various software designed by
well known software publishers. Microsoft, Lotus and Corel.
Basic Applications
Word Processors = Microsoft Word, Lotus, Word
Pro, Corel WordPerfect
Spreadsheets = Microsoft Excel, Corel Quattro
Pro, Lotus-2-3
Database Managers = Microsoft Access, Corel
Paradox, Lotus Approach
Presentation Graphics = Microsoft PowerPoint,
Corel Presentation
Personal Information managers Microsoft Outlook,
Lotus Organizer
Integrated Packages = Microsoft Work, Lotus
Works.
Software Suites = Microsoft Office 97, Corel
Office 97
Common Features of Basic Application
As all the above mentioned categories of
software are designed to be used by many people to perform most common kinds of
tasks we call them basic applications. Most common application software have
some common features. The most important of them are given below.
Menu
Almost all software packages have menus to
present commands. Typically menus displayed in a menu bar at the top of the
screen when one of the item is selected a pull down menu appears.
This is a list of commands associated with the
selected menu.
Shortcut keys
Many applications also have shortcut keys for
frequently used commands. Many of the shortcut keys are function keys. F1, F2
and so on. Others shortcut use key combinations typically consisting of the
Alt, Ctrl or Shift key used in combination with a letter number or function
key. For example in Word97 the short cut key F7 starts the spelling tools and
the key combinations of shift and F7 starts the Thesaurus tools.
Toolbars
Toolbars are typically below the menu bar. They
contain icons or graphic representations for commonly for commonly used
commands.
Help
For most applications packages one of the menus
on the menu bar is Help. This typically include a table of contents a search
feature to locate reference information about specific commands and access to
specific learning features such as tutorials and step-by-step instructions.
Dialog Boxes
Dialog boxes frequently appear after selecting a
command from a pull down menu. These boxes are used to specify additional
options.
Scroll Bars
Scroll bars are usually located on the right and
/ or the bottom of the screen. They enable user to display additional information
not currently visible on the screen.
Edit
The ability to change or edit entries is a
feature common to almost all applications. The edit feature makes revising and
updating easy and is one of the most valuable features.
Save and Print
Common to all applications software is the
ability to save or store your work as a file on a floppy or hard disk. This
allows user to open and use the file at a later time in case user wants to add
or modify the document. In addition all applications allow user to a copy of
his document on paper.
Word processing programs and spreadsheets
program are most commonly used categories of application software hence we
explain them in much more detail.
Word Processors
word processing software creates text-based documents
such as letter, memos, term papers and reports. Once it was thought that only
secretaries would use word processors. Now they are used extensively in
managerial and professional life. Indeed, it has been found that among the
basic software applications. Word processors are most important software used
by common people.
Popular word processing packages include
Microsoft Word. Corel WordPerfect and Lotus Word Pro as shown in the above
summary of basic applications.
Important Features of Word Processors
Some important features shared by most word
processors are as follows
Word Wrap and the Enter Key
One basic word processing feature is word wrap
i.e. word processor automatically moves the insertion point to the next line
once the current line is full. The begin a new paragraph or to leave a blank
line Enter key is pressed.
Spelling and Grammar Checkers
Many word processors include a spelling checker
feature that identifies typing errors. For example Word97 identifies misspelled
words with a red wavy underline. Similarly grammar checkers can be run that
will identify poor wording excessively long sentences and incorrect grammar.
Alignment
Text can be aligned within the margin in various
way. The most common alignment is left alignment.
Formatting
Text can be enhanced in a variety of ways
including adding basics formatting such as bold, under line and italics.
Besides above mentioned feature other common
features of word processors are References, Search and Replace, Tables,
Hyperlinks, Thesaurus, Graphics, Internet publishing and Workgroup.
Spreadsheets
Spreadsheets is an electronic worksheet used to
organize and manipulate and display option for "what-if" analysis.
Spreadsheets are used by financial analysts, accountants, contractors and other
concerned with manipulating numeric data.
Popular spreadsheets packages include Microsoft
Excel, Quattro Pro and Lotus 1-2-3 as shown by above summary.
Common feature of Spreadsheets
Like the word processors, spreadsheets designed
by various software publishers share following common features.
Formulas and Functions
Formulas are the instructions for calculations.
They calculate result using the numbers in reference cells. Whereas functions
are prewritten formulas that perform calculations automatically.
Analysis
The recalculation feature can be used to analyze
the effect of changes to the spreadsheets.
Analytical Graphs
To help visualize the data in spreadsheets user
can create analytical graphs or charts.
Workgroup
One of the newest additions to spreadsheets
applications is the workgroup program which allows multiple users to
collaborate electromically on spreadsheet.
Linked Files
Most spreadsheets programs allow users to link
cells in one worksheet file to cells in other worksheets in the same file or to
other worksheet files. Whenever a charge occurs in one file the linked cells in
the other worksheets are automatically updated.
Advanced Application Programs
Besides above mentioned basic application
programs there are certain programs which are called "advanced
applications". These are more specialized than the basic application.
These programs are widely used in certain career areas. The most popular tools
are:
Graphic Programs used to create professional
publications and to capture and edit graphic images.
Multimedia used to integrate all kinds of
information including video, audio, graphic and text into a single interactive
presentation.
Web Publishers used to create interactive
multimedia web page. Project management used to plan projects schedule people
and control resources.
System Software
The user interact with the application software
whereas system software enables the application software to interact with the
computer hardware. System software is a "background" software. It
includes programs that help the computer manage its internal resources.
Kinds of System Software
System software deals with the physical
complexities of how the hardware works. System software consists of the
following four programs.
1. Bootstrap loader
2. Diagnostic routines
3. Basic input-output system
4. Operating System
1. Bootstrap loader
The bootstrap loader is a program that is stored
permanently in the computer's electronic circuitry. When computer is turned on
the bootstrap loader obtains the operating system from hard disk and loads it
into memory. This is called booting the system.
2.Diagnostic Routines
These are also programs stored in the computer's
electronic circuitry. They start up when machine is turned on. They test the
primary memory the central processing unit and other parts of the computer.
Their purpose is to make sure the computer is running properly.
3. Basic Input-Output System
It consists of service programs stored in
primary storage. These programs enable the computer to interpret keyboard
characters and transmit them to monitor or to a floppy disk.
Operating System
The operating system is a collection of programs
that help the computer to manage its resources. The Operating System takes care
of lot of internal matters. For example it interprets the commands user gives
to run programs. It manages memory data and file.
The most important system program is the
operating system which interacts between the application software and the
computer. The operating system handles such details as running (executing)
programs, storing data and programs and processing data.
Microcomputer operating systems change as the
machines themselves become more powerful and outgrow the older operating
systems.
The most popular microcomputer operating systems
are
DOS the original operating system for
International Business Machines (IBM) and IBM compatible microcomputers.
Windows not an operating system but an
environment that extends the capability of DOS.
Windows 95 a widely used operating system with
the built-in internet support.
Windows 98 a new operating system with the
intensive internet and multimedia support.
Windows NT a powerful operating system designed
for powerful microcomputers.
OS/2 Warp the operating system developed by IBM
for powerful microcomputers.
Macintosh Operating System the standard
operating system for Apple Corporation's Macintosh computers.
Unix an operating system originally developed
for microcomputers that can run on many of the powerful microcomputers.
Disk Operating System
DOS's original developer Microsoft Corporation
sells it under the name MS-DOS. It was originally standard operating system for
all microcomputers which were IBM compatible or DOS based.
Advantages
1. Even today DOS is still widely used operating
system.
2. An enormous number of application programs
have been written for DOS. Indeed more specialized software is available for
DOS for than any other operating system.
3. DOS runs on many computers, old and new that
are cheap.
Disadvantages
1. It can support very limited primary storage.
2. It can be used only for single-tasking and
not for multi-tasking.
3. It uses character-based interface.
Windows 98
Windows like Windows 95, Window 98 and Windows
NT is not a operating system, rather an operating environment. While Windows
95, Windows 98 and Window NT are operating systems. But Windows 98 is one of
the most popular operating systems being used nowadays. It is an advanced
version, designed for today's very powerful microcomputers.
Advantages
1. It is faster in many common tasks like
starting up loading applications and shutting down. It includes a Tune-up
wizard automatically monitors system operation and suggest ways to improve
performance.
2. Windows 98 is fully integrated with
Microsoft's browser, Internet Explorer, making Internet access easier and
faster.
3. Plug and play capability is extended to
support the newest advance in technology. Multiple views of an application or
multiple applications can be viewed on separate monitors simultaneously.
4. Windows 98 has advanced audio and video
capability. With a tuner card, TV on microcomputers monitor can be watched.
Government Jobs
Pakistan, Bank Jobs, Government Sector jobs, Private jobs, Multinational
Company Jobs, Mobile Prices, Laptop Prices
Disadvantages
1. Windows 98 requires at least a Pentium
Microprocessor to operate effectively. Besides more hard disk space and memory
are necassary.
2. Fewer applications have been written
specifically for it. It can however run most DOS, Windows and Windows 95
applications.
COMPUTER LANGUAGE
Language is a system for representation and
communication of information or data. Like human beings, a language or signal
is required to communicate between two persons. Similarly, we cannot obtain any
result by computer without langtage. Computer does not understand directly what
we are communicating with computer as English or Arabic, it understands only
machine language (binary codes 0-1). Computer translates English language into
machine codes through interpreter then process instructions and give us the
results.
The computer languages can be divided into two
main levels.
* Machine language (0-1)
* Symbolic language (A-Z)
Symbolic languages are further divide into two
main levels
* High-level language
* Low-level language
MACHINE LANGUAGE
Although computers can be programmed to
understand many different computer language. There is only one language
understood by the computer without using a translation program. This language
is called the machine language or the machine codes. Machine codes are the
fundamental language of the computer and is normally written as strings of
binary 0-1.
ADVANTAGES AND LIMITATIONS OF MACHINE LANGUAGE
Programs written in machine language can be
executed very fast by the computer. This is mainly because machine instructions
are directly understood by the CPU and no translation of program is required.
However, writing a program in machine language
has several disadvantage.
MACHINE DEPENDENT
Because the internal design of every type of
computer is different from every other type of computer and needs different
electrical signals to operate. The machine language also is different from
computer to computer.
DIFFICULT TO PROGRAM
Although easily used by the computer, machine
language is difficult to program. It is necessary for the programmer either to
memorize the dozens of code number for the commands in the machine’s
instruction set or to constantly refer to a reference card.
DIFFICULT TO MODIFY
It is difficult to correct or modify machine
language programs. Checking machine instructions to locate errors is difficult
as writing them initially.
In short, writing a program in machine language
is so difficult and time consuming.
SYMBOLIC LANGUAGES
In symbolic languages, alphabets are used (a-z).
symbolic languages are further divide into two main levels.
* High level languages
* Low level languages
LOW LEVEL LANGUAGE
A language which is one step higher than machine
language in human readability is called Assembly Language or a low-level
language. In an assembly language binary numbers are replaced by human readable
symbols called mnemonics. Thus a low-level language is better in understanding
than a machine language for humans and almost has the same efficiency as
machine language for computer operation. An assembly language is a combination
of mnemonic, operation codes and symbolic codes for addresses. Each computer
uses and has a mnemonic code for each instruction, which may vary from computer
to computer. Some of the commonly used codes are given in the following table.
COMMAND NAMEMNEMONIC
Add - ADD
Subtract - SUB
Multiply - MUL
Compare Registry - CR
Compare - COMP
Branch Condition -BC
Code Register -LR
Move Characters -MVE
Store Characters -STC
Store Accumulator - STA
An assembly language is very efficient but it is
difficult to work with and it requires good skills for programming. A program
written in an assembly language is translated into a machine language before
execution. A computer program which translates any assembly language into its
equivalent machine code is known as an assembler.
HIGH – LEVEL LANGUAGE
A language is one step higher than low-level languages
in human readability is called high-level language. High – level languages are
easy to understand. They are also called English oriented languages in which
instruction are given using words. Such as add, subtract, input, print, etc.
high level language are very easy for programming, programmer prefer them for
software designing that’s why these languages are also called user’s friendly
languages. Every high level language must be converted into machine language
before execution, therefore every high level language has its own separate
translating program called compiler or interpreter. That’s why some time these
languages are called compiler langauges. COBOL, BASIC, PASCAL, RPG, FORTRAN are
some high level languages.
INTERPRETER
An interpreter is a set of programs which
translates the high-level language into machine acceptable form. The
interpreters are slow in speed as compared to compilers. The interpreter takes
a single line of the source code, translates that line into object code and
carries it out immediately. The process is repeated line by line until the
whole program has been translated and run. If the program loops back to earlier
statements, they will be translated afresh each time round. This means that
both the source program and the interpreter must remain in the main memory
together which may limit the space available for data. Perhaps the biggest
drawback of an interpreter is the time it takes to translate and run a program
including all the repetition which can be involved.
Compiler
A compiler converts the programmer's procedural
language program called the source code into a machine language code which is
called the object code. This object code can then be saved and run later.
Example of precedural languages using compilers are standard versions of
Pascal, COBOL, and FORTAN.
Pascal
Another language that is widely used on
microcomputers and easy to learn is Pascal, named after Blaise Pascal, a French
mathematician. This language has become quite popular in computer science educational
programs.
C/C++
C is general purpose language that also works
well with microcomputers. It is useful for writing operating systems,
spreadsheets programs, database programs and some scientific applications. C++
is a version of C that incorporates object-oriented technologies.
COBOL
COBOL which stands for Common Business-Oriented
Language is one of the most frequently used programming languages in business.
Through harder to learn than BASIC its logic is easier to understand for a
person who is not a trained programer.
FORTRAN
Short for FORmula TRANslation, FORTRAN is a
widely used scientific and mathematical language. It is very useful for
processing complex formulas. That's why many scientific and engineering
programs have been written in this language.
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Input
Output and Storage Devices
INPUT DEVICES
Input devices are used to provide data or
information to the computer. The computer follows the instructions given to it
by and input device. A variety of input devices are used with the computer
depending on the type and purpose of input information. For example, a keyboard
is commonly used to transfer data or information from human readable form to
machine readable form. Other examples of input devices are: mouse, joystick,
trackball, light pens, digitizers, scanners, optical character reader (OCR),
touch window, etc.
MOUSE
The mouse is an input device that usually
contains one or two buttons. As a user moves the mouse on a flat surface, the
mouse controls the cursor movement on the screen. When the user presses one of
the buttons, the mouse either marks a place on the screen or makes selection
from data or menu on the screen. A mouse has a sphere on its underside. This
rotates as the mouse is moved along a flat surface.
The mouse translate the direction and speed of
rotation into a digital signals that identifies the position or control, the
cursor on the computer.
A mouse can be used for many application,
ranging from games to drawing and designing products with computer graphics. It
provides an alternative for people who are uncomfortable with a keyboard but it
also can be used in combination with a keyboard to input data.
TRACKBALL
A Trackball is a pointing device almost like a
mouse turned upside down. The user controls the cursor on the screen by rolling
a plastic ball with a fingertip or wrist. To execute commands with a Trackball,
one or more buttons are pressed, much in the same way as is done with a mouse.
The cursor can be moved around on the screen by rolling the ball with a thumb
or finger.
Trackball is popular among users of laptop
computers when space is limited and may be mounted on either side of the
keyboard. For handicapped people who may have difficulty pressing keys on a
standard keyboard or using a mouse, the trackball may be the answer since it
edoes not require to moves the entire arm to use it.
SCANNER
Scanner is an input device. It is also called
Optical Reader or Digital Scanner. It scans or reads text and picture printed
on a paper and enters them directly into the computer memory.
The advantage of a scanner is that the user
needs not type the input data in. This is a lust and accurate method for
entering data into the computer. The scanner takes electronic images, of text
or pictures from the paper it breaks each image into light and dark dots and
stores them into the computer memory in machine codes. Scanned text can be
edited by OCR software. Optical Character Recognition (OCR) software translates
the scanned document into text that can be edited.
The image scanner is useful because it
translates printed images into an electronic format than can be stored in
computer's memory. The stored image can be transferred into a paint program or
directly into a word processor. You can use software to organize and manipulate
the electronic image.
KEYBOARD
A keyboard is the most commonly used input
device which helps us in simply keying in required information in a computer.
This information is subsequently stored in the computer’s memory. A keyboard
can be used effectively to communicate with the computer but considered to be
relatively slow as compared to other input devices. The keyboard is divided
into following divisions:
ALPHABETIC KEYPAD
These keys are similar to a standard typewriter
and is used to type general information.
NUMBERIC KEYPAD
These keys are used to input numeric data only.
These are very useful in case of large numeric data input because all numeric
keys can be accessed by one hand only. These keys can also be used as an
alternative to the screen navigation and editing keys.
FUNCTION KEYS
These are keys marked as F1 - F12, located
normally at the top of the keyboard. These are special keys provided to a
programmer which allow him to attach special functions to each key. Each of
these function keys are also given some special function in different packages.
SCREEN NAVIGATION AND EDITING KEYS
These keys are provided to move around in the
screen. May programs use these keys to let the user move around the screen
display. In some keyboards these keys are also provided inside the numeric
keypad as alternate keys.
The description of commands assigned to function
keys under the BASIC mode.
F1 - LIST Function - Used to display the lines
of your program on the screen.
F2 - RUN Function - Used to execute a program
from its beginning.
F3 - LOAD Function - Used to read a program from
a storage device and store it in main memory.
F4 - SAVE Function - Used to store a program on
a storage device from Memory.
F5 - COUNT Function - Used to restart a program
after it has temporarily interrupted by a stop or CTRL + BREAK.
F6 - LPT1 Function - Used to transfer data from
the video screen to the line printer.
F7- TRON Function - Refers to "trace
on". This function causes the line number of program line to be displayed
as these lines are executed.
F8 - TROFF Function - Refers to "trace
off". This function cancels TRON function.
F9 - KEY Function - Use to change the function
of the other function keys.
F10 - SCREEN Function - Used to return program
to the character mode from the graphic mode and a;so to turn off the colour.
OUTPUT DEVICES
An output device is used to display the data or
information that we receive from the computer. An output device can be used to
display or print the intermediate or final results performed by computer. A
variety of output devices are used with computer. The use of these devices
depends on the type and purpose of output. Some examples of output devices are:
Monitors, Printer, Plotters, Visual display unit (VDU), liquid crystal display
(LCD), etc.
MONITOR
To display result or output from computer, a T.V
like device is used which is called monitor. The monitors are also referred as
C.R.T (Cathode Ray Tube), V.D.U (Visual Display Unit). The monitor assist
during input from the keyboard, this display is called a soft copy. The monitor
can be of various kinds, depending on the type of application. Monitors are
categorized into two groups:
* Monochrome monitors
* Colour monitors
MONOCHROME MONITORS
Monochrome monitors are used specially for text
editing purpose. These monitors can display only one colour. Normally amber,
green or paper white.
COLOUR MONITORS
Colour monitors serves a wide range of selection
according to the application. Such as red, green, blue, Enhance Graphic Array
(EGA), Colour Graphic Array (CGA), Video Graphics Array (VGA), Super Video
Graphics Array (SVGA).
There are two types of colour monitors:
1. CRT Monitor
2. LCD Monitor
CRT MONITOR
The CRT monitors are a lot like television set,
using the same CRT or Cathorde Ray Tube technology. The CRT monitor has two
major parts; the screen and the cathode ray tube (CRT). The screen is the front
of the monitor and CRT is fitted inside the monitor.
LCD OR FLAT PANEL MONITOR
Another monitor type is LCD or Liquid Crystal
Display. LCD monitors are a lot like CRT monitors without the bulkiness but
they do not have CRT. LCD monitors use a flat lightweight surface filled with
millions of tiny glass bubbles, each having a phosphoric covering. These
phosphoric coverings glow to create an image. LCD screens provide clarity and
flicker-free viewing.
PRINTER
A computer peripheral that puts text or a
computer generated image on paper or on another medium, such as a transparency.
Printer can be categorized in several ways the most common distinction is
IMPACT and NON-IMPACT.
IMPACT PRINTING
Is the method used by the conventional type
writers. In some type of impact printing a metal “hammer” embossed with a
character strikes a print ribbon, which presses the characters image into
paper. In other types the hammer strikes the paper and presses it into the
ribbon characters created through impact printing can be formed by either a
solid font or dot matrix printing mechanism.
NON – IMPACT PRINTING
Does not depend on the impact of metal on paper.
In fact no physical contact at all occurs between the printing mechanism and
the paper. The most popular non-impact methods today utilize thermal transfer,
ink-jet.
TYPES OF PRINTERS
DOT MATRIX PRINTER
Any printer that produces character made up of
dots using a wire pin printed head. The quality of output from a dot matrix
printer depends largely on the number of dots in the matrix, which might be low
enough to show individual dots or might be high enough to approach the look of
fully formed characters. Dot matrix printers are often categorized by the
number of pins in the printer head typically, 9 or 24.
LINE PRINTERS
Any printer that prints one line at one time, as
opposed to one character at a time or one page at a time. Line printer
typically produce the 11 by 17 inch “computer” printout. They are high speed
devices and are often used with mainframes, minicomputers, or networked
machines rather than with single user system. Types of line printers include
chain printers and band printer.
LASER PRINTERS
An electrophotographic printer that is based on
the technology used by photocopiers. A focussed laser beam and a rotating
mirror are used to draw an image of the desired page on a photosensitive drum.
This image is converted on the drum into an electrostatic charge, which
attracts and holds toner. A piece of electrostatically charged paper is rolled
against the drum, which pulls the toner away from the drum and onto the paper.
Heat is then applied to fuse the toner to the paper. Finally, the electrified
charge is removed from the drum and the excess toner is collected. By omitting
the final step and repeating only the toner application and paper handling
steps, the printer can make multiple copies.
DAISY WHEEL PRINTER
Daisy wheel printer are some times called letter
quality printer because they are often used to produce attractive
correspondence. The D.W.P is a flat circular device made of metal with
character embossed on it. As this wheel spins at a very high speed the hammer
hits the specific character against the ribbon which presses against the paper.
THERMAL TRANSFER PRINTER
It is a kind of non-impact printer. In
electrothermal printing, characters are burned on to a special paper by heated
rods on a print heat. They transfer ink from a wax-based ribbon onto plain
paper. These printer can support high quality graphic.
INK – JET PRINTER
It is a kind of non-impact spray small dots of
electrically charged ink onto a paper to form images. Ink jet printer are
flexible enough to be used as plotters.
PLOTTER
Plotter is a special output device, which is
used to produce high quality, perfectly proportional hard copy output. Plotters
are designed to produce large drawings or images such as construction plans for
buildings or blue prints for mechanical devices. Plotters have been used in
automotive and aircraft design, topological surveys, architectural layouts and
other similar complex drafting jobs.
A plotter is composed of a pen, a move-able
carriage, a drum and a holder for chart paper. Both the pen and the paper can
move up and down and back and forth. This permits very detailed drawings. Some
plotter having coloured pens can make coloured drawings also.
There are two types of plotters, which are as
follows:
1. Drum Plotter
2. Flatbed Plotter
DRUM PLOTTER
On the drum plotter, the pens, and the drum move
concurrently in different axes to produce the image. Drum plotters are used to
produce continuous output, such as plotting earthquake activity, or for long
graphic output, such as structural view of a skyscraper.
FLATBED PLOTTER
On some flatbed plotters, the pen moves in both
axes while the paper remains stationary. However, on most desktop plotters,
both paper and pen move concurrently in much the same way as on drum plotters.
SECONDARY STORAGE DEVICES
Secondary storage devices are also called backup
storage because it is used to store data. Volume of data on permanent basis
which can be partially transferred to the primary storage, when required for
data processing. Afterwards these devices are comparatively cheap and provide
greater space to store the data /instructions are stored on secondary storage devices
in the same binary codes as in primary storage.
NEEDS OF SECONDARY STORAGE DEVICE
The storage capacity of the primary storage of
today’s computer is not sufficient. To store a large volume of data as a result
additional memory called secondary storage is needed with most of the computer
system.
These devices also provides the fast
communication than I/O devices. The internal memory of a computer is a volatile
memory. Therefore, we cannot save the data permanently. In that case we require
secondary storage device which provide the facility to store the data for
future use.
RANDOM ACCESS DEVICES
Random Access Devices are those devices on which
we can directly access the data. These devices are comparatively provide the
fast communication.
For example, hard disk, floppy disk, optical
disk.
FLOPPY DISK
A floppy disk, also called simply a diskette or
disk, is a small flexible Mylar disk coated with iron oxide on which data are
stored. The floppy disk has been around since early 1970s, today it is available
in three 3½ inch, 5¼ inch and 8 inch sizes. The 5¼ and 8 inch diskettes are
covered by stiff protective jacket with different holes. The central big hole
called hub ring which is used to hold by disk drive during rotation. The
elongated read write window is used to read and write data through read/write
head. The small hole next to the hub ring is called index hole which is used to
locating data through computer. The cut out on the side of the floppy disk is
called write protect notch. If we cover this opening with a piece of paper then
we can’t write data on to disk.
In small diskette a hard plastic cover and
protective metal is used to protect disk. Before using a disk we have to format
a disk in which disk is divided into tracks and sectors for storing the data.
Diskettes may be double sided and single sided while the storage capacity
become less or more.
Floppy diskettes are more convenient to use with
microcomputers. A floppy disk which is a random access device can access data
fast than magnetic tape.
SEQUENTIAL ACCESS DEVICES
Sequential Access Devices are those in which we
can access the data one by one in a sequence. These devices provide slow
communication as compared to Random Access Device.
MAGNETIC TAPE
Magnetic tape is a sequential access device
about one half or one fourth inch in size and made of Mylar (a plastic
material) coated with a thin layer of iron oxide. Data can be read and write
through a device which is called tape drive. The read/write head of tape drive
which is an electromagnetic component read, write and erase data from magnetic
tape. Magnetic tape is divided into nine separate strips or tracks in which
eight tracks are used to store data and ninth track is used for error checking
bit.
Magnetic tape can store large quantities of data
therefore they are erasable, usable and durable secondary storage device. But
it can use with large computers.
HARD DISK
Hard disk is a thin circular metal plate coated
both side with a magnetic material. A hard disk pack consist of a number of
disk mounted on central shaft which rotate at a speed of 2400 rpm or more. In a
hard disk information is stored on both the surfaces of each disk plate except
the upper and the lower surfaces of the bottom plate which are not used.
Information is recorded on the track of the disk surfaces in the form of
invisible tiny magnetic spot. The presence of a magnetic spot represent 1 bit
and its absence represents 0 bit.
Hard disk are potentially very high capacity
storage devices typically in the range of 20 megabyte to 1 gigabyte. Data are
recorded on the tracks of a spinning disk surface and read from the surface by
one or more read/write heads. There are two basic types of disk system.
1. Moving head
2. Fixed head
MOVING HEAD
The moving head consist of one read/write head
for each disk surface mounted on an axis and which can be moved in and out. In
this system each read/write head moves horizontally across the surface of the
disk. So that it is able to access each track individually. Information stored
on the tracks which constitute a cylindrical shape through the disk pack are
therefore accessed simultaneously.
FIXED HEAD
In the fixed head system the axis are
non-movable. A large number of read/write heads are distributed over the disk
surfaces. One head for each track as a result no head movement is required and
therefore information is accessed more quickly.
Optical Dist
An Optical disk can hold 4.7 gigabytes of data.
It makes an immense amount of information available on a micro computer.
Optical disks are having great impact on a storage technology these days. In
optical disk technology a laser beam alters the surface of a plastic or
metallic disk to represent data. To read the data a laser scans these areas and
sends the data to a computer chip for conversion.
There are four kinds of optical disks available.
1. CD-ROM
2. CD-R
3. Erasable Optical Disks
4. DVD
CD-ROM
CD-ROM stands for Compact Disk Only memory.
Unlike floppy disk and hard disk. Which use magnetic charge to represent 1s and
0s, optical disk use reflected light. On a CD-ROM disk 1s and 0s are
represented by flat areas and bumpy areas (called pits) on its bottom surface.
The CD-ROM disk is read by a laser that projects a tiny beam of light on these
areas. The amount of reflected light determines whether they are represents a 1
or 0 Read-only means it cannot be written on or erased by the user.
CD-R
CD-R stands for CD Recordable. CD-R disk can be
written to once. After that they can be read many times without deterioration
and can't be written on or erased.
Erasable Optical Disks
Erasable Optical Disks are like CD-R except that
they can be written to many times. There are two basic types of erasable
optical disks. CD-RW which stands for compact disk rewriteable and MO which
stands for magnetic optical.
DVD
DVD stands for digital versatile disk. DVD disks
and disk drives and very similar to CD-ROM except that more data can be packed
into same amount of space.DVD-ROM disks have a capacity of 4.7 gigabytes. They
are being used for a variety of high-capacity needs such as recording and
playing ful-length motion pictures advanced multimedia games and interactive
encyclopedias.
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Micor Computers
Introduction
Computers are the electronic devices that can
follow instructions to accept input process that input and produce information.
From capability point of view there are four types of computers as mentioned in
the previous chapter.
1. Micro Computers
2. Mini Computers
3. Mainframe Computers
4. Super Computers
1. Micro Computers
The most widely used and fastest growing type of
computer is the micro computer. There are two categories of micro computers
desktop and portable. Desktop computers are small enough to fit along the side
of a desk and yet are too big to carry around. Personal computer are the type
of desktop. Portable computers are the micro computers that are small enough
and light enough to move from one place to another. There are four categories
of portable computers.
i. Laptops
ii. Notebooks
iii. Sub notebooks
iv. Personal Digital Assistants.
Components of Computer
The computer itself the hardware has many parts
but each fall into one of four categories.
1. Processor
2. Memory
3. Input and Output Devices
4. Storage Devices.
Only first two categories will be discussed in
this chapter, whereas next two categories will be studied in the subsequent
chapter.
The CPU or Processor
The part of the computer that runs the program
(executes processor) is known as the processor or central processing unit. The
processor is like the brain of the computer the part that organizes and carries
out the instructions that come from either user or software. The central
processing unit has two components the control unit and the arithmetic logic
unit.
Control Unit
The Control unit tells the rest of the computer
system how to carry out a program's instruction. It directs the movement of the
electronic signals between teh memory which temporarily holds data, instruction
and processed information and the arithmetic logic unit. It also direct the
signal between the CPU and the input and output devices.
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Arithmetic-logic Unit
The arithmetic logic unit usually called ALU
performs two types of operations arithmetic and logical. The arithmetic
operations are the fundamental math operations addition, substraction,
multiplication and division. Logical operations consists of comparisons. i.e.
two pieces of data are compared to see whether one is equal to (=), less than
(<) or greater than (>) the other.
Memory (RAM)
Computer has two types of memory random access
memory (RAM) and read only memory. (ROM) In this chapter only RAM will be
studied whereas ROM will be studied later. RAM also known as primary memory
internal memory or main memory hold.
- Data for processing
- Instruction for processing the data that is the program
- Information that is processed data waiting to be output
and sent to secondary storage such as floppy disk in a disk drive.
One of the most important fact
to know about memory is that part of its content is held only temporarily. In
other words, it is stored only as long as computer is turned on. When the
machine is turned off the contents immediately vanish.
The next important facts of know about memory is
that its capacity varies in different computers.
Classification of Computers
Types of Computers
1. Analog Computers
Analog computers are used to process continuous
data. Analog computers represent variables by physical quantities. Thus any
computer which solve problem by translating physical conditions such as flow,
temperature, pressure, angular position or voltage into related mechanical or
electrical related circuits as an analog for the physical phenomenon being
investigated in general it is a computer which uses an analog quantity and
produces analog values as output. Thus an analog computer measures
continuously. Analog computers are very much speedy. They produce their results
very fast. But their results are approximately correct. All the analog
computers are special purpose computers.
2. Digital Computers
Digital computer represents physical quantities
with the help of digits or numbers. These numbers are used to perform
Arithmetic calculations and also make logical decision to reach a conclusion,
depending on, the data they receive from the user.
3. Hybrid Computers
Various specifically designed computers are with
both digital and analog characteristics combining the advantages of analog and
digital computers when working as a system. Hybrid computers are being used
extensively in process control system where it is necessary to have a close
representation with the physical world.
The hybrid system provides the good precision
that can be attained with analog computers and the greater control that is
possible with digital computers, plus the ability to accept the input data in
either form.
Classification of Computers According to Size
1. Super Computers
Large scientific and research laboratories as
well as the government organizations have extra ordinary demand for processing
data which required tremendous processing speed, memory and other services
which may not be provided with any other category to meet their needs.
Therefore very large computers used are called Super Computers. These computers
are extremely expensive and the speed is measured in billions of instructions
per seconds.
2. Main Frame Computers
The most expensive, largest and the most
quickest or speedy computer are called mainframe computers. These computers are
used in large companies, factories, organizations etc. the mainframe computers
are the most expensive computers, they cost more than 20 million rupees. In
this computers 150 users are able to work on one C.P.U. The mainframes are able
to process 1 to 8 bits at a time. They have several hundreds of megabytes of
primary storage and operate at a speed measured in nano second.
3. Mini Computers
Mini computers are smaller than mainframes, both
in size and other facilities such as speed, storage capacity and other
services. They are versatile that they can be fitted where ever they are
needed. Their speeds are rated between one and fifty million instructions per
second (MIPS). They have primary storage in hundred to three hundred megabytes
range with direct access storage device.
4. Micro Computers
These are the smallest range of computers. They
were introduced in the early 70’s having less storing space and processing speed.
Micro computers of todays are equivalent to the mini computers of yesterday in
terms of performing and processing. They are also called “computer of a chip”
because its entire circuitry is contained in one tiny chip. The micro computers
have a wide range of applications including uses as portable computer that can
be plugged into any wall.
5. Laptop Computers
The smallest computer in size has been
developed. This type of small computers look like an office brief case and
called "LAPTOP" computer. The laptops are also termed as
"PORTABLE COMPUTERS." Due to the small size and light weight, they
become popular among the computer users. The businessmen found laptop very
useful, during traveling and when they are far away frm their desktop computers.
A typical laptop computer has all the facilities available in microcomputer.
The smallest laptops are called "PALMTOP"
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History of Computers
At the early age people used pebbles, stones,
sticks, scratches, symbols and finger tips to count, which were later replaced
by numbers.
The history of computing is divided into three
ages during which man invented and improved different types of calculating
machines. These ages are,
* Dark age - 300 BC to 1890
* Middle age - 1890 AD to 1944
* Modern age - since 1944 AD
Dark Age (3000 BC to 1890 AD
ABACUS
About 3000 years BC, Chinese developed the first
calculating machine named Abacus or Soroban.
Abacus consists of a rectangular wooden frame
having rods which carry round beads. Counting is done by shifting the beads
from one side to another.
OUGHTRED’S SLIDE RULES
In 1632 AD William Oughtred, an English
mathematician developed a slide rule. This device consists of two movable rules
placed side by side on which number were marked.
PASCAL’S CALCULATOR
Blasé Pascal (1623-1662), a French developed the
first mechanical calculating machine in 1642. This machine consists of gears,
wheels and dials. It was capable of adding and subtracting operations.
GOTTEFRIED WILHOLM LEIBNITZ
In 1671, a German, Gottfried Von Leibnitz
(1646-1716) improved Pascal’s calculator to make it capable of performing all
maths operations.
JACQUARD’S LOOM
In 1801, a French, Joseph Marie Jacquard
developed the first punch card machine.
BABBAGE DIFFERENCE ENGINE
Charles Babbage (1792-1871) an English
mathematician also called Father of modern computer. As he gave the true
concept of computer at Cambridge University, he developed Babbage Difference
Engine in 1823 and Babbage Analytical Engine in 1833.
Lady Ada Augusta an assistant of Babbage is
called the first programmer.
Middle Age (1890 AD TO 1944 AD)
DOCTOR HERMAN HOLLERITH
In 1880s Herman Hollerith an American developed
a machine which used punch card system. The machine could sense and punch
holes, recognize the number and make required calculations. This machine was
first used in 1890s by American Census Bureau.
HOWARD AIKEN- MARK-1 COMPUTER
In 1937, Professor Howard Aiken build the first
electro-mechanical computer Mark-1, by trying to combine Babbage’s theory and
Hollerith’s punching technologies. He completed his project in 1944 with the
help of IBM Engineers.
Mark 1 could multiply two, twenty digit numbers
in 5 seconds and made a lot of noise. It had a shape like a monster about 50
feet long, 8 feet high, having wiring of length equal to distance from Lahore
to Gilgit or Karachi to Bahawalpur (800km) and had thousand ends of
electro-magnetic relays.
ABC (ATANASOFF BERRY COMPUTER)
ABC a special purpose computer was developed in
1938 by Dr. John Vincent Atanasoff and Clifford Berry at Iowa State College,
USA.
Modern Ages (Since 1944 AD)
JOHN VON NEUMAN
In 1945, Dr. John Von Neuman suggested the
concept of Automatic Data Processing (ADP) according to the stored program and
data. ENIAC
(FIRST ELECTRONIC COMPUTER)
Electronic Numerical Integrator And Calculator
(ENIAC) was the first electronic computer made in 1946 by John Presper Eckert
and John Williams Mauchly, at the University of Pennsylvania, USA. This was
based on decimal number system and it has no memory.
It could perform 5000 additions or 350
multiplications in one second. It contained 18000 vacuum tubes, 70,000
resistors, 10,000 capacitors and 60,000 switches and occupied a two room car
garage. It consumed 150 kW of power. It weighed 27 tons.
EDSAC (FIRST STORED PROGRAM COMPUTER)
Electronic Delay Storage Automatic Computer
(EDSAC) was first computer based on stored program concept. It was completed by
Mourice Wilkes at Cambridge University in 1949.
EDVAC
Electronic Discrete Variable Automatic Computer
(EDVAC) was built by John Williams Mauchly, John Presper Eckert at Moore
School, Pennsylvania in 1951.
UNIVAC (FIRST COMMERCIAL COMPUTER)
UNIVersal Automatic Computer (UNIVAC) was the
first commercially used computer made by John Presper Eckert and John Williams
Mauchly in June 14, 1951.
Generations of Computer
First Generation of Computer (1946-1959)
Main Features
* Major Innovation - Vacuum Tubes
* Main Memory - Punched Cards
* Input Output Devices - Punched cards and
papers
* Languages - Low level machine language
* Operating System - No operating system, human
operators to set
switches
* Size - Main frame for example ENIAC, EDVAC, UNIVAC
The duration lasted from 1946-1959 was based on
vacuum tubes. These vacuum tubes were about the size of 100 watt light bulb and
used as the internal computer component. However because thousands of such
bulbs were used, the computers were very large and generate a large amount of
heat, causing many problems in temperature regulation and climate control.
In this generation input and out put device
(punched card) that was used fro data storing purpose were very slow. The
computers were operating manually and the language used was a low level machine
language (symbolic language) with binary code that required a high programming
skill. ENIAC, EDVAC, UNIVAC and Mark-1 were some of the major inventions of
this generation.
Advantages of First Generation
1. Vacuum tubes were used as electronic
component.
2. Electronic digital computers were developed
for the first time.
3. These computers were the fastest calculating
devices of their time.
4. Computations were performed in millisecond.
Disadvantages of First Generation
1. Too large in size.
2. They were unreliable.
3. Induce a large amount of heat due to the
vacuum tubes.
5. Not portable.
6. Limited commercial use.
Second Generation of Computers (1959-1964)
Main Features
* Major Innovation - Transistors as main
component.
* Main Memory - RAM and ROM.
* External Storage - Magnetic tapes and Magnetic
Disk.
* Input Output Devices - Magnetic tapes and
Magnetic Disk.
* Languages - Assembly language, some high level
languages for Example BASIC, COBOL, FORTRAN.
* Operating System - Human handles punched card.
* Size - Main frame for example IBM-1401,
NCR-300, IBM-600 etc.
The period of this generation is from 1959 to
1964. During this period transistor were used for internal logic circuits of
computers. These computers could execute 200000 instructions per second. The
input/output devices became much faster by the use of magnetic table. During
this period the low level programing language were used however the high level
programming languages such as FORTRAN and COBOL were also used. The problem of
heat maintenance was solved and size of computer reduced, while speed and
reliability were increased. Many companies manufactured second generation
computers and many of those for business applications. The most popular second
generation computer was IBM-1401, introduced in 1960, while the following
computers were used by many business organizations. IBM-1400 series, IBM-1600
series, UNIVAC-III, NCR-300 etc.
Advantages of Second Generation
1. Smaller in size as compares to 1st
generation.
2. Much more reliable.
3. Less heat generated.
4. Computation was performing in micro second.
5. Less hardware and maintenance problem.
6. Could be used for commercial use.
Disadvantages of Second Generation
1. Very costly for commercial use.
2. It still required frequent maintenance.
3. Frequent cooling also required.
Third Generation of Computers (1965-1970)
Main Features
* Major Innovation - Integrated circuit (ICs) as
basic electronic component.
* Main Memory - PROM and DRAM.
* External Storage - Improve disk (Floppy Disk)
* Input and Output Devices - Keyboard for input,
monitor for output.
* Languages - More high level languages.
* Operating System - Complete operating systems
were introduced.
* Size - Mini, for example: IBM SYSTEM / 360,
ICH-360, HONEY WELL-316 etc.
In this generation the integrated circuits (IC)
were used. Integrated circuits contain many electronic components on a single
chip. The disk oriented systems wee made at the end of this generation. The
size of computer became very small with better performance and reliability.
High level programming languages were extensively used. In 1969 the first
microprocessor chip INTEL 4004 was developed but it was used only in calculators.
The faster input/output devices made possible multi-processing and multi
programming. Where by a number of input terminals could be run virtually at the
same time on a single centrally located computer. The famous computer were
IBM-360, IBM-370, UNIVAC 9000 series etc.
Advantages of Third Generation
1. Smaller in size as compared to second
generation.
2. More reliable.
3. Portable
4. Less electricity consumption.
5. Heat generation was rare.
6. General purpose computer.
Disadvantages of Third Generation
1. Air conditioning was required in many cases
due to ICs.
2. Very advance technology was required to make
the ICs.
Fourth Generation of Computers (1971-1981)
Main Features
* Major Innovation - LSIC and VLSIC (Micro
Processor)
* Main Memory - EPROM and SRAM.
* External Storage - Floppy Disk and Hard Disk.
* Input and Output Devices - Monitor for output.
* Languages - Languages and application
softwares.
* Operating System - MS-DOS and PC-DOS
* Size - Micro computer e.g. IBM-PC, Apple
Macintosh etc.
The Integrated circuits were more developed and
called Small scale integration (SSI), after some time the SSI were more
developed and termed as Large scale integration (LSI). There was a great
versatility of input/output devices. In 1971, a powerful microprocessor chip
INTEL 8008 was introduced. The first microprocessor which is used in personal
computers (PC) was INTEL 8080. The 8 inch floppy disk was also introduced in
1971, while hard disk was introduced in 1973. The 5.25 floppy disk was first
time used in 1978. The optical disk was developed in 1980. First portable
computer "Osborne I" was marketed in 1981. IBM-3033, IBM-370, IBM
system 34, IBM system 36, Cray-I, CP/M etc were introduced in this generation.
Advantages of Fourth Generation
1. Smaller in size and much reliable.
2. No cooling system required in many cases.
3. Much faster computation.
4. Portable and cheap.
5. The heat generated was negligible.
6. Totally general purpose computer.
Disadvantages of Fourth Generation
1. Very advanced technology was required to
fabricate to the ICs.
Fifth Generation (1981-Onward)
Main Features
* Major Innovations - ULSIC (Ultra large scale
integrated circuit)
* Main Memory - EEPROM, SIMM and DIMM.
* External Storage - Modified magnetic and
Optical disks.
* Input/output Devices - Keyboard, Pointing
Device, Scanner as input and Monitor as main output.
* Languages - AI (Artificial Intelligence)
Expert systems.
* Operating System - GUI based e.g. Windows 95,
Windows NT.
* Size - Very small in size example: Laptop,
Note book, Digital Diary, Palm top and Pocket PC.
This generation is started from 1981 and still
continued, new technologies are adopted to fabricate IC chips, such as electron
beam, X-rays or laser rays. The Very Large Scale Integration
(VLSI) was developed, so the computer became
much smaller than ever before. New memory storage device like bubble memory,
optical or memory are being designed. the new computer will be controlled by
using human voice and will work by giving command in our own language. Future
computer will in some way to be intelligent and capable of making decision.
Advantages of Fifth Generation
1. Very large storage capacity.
2. Long bit processor builds.
3. Artificial Intelligence Language developed.
Read more: History of Computers http://www.friendsmania.net/forum/1st-year-notes-computer-notes/25529.htm#ixzz35A9bR5Hw
IT introduction - Introduction To IT & Definition of IT
Definition of Information Technology
The concept and the term information technology
is so broad that no precise and comprehensive definition, encompassing all the
aspects of IT, can be given. Because information technology is set of various
diversified and multidimensional technologies. Despite that we may try to
define
IT is a set of technologies that merge computing
with high speed communication communication links carrying data, sound and
videos.
Examples of information technology include
personal computers, of course, but also new forms of telephones, televisions
and various handheld devices, such as personal digital assistants.
It should be noted that there are two parts of
this definition, the computers and communications.
A computer is a programmable, multi-use machine
that accepts data, the raw facts and figure, and process or manipulates it into
information that we can use, such as summaries totals or reports. Its purpose
is to speed up problem solving and to increase productivity.
Communication technology also called
telecommunication technology consists of electromagnetic devices and systems
communicating over long distances. The principle examples are telephone, radio
broadcast, television and cable TV. More recently, there has been an addition
of communication among computers, when people tell you that they "went
online" with the Internet. To be online means using a computer or other
device connected through a voice or data network, to access information and
services from another computer or information device.
Now the students may be convinced that there a
use of computer is not information technology, rather it is a set of
technologies. Computer is just a part of it, through the most important and
amazing.
Importance of Computers
The computer is truly an amazing machine. Few
tools, other than computers, can help you perform so many different tasks in so
many areas of life. That's why computers have become so fundamental to modern
society that without them our society would be a primitive one. They are such
flexible tools that most people in the business community use them every day.
Office workers use them to write letters, keep employee rosters, create budgets
communicate with coworkers, find information, manage projects and so on. Many
business people even when they are away from the office, for instance,
salespeople use computers to manage accounts and make presentation.
Computers are also vital accounting departments.
For organizing and manipulating large sets of numbers, which accounting
departments do daily, computers are now considered essential. Even small
business, which can comprise just a single person can afford to set up
sophisticated accounting systems using a personal computer and affordable
accounting and financial packages.
Even if you do work in a business computers
effect you every day. Any time you go to the bank call information for a phone
number or buy something out of a catalog, you are benefiting from the power and
speed of computers. Even when you buy groceries and gasoline, you may be
interacting with computers.
Capabilities of Computer
Besides being a multi-use device a computer has
a number of remarkable capabilities namely very fast speed, accuracy,
consistency, reliability and sufficiently large memory.
Speed
A computer can perform various activities by
executing programs at a very fast speed. For example it can perform tedious
calculations immediately. While a man would take very large time to perform the
same job.
Accuracy
Along side speed the tasks performed by a
computer are almost accurate. However you may some times come across program logic
error, a procedural error or an error in data. But these error are not of
computer rather these are human error, i.e. it is the man who makes these error
while interacting with computer.
Consistency
During performing a tedious task a man can get
tired and he may want to change the nature of the job he is performing or at
least he may to change the way he perform his task. But as computer works
according to a preprogrammed way. i.e. it has to follow the instruction given
to it in the form of a program computer has to perform required tasks with
consistency.
Reliability
As mentioned above, the computers have the
capabilities to perform a required task in accordance with the preprogrammed
instructions with a great speed, accuracy and consistency. Hence the job
performed by a computer is highly reliable.
Memory Capability
Man has very limited memory and recalling
ability, whereas computer not only have a great capability of storing data in
its memory but can also recall this huge amount of data instantly. For example,
insurance companies use mainframe computers to process information about
millions of policy holders. Obviously no man, even the genius people, can store
such huge amount of data in his memory. Even if he could it would be impossible
for him to recall required information instantly. While computer can do this
job easily.
Uses of Computers
Can you think of a field where you can perform
your job efficiently and productively, without the use of computer? Certainly
you can't. No matter what career you choose the use of computers will affect
you life for this wonderful machine has encompassed almost all the aspects of
human life. Some of the fields where in computers are being used extensively
are:
Information Management
As computers are excellent tools for managing
large quantities of information, they are being extensively used by various
organizations for various purposes like airline reservations, student
registration, billing and countless others.
Communication
Computer specially combined with tools of
telecommunications has become the most effective tool of communication. All the
organizations need to communicate with each other, besides communicating with
the various departments of the same organization in order to run their day to
day business efficiently. The use of computers has facilited this task.
Moreover now one can instantly communicate with the people all around the world
through internet.
Education and research
Perhaps the most fruitful and productive use of
computers has been in the fields of education, scientific and engineering
research. The use of computers has converted education into edutainment.
Engineers and scientists are utilizing computers as a tool of experimentation
design and development. In this respect computerized design (CAD) provides a
sophisticated array of tools.
Business and E-Commerce
The emergence of the concept of e-commerce is
the result of wide spread use of computers in business. This has motivated
almost all the business community to redefine the customer-salesperson
relationship. Now you need not to go to super market for shopping for you may
place you orders electronically. E-banking and E-commerce has reduce the costs
of distribution of commodities and services tremendous.
E-Government
The idea of e-government i.e. providing
government service electronically using computers is under its way. The NADRA
is an example of utilizing computers for this purpose. Besides the use of
computers in the field of health and medicine, agriculture and industries has
not only revolutionized these fields but has reduced the cost of production and
distribution of goods and services resulting in an over all increase in the
standard of living of a common man.
The Impact of Information Technology
The rapid advancement in the field of computers
and information technology is having its consequences not only on the
organizations but not individuals too. In this connection the most important
impact of computers and information technology is undoubtedly the emergence of
globalization. Computer based communication is turning the world into a global
village. We can communicate electronically using the tools of information
technology with the people on the other side of the world as easily as we might
have a coversation with a neighbor. Besides the process of globalization
information technology is influencing the society in the following ways.
Better Planning and Decision Making
Computer based information systems are
facilitating decision making through better planning. As the information
technology has improved the communication to the unbelievable extent, the
multinational organizations are pooling their information for the better future
forecast and planning.
Better Control of Resources
It is essential particularly in business
organizations to check whether the planned goals and objectives are being
achieved or not. In this respect computer system due to their power and
reliability for accuracy can be utilized to measure actual performance levels
and to compare these levels with panned standards. Not only this rapid
communication of information through the use of information technology provides
the business firms with an opportunity to compare its operational efficiency
with that of other firms.
Greater Efficiency of Operation
Not to speak of IT and computer experts and
professionals even a lay man in the street can realize that the use of
computers along with other tools of information technology has improved the
efficiency of operation particularly in industrial process.
Read more: IT introduction - Introduction To IT & Definition of IT http://www.friendsmania.net/forum/1st-year-notes-computer-notes/25528.htm#ixzz35A9ksqRB