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Computer is an electronic machine, which takes input, process it and give us a desire output.
OR Computer is an electronic data
processing machine which takes the input, stores the data in its memory
then process it with the help of Arithmetic Logic Unit (A.L.U) under the
supervision of Control Unit (C.U) and then give us the output according
to the instructions (Program). OR The
word computer is derived from a Latin word "Computer" which
means to count or to calculate. The computer is an extension of human
mind which can perform several tasks with a great speed. Computers are
just like a dumb servant who cannot take any decision by itself they
only do what they are told to do so.
Data processing often referred as D.P. Data Processing is a process of collecting the data together and converting the data into information. The method used for collecting the data may be manual, mechanical or electronic. Data processing is a term mostly associated with business and commercial work. Since computers are being used in the processing of data the term "electronic data processing" may also be used. ELECTRONIC DATA PROCESSING (E.D.P) Data processing means transformation of data into more meaningful results for carrying out scientific, business activities. The result of data processing is called "information". The transformation of data consist of a sequence of operations. The sequence is called "procedure". Input ® Processing ® Output Data processing is a system which takes data as an input, carries out the required processing on the data and produces the information. The system is called "MANUAL" when processing is performed by human beings and "AUTOMATIC" when machines are used. When computers are used for data processing the system is called "Electronic Data Processing". ELEMENTS OF E.D.P There are five basic elements in
a processing system which uses a computer for processing data. These are
hardware, software, user program, procedure and personels. 1. HARDWARE All the physical parts which makes up a
computer system called hardware i.e. all the devices or peripherals
which performs the data processing operations. 2. SOFTWARE Software consists of programs and
routines whose purpose is to make the computer useable for the user.
These software normally supplied by computer manufacturers or software
manufacturers. 3. USER PROGRAM A program consist of a related
instructions to perform operations. A data processing job may require a
number of programs. 4. PROCEDURE The operations of data processing
system requires procedure for use, in preparing data, for operating the
computer and distributing the output after processing. 5. PERSONNELS E.D.P basically needs three kinds of
skilled personnels. a.
System Analyst b.
Progammer c.
Operator a) SYSTEM
ANALYST System Analyst studies information
needs and data processing requirements, design a data processing system
and prepare specification. b) PROGRAMMER A Programmer writes a programmer on
specification by System Analyst. c) OPERATOR An Operator is a person who operates
the computer system.
The electronic logic of micro computer
is based on a single printed circuit board which is stored in a case and
provided with a keyboard for data entry and a monitor. The I/O logic may
support a range of peripherals such as printer, disk, mouse etc.
Microcomputer have operating system and peripheral connectivity to
support microcomputers. An electronic device which can perform
a range of basic logical functions upon the given input signal. The
device also contains memory and features which enable it to be
programmed to perform sequences of such functions. A typical microprocessor consists of a
series of a microprocessor is described as a microprogrammed device
usually the microprogram is built into the microprocessor and cannot be
altered.
TECHNOLOGICAL
EVOLUTION OF COMPUTERS OR HISTORY
AND DEVELOPMENT OF COMPUTERS OR AGES AND GENERATIONS OF COMPUTER 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, a.
Dark age300 BC to 1890 AD b.
Middle age1890 AD to 1944 AD c.
Modern agesince 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 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. 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. Over time, computers changed. They
improved in speed, power and efficiency. The changes are recognized as a
progression of generations, each characterized by specific developments.
FIRST GENERATION (1951-
1959) First generation computers were powered
by thousands of vacuum tubes. The UNIVAC 1 and others were large because
of the massive number of tubes that were required. The vacuum tubes
required great amount energy and they generated much heat. The computer
memory was stored on magnetic tapes. Most of the data were entered into
the computer on punch cards. Machine Language (0-1) and Assembly
Languages were used to program the computers. Operation was under human
control. SECOND GENERATION (1959-
1965) The device that characterized the
second generation computers was the transistor. The transistor were made
of a semiconducting material and controlled the flow of electricity
through the circuit. Transistors were a Transistor were less expensive and
smaller and emitted less heat than vacuum tubes. Transistors were not so
fragile as vacuum tubes. Although magnetic tape was still the most
commonly used external storage, magnetic disk was used so data could be
located more rapidly. Programming languages also become more
sophisticated. High level language (resembling English) were developed
including FORTRAN, COBOL, BASIC and PL1. THIRD GENERATION (1965-
1971) Integrated circuits signified the
beginning of third generation computers. Again computers were smaller,
more efficient and more reliable than previous generation. Unlike
transistors and circuit boards that were assembled manually, integrated
circuits (IC) were single complete electronic semiconductors or circuits
contained on pieces of silicon sometime called chips. ICs could be
manufactured by machinery, which ultimately resulted in a lower cost.
Memory technology improved many transistors could be built on a chip of
silicon. High level languages continued to be developed, including RPG
and Pascal. Keyboard. FOURTH GENERATION (1971-
PRESENT) The significant distinction for fourth
generation computers lies in the techniques of implementation of
integrated circuits by using large scale integration (LSI) of chip with
several thousand transistors. In the mid 1970s the development of (VLSI)
produced a chip containing a microprocessor. The development of (VLSI)
made the development of the microcomputer possible. Magnetic disks
become the primary means of external storage. The application programs
for microcomputers allowed home and business user to adapt their
computers for wor-processing, spread sheet manipulating, file handling,
graphics and much more.
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. A computer which process
information represented by combination of *** or discontinuous data. It
is a device for performing sequence of arithmetic and logical
operations, not only on data but on its ***. Digital computer that is
capable of performing sequences of internally stored instructions for
calculation. Digital computers are not very much fast but their results
are very much accurate. All the digital computers are general purpose
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. General purpose computers are designed
to solve a large variety of problems. The different programs can be used
to solve many problems. Most digital computers are general purpose
computers and used in business and commercial data processing. A computer designed for machine control
or process control would be different than a general purpose computer.
The special purpose computers are designed to solve specific problems.
The computer program for solving a specific problem is built right into
the computer. Most analog computers are special purpose computers. These
special purpose computers are widely used in industrial robotics. 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. 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. 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. 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 (B.I.P.S).
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.
Symbolic
languages are further divide into two main levels
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. In symbolic languages, alphabets are
used (a-z). symbolic languages are further divide into two main levels.
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. 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. 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.
INPUT DEVICES
INPUT The information entered into the computer for processing purposes is termed as input.
INPUT DEVICES Any peripheral that assist us in getting data into the computer, such as a keyboard, mouse, trackball, voice recognition system, graphical tablet or modem is termed as Input Device. There are a number of input devices available to input data into the computer system. Without these devices computer never perform any kind of work. These are the essential part used with computers and are listed below:
A device used to feed information into the computer in the shape of alphabets, numbers, puntuation marks, graphic symbols and foreign currency marks in know as Keyboard. They are used for inputting data at a comparatively very slow rate of human typing. Their major function is to enable the computer to communicate with the computer operator.
Mouse is another input device usually referred to as Pointing device. With the help of mouse we can move around the screen with no time. Nowadays mouse is always installed on AT-type computers. All type of mouse manufactured from different vendors available with two or more than two keys or buttons and a small ball, which is the guiding part where you wants to move the pointer on the screen to select any kind of option. These selections are available under WINDOWS. Mouse has a cable and a plug, which is installed into the computer from rear side with the mouse port.
Any type of joystick is always used to play games on the computer. This is an input device always used to control all possible movement around the screen during playing games. Any joystick has switches for firing and a vertical stick placed at the 90°, which is used to move and control any kind of object.
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. 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 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).
The central processing unit is
considered to be the heart of the computer system because it is the unit
where all the calculations and processing takes place. The CPU comprises
of three main units.
CONTROL UNIT The control unit directs and
co-ordinates the entire computer system and helps it in carrying out
program instructions. It controls all the activities within the computer
system, i.e., input, output and storage devices. It does not execute the
instructions itself but instead directs other parts of computer system
to do so. In simple words the CU controls the flow of data inside the
computer. ARITHMETIC LOGIC UNIT It is the most important part of the
computer system because it performs all arithmetic and logical
operations on data such as addition, subtraction, multiplication and
division and also logical comparisons such as equal to, greater than and
less than, etc. Decisions are also taken by this unit. MAIN MEMORY The main memory, also known as the
primary memory or internal storage. It is that part of the CPU that
holds programs and data that have been entered into the computer.
Intermediate processing results and output that is ready to be
transmitted to secondary storage or to an output device are also stored
in this unit. The main memory plays a very vital role in the processing
speed of a computer. A bigger memory size provides larger amount of
information to a computer for processing and hence increases the
processing speed. Main memory usually comprises of two
types, the Read Only Memory (ROM) and the Random Access Memory (RAM). RAM -
RANDOM ACCESS MEMORY RAM is the empty storage space in the
computer, the computer’s internal memory it is referred as read/write
memory. This memory area is immediately accessible to the user. Data can
easily be read from or written into the RAM locations. The information
stored in RAM is volatile i.e., when the computer is shut down and the
information stored is also lost or erased, therefore RAM is also known
as the temporary memory of the computer. ROM -
READ ONLY MEMORY ROM contains a control program called
BIOS (Basic I/O System) and an interpreter. The information stored in
ROM is available to a computer only to be read and process but cannot be
changed. The information is stored in ROM before the computer is
assembled by the manufacturers on small pieces of memory called chips.
Since it is the permanent memory of the computer therefore the
information stored in ROM cannot be lost or erased even if the computer
is turned off.
Computer is important in this
contemporary world of human efforts. The frequent use of computer
rapidly changing the nature of work. Its impact is being felt in
industries, banks, education etc. to solve the complicated and time
consuming problems. Computer can improve the efficiency of an
organization. The business person employing a computer can trim
unnecessary over time reducing dependency upon unreliable person or
outside agencies. The importance and capabilities of
computer can be discussed under three heads.
SPEED Computer is an electronic data
processing machine which can perform arithmetic and logical operations
with very much speed. It can perform million instructions per second.
That would take a person year to complete. To classify the speed of
different computers the manufacturer has the criteria of (MIPS) million
instructions per second. ACCURACY The computer must process the data
accurately. Accuracy is the prime consideration of installing computer.
Computers are universally accused of making mistakes on bills,
statements and etc. The probability of computer errors are quite often
and traceable. RELIABILITY Computer system are widely accept
because of there exceptional reliability. Computer constantly provide
the same accurate results under all operating conditions.
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