What is Computer : Computer is an electronic device that is designed to work
with Information. The term computer is derived from the
Latin term ‘computare’, this means to calculate or programmable
machine. Computer can not do anything without a Program. It
represents the decimal numbers through a string of binary digits. The
Word 'Computer' usually refers to the Center Processor Unit plus Internal
memory.
Charles Babbage is called the "Grand Father" of the computer. The
First mechanical computer designed by Charles Babbage was called Analytical
Engine. It uses read-only memory in the form of punch
cards.
Computer is an advanced
electronic device that takes raw data as input from the user and processes
these data under the control of set of instructions (called program) and gives
the result (output) and saves output for the future use. It can process both
numerical and non-numerical (arithmetic and logical) calculations.
Digital
Computer Definition
The basic components of
a modern digital
computer are: Input Device, Output Device, Central Processor
Unit (CPU), mass storage device and memory. A Typical modern computer uses LSI
Chips. Four Functions about computer are:
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accepts data
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Input
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processes data
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Processing
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produces output
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Output
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stores results
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Storage
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Input (Data):
Input is the raw information entered
into a computer from the input devices. It is the collection of
letters, numbers, images etc.
Process:
Process is the operation
of data as per given instruction. It is totally internal process of the
computer system.
Output:
Output is the processed
data given by computer after data processing. Output is also called as Result.
We can save these results in the storage devices for the future use.
Computer
Classification: By Size and Power
Computers differ based
on their data processing abilities. They are classified according to purpose,
data handling and functionality.
According to
functionality, computers are classified as:
• Analog
Computer: A computer that represents numbers by some continuously
variable physical quantity, whose variations mimic the properties of some
system being modeled.
• Personal computer: A personal computer is a computer small and low cost. The term"personal computer" is used to describe desktop computers (desktops).
• Workstation: A terminal or desktop computer in a network. In this context, workstation is just a generic term for a user's machine (client machine) in contrast to a "server" or "mainframe."
• Minicomputer: A minicomputer isn't very mini. At least, not in the way most of us think of mini. You know how big your personal computer is and its related family.
• Mainframe: It refers to the kind of large computer that runs an entire corporation.
• Supercomputer: It is the biggest, fastest, and most expensive computers on earth.
• Microcomputer: Your personal computer is a microcomputer.
• Personal computer: A personal computer is a computer small and low cost. The term"personal computer" is used to describe desktop computers (desktops).
• Workstation: A terminal or desktop computer in a network. In this context, workstation is just a generic term for a user's machine (client machine) in contrast to a "server" or "mainframe."
• Minicomputer: A minicomputer isn't very mini. At least, not in the way most of us think of mini. You know how big your personal computer is and its related family.
• Mainframe: It refers to the kind of large computer that runs an entire corporation.
• Supercomputer: It is the biggest, fastest, and most expensive computers on earth.
• Microcomputer: Your personal computer is a microcomputer.
Education : Getting the right kind of information is
a major challenge as is getting information to make sense. College students
spend an average of 5-6 hours a week on the internet.Research
shows that computers can significantly enhance performance in learning.
Students exposed to the internet say they think the web has helped them improve
the quality of their academic research and of their written work. One
revolution in education is the advent of distance learning. This offers a
variety of internet and video-based online courses.
Health
and Medicine :
Computer technology is
radically changing the tools of medicine. All medical information can now be
digitized. Software is now able to computer the risk of a disease. Mental
health researchers are using computers to screen troubled teenagers in need of
psychotherapy. A patient paralyzed by a stroke has received an implant that
allows communication between his brain and a computer; as a result, he can move
a cursor across a screen by brainpower and convey simple messages.
Science
:
Scientists have long
been users of it. A new adventure among scientists is the idea of a
“collaboratory”, an internet based collaborative laboratory, in which
researchers all over the world can work easily together even at a distance. An
example is space physics where space physicists are allowed to band together to
measure the earth’s ionosphere from instruments on four parts of the
world.
Business
:
Business clearly see the
interest as a way to enhance productivity and competitiveness. Some areas of
business that are undergoing rapid changes are sales and marketing, retailing,
banking, stock trading, etc. Sales representatives not only need to be better
educated and more knowledgeable about their customer’s businesses, but also
must be comfortable with computer technology. The internet has become a popular
marketing tool. The world of cybercash has come to banking – not only smart
cards but internet banking, electronic deposit, bill paying, online stock and
bond trading, etc.
Recreation
and Entertainment:
Our entertainment and
pleasure-time have also been affected by computerization. For example:
• In movies, computer generated graphics give freedom to designers so that special effects and even imaginary characters can play a part in making movies, videos, and commercials.
• In sports, computers compile statistics, sell tickets, create training programs and diets for athletes, and suggest game plan strategies based on the competitor’s past performance.
• In restaurants, almost every one has eaten food where the clerk enters an order by indicating choices on a rather unusual looking cash register; the device directly enters the actual data into a computer, and calculates the cost and then prints a receipt.
• In movies, computer generated graphics give freedom to designers so that special effects and even imaginary characters can play a part in making movies, videos, and commercials.
• In sports, computers compile statistics, sell tickets, create training programs and diets for athletes, and suggest game plan strategies based on the competitor’s past performance.
• In restaurants, almost every one has eaten food where the clerk enters an order by indicating choices on a rather unusual looking cash register; the device directly enters the actual data into a computer, and calculates the cost and then prints a receipt.
Government:
Various departments of
the Government use computer for their planning, control and law enforcement
activities. To name a few – Traffic, Tourism, Information & Broadcasting,
Education, Aviation and many others.
Defence:
There are many uses
computers in Defence such as:
• Controlling UAV or unmanned air-crafts an example is Predator. If you have cable I would recommend watching the shows “Future Weapons" and “Modern Marvels". The show future weapon gives an entire hour to the predator.
• They are also used on Intercontinental Ballistic Missiles (ICBMs) that uses GPS and Computers to help the missile get to the target.
• Computers are used to track incoming missiles and help slew weapons systems onto the incoming target to destroy them.
• Computers are used in helping the military find out where all their assets are (Situational Awareness) and in Communications/Battle Management Systems.
• Computers are used in the logistic and ordering functions of getting equipments to and around the battlefield.
• Computers are used in tanks and planes and ships to target enemy forces, help run the platform and more recently to help diagnose any problems with the platforms.
• Computers help design and test new systems.
Sports:
In today's
technologically growing society, computers are being used in nearly every
activity.
Recording
Information
Official statistics
keepers and some scouts use computers to record statistics, take notes and chat
online while attending and working at a sports event.
Analyzing
Movements
The best athletes pay
close attention to detail. Computers can slow recorded video and allow people
to study their specific movements to try to improve their tendencies and repair
poor habits.
Writers
Many sportswriters
attend several sporting events a week, and they take their computers with them
to write during the game or shortly after while their thoughts are fresh in
their mind.
Scoreboard
While some scoreboards
are manually updated, most professional sports venues have very modern
scoreboards that are programmed to update statistics and information
immediately after the information is entered into the computer.
Safety
Computers have aided in
the design of safety equipment in sports such as football helmets to shoes to
mouth guards
A computer can process data, pictures,
sound and graphics. They can solve highly complicated problems quickly and
accurately. A computer as shown in Fig. performs basically five major
computer operations or functions irrespective of their size and make. These are
1) it accepts data or
instructions by way of input,
2) it stores data,
3) it can process data as required by the user,
4) it gives results in the form of output, and
5) it controls all operations inside a computer.
2) it stores data,
3) it can process data as required by the user,
4) it gives results in the form of output, and
5) it controls all operations inside a computer.
We discuss below each of
these Computer operation
1. Input: This is the process of entering data and programs in to the
computer system. You should know that computer is an electronic machine like
any other machine which takes as inputs raw data and performs some processing
giving out processed data. Therefore, the input unit takes data from us to the
computer in an organized manner for processing.
2. Storage: The process of saving data and instructions permanently is known
as storage. Data has to be fed into the system before the actual processing
starts. It is because the processing speed of Central Processing Unit (CPU) is
so fast that the data has to be provided to CPU with the same speed. Therefore
the data is first stored in the storage unit for faster access and processing.
This storage unit or the primary storage of the computer system is designed to
do the above functionality. It provides space for storing data and
instructions.
The storage unit
performs the following major functions:
• All data and
instructions are stored here before and after processing.
• Intermediate results
of processing are also stored here.
3. Processing: The task of performing operations like arithmetic and logical
operations is called processing. The Central Processing Unit (CPU) takes data
and instructions from the storage unit and makes all sorts of calculations
based on the instructions given and the type of data provided. It is then sent
back to the storage unit.
4. Output: This is the process of producing results from the data for getting
useful information.
Similarly the output produced by the computer after processing must also be
kept somewhere inside the computer before being given to you in human readable
form. Again the output is also stored inside the computer for further
processing.
5. Control: The manner how instructions are executed and the above operations
are performed. Controlling of all operations like input, processing and output
are performed by control unit.
It takes care of step by step processing of all operations inside the computer.
FUNCTIONAL
UNITS
In order to carry out
the operations mentioned in the previous section the computer allocates the
task between its various functional units. The computer system is divided into
three separate units for its operation. They are
Arithmetic
Logical Unit (ALU)
Logical Unit :After you enter data through the input device it is stored
in the primary
storage unit. The actual processing of the data and instruction are
performed by Arithmetic Logical Unit. The major operations performed by the ALU
are addition, subtraction, multiplication, division, logic and comparison. Data
is transferred to ALU from storage unit when required. After processing the
output is returned back to storage unit for further processing or getting
stored.
Control
Unit (CU)
The next component of
computer is the Control Unit, which acts like the supervisor seeing that things
are done in proper fashion. Control Unit is responsible for co
ordinating various operations using time signal. The control unit determines
the sequence in which computer programs and instructions are executed. Things
like processing of programs stored in the main memory, interpretation of the
instructions and issuing of signals for other units of the computer to execute
them. It also acts as a switch board operator when several users access the
computer simultaneously. Thereby it coordinates the activities of computer’s
peripheral equipment as they perform the input and output.
Central
Processing Unit (CPU)
The ALU and the CU of a
computer system are jointly known as the central
processing unit. You may call CPU as the brain of any computer
system. It is just like brain that takes all major decisions, makes all sorts
of calculations and directs different parts of the computer functions by
activating and controlling the operations.
Computers differ based
on their data processing abilities. They are classified according to purpose,
data handling and functionality.
According to purpose,
computers are either general purpose or specific purpose. General
purpose computers are designed to perform a range of tasks. They
have the ability to store numerous programs, but lack in speed and efficiency.
Specific purpose computers are designed to handle a specific problem or to
perform a specific task. A set of instructions is built into the machine.
According to data handling,
computers are analog, digital or hybrid. Analog computers work on the principle
of measuring, in which the measurements obtained are translated into data.
Modern analog computers usually employ electrical parameters, such as voltages,
resistances or currents, to represent the quantities being manipulated. Such
computers do not deal directly with the numbers. They measure continuous
physical magnitudes. Digital computers are those that operate with information,
numerical or otherwise, represented in a digital form. Such computers process
data into a digital value (in 0s and 1s). They give the results with more
accuracy and at a faster rate. Hybrid
computers incorporate the measuring feature of an analog computer and counting feature of a digital
computer. For computational purposes, these computers use analog
components and for storage, digital memories are used.
According to
functionality, Type of computers are classified as :
Analog
Computer
An analog computer
(spelt analogue in British English) is a form of computer that uses continuous physical
phenomena such as electrical, mechanical, or hydraulic quantities to model the
problem being solved.
Digital
Computer
A computer that
performs calculations and logical operations with quantities represented as
digits, usually in the binary
number system
Hybrid
Computer (Analog + Digital)
A combination of
computers those are capable of inputting and outputting in both digital
and analog
signals. A hybrid computer system setup offers a cost effective
method of performing complex simulations.
On the basis of
Size: Type of Computer
Super
Computer
The fastest and most
powerful type of computer Supercomputers are very expensive and are employed
for specialized applications that require immense amounts of mathematical
calculations. For example, weather forecasting requires a supercomputer.
Other uses of supercomputers include animated graphics, fluid dynamic
calculations, nuclear energy research, and petroleum exploration.
The chief difference
between a supercomputer and a mainframe is
that a supercomputer channels all its power into executing a few programs as
fast as possible, whereas a mainframe uses its power to execute many programs
concurrently.
Mainframe
Computer
A very large and
expensive computer capable of supporting hundreds, or even thousands, of users
simultaneously. In the hierarchy that starts with a simple microprocessor (in
watches, for example) at the bottom and moves to supercomputers at the top,
mainframes are just below supercomputers. In some ways, mainframes are more
powerful than supercomputers because they support more simultaneous programs.
But supercomputers can execute a single program faster than a mainframe.
Mini
Computer
A midsized computer. In
size and power, minicomputers lie between workstations and mainframes.
In the past decade, the distinction between large minicomputers and small
mainframes has blurred, however, as has the distinction between small
minicomputers and workstations. But in general, a minicomputer is a multiprocessing
system capable of supporting from 4 to about 200 users simultaneously.
Micro
Computer or Personal Computer
• Desktop
Computer: a personal or micro-mini computer sufficient to fit on a desk.
• Laptop
Computer: a portable computer complete with an integrated screen and
keyboard. It is generally smaller in size than a desktop computer and larger
than a notebook computer.
• Palmtop
Computer/Digital Diary /Notebook /PDAs: a hand-sized computer. Palmtops
have no keyboard but the screen serves both as an input and output device.
Workstations
A terminal or desktop
computer in a network. In this context, workstation is just a generic term for
a user's machine (client machine) in contrast to a "server" or
"mainframe."
Basic
characteristics about computer are:
1. Speed: - As you know computer can work very fast. It takes only few seconds
for calculations that we take hours to complete. You will be surprised to know
that computer can perform millions (1,000,000) of instructions and even more
per second.
Therefore, we determine
the speed of computer in terms of microsecond (10-6 part of a second) or
nanosecond (10 to the power -9 part of a second). From this you can imagine how
fast your computer performs work.
2. Accuracy: - The degree of accuracy of computer is very high and every calculation
is performed with the same accuracy. The accuracy level is 7.
determined on the basis
of design of computer. The errors in computer are due to human and inaccurate
data.
3. Diligence: - A computer is free from tiredness, lack of concentration, fatigue,
etc. It can work for hours without creating any error. If millions of
calculations are to be performed, a computer will perform every calculation
with the same accuracy. Due to this capability it overpowers human being in
routine type of work.
4. Versatility: - It means the capacity to perform completely different type of
work. You may use your computer to prepare payroll slips. Next moment you may
use it for inventory management or to prepare electric bills.
5. Power of Remembering:
- Computer has the power
of storing any amount of information or
data. Any information can be stored and recalled as long as you require it, for
any numbers of years. It depends entirely upon you how much data you want to
store in a computer and when to lose or retrieve these data.
6. No IQ: - Computer is a dumb machine and
it cannot do any work without instruction from the user. It performs the
instructions at tremendous speed and with accuracy. It is you to decide what
you want to do and in what sequence. So a computer cannot take its own decision
as you can.
7. No Feeling: - It does not have feelings or emotion, taste, knowledge and
experience. Thus it does not get tired even after long hours of work. It does
not distinguish between users.
8. Storage: - The Computer has an in-built memory where it can store a large
amount of data. You can also store data in secondary storage devices such as floppies, which
can be kept outside your computer and can be carried to other computers.
Each generation of computer is
characterized by a major technological development that fundamentally changed
the way computers operate, resulting in increasingly smaller, cheaper, more
powerful and more efficient and reliable devices.
The various generations
of computers an listed below :
(i) First Generation
(1946-1954) : In 1946 there
was no 'best' way of storing instructions and data in a computer memory. There
were four competing technologies for providing computer memory: electrostatic
storage tubes, acoustic delay lines (mercury or nickel), magnetic
drums (and disks?), and magnetic core storage.
The digital computes
using electronic valves (Vacuum tubes) are known as first
generation computers. the first 'computer' to use electronic valves (ie. vacuum
tubes). The high cost of vacuum tubes prevented their use for main memory. They
stored information in the form of
propagating sound waves.
The vacuum tube consumes
a lot of power. The Vacuum tube was developed by Lee DeForest in 1908. These
computers were large in size and writing programs on them was difficult. Some
of the computers of this generation were:
Mark I : The IBM Automatic Sequence Controlled Calculator (ASCC),
called the Mark I by Harvard University, was an electro-mechanical
computer. Mark I is the first machine to successfully perform a long
services of arithmetic and logical operation. Mark I is the First
Generation Computer. it was the first operating machine that could execute
long computations automatically. Mark I computer
which was built as a partnership between Harvard and IBM in 1944.
This was the first programmable digital computer made in the U.S. But
it was not a purely electronic computer. Instead the Mark I was constructed out
of switches, relays, rotating shafts, and clutches. The machine weighed 5 tons,
incorporated 500 miles of wire, was 8 feet tall and 51 feet long, and had a 50
ft rotating shaft running its length, turned by a 5 horsepower electric motor.
ENIAC: It was the first general-purpose electronic computer built
in 1946 at University of Pennsylvania, USA by John
Mauchly and J. Presper Eckert. The completed machine was announced to the
public the evening of February 14, 1946. It was named Electronic
Numerical Integrator and Calculator (ENIAC). ENIAC contained 17,468
vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000
capacitors and around 5 million hand-soldered joints. It weighed more than 30
short tons (27 t), was roughly 8 by 3 by 100 feet (2.4 m × 0.9 m × 30 m), took
up 1800 square feet (167 m2), and consumed 150 kW of power. Input was possible
from an IBM card reader, and an IBM card punch was
used for output. These cards could be used to produce printed output offline
using an IBM accounting machine, such as the IBM 405. Today your
favorite computer is many times as powerful as ENIAC, still size is very
small.
EDVAC: It stands for Electronic Discrete Variable Automatic
Computer and was developed in 1950.it was to be a vast
improvement upon ENIAC, it was binary rather than decimal,
and was a stored program computer. The concept of storing data and
instructions inside the computer was introduced here. This allowed
much faster operation since the computer had rapid access to both data and
instructions. The other advantage of storing instruction was that computer
could do logical decision internally.
The EDVAC was a binary
serial computer with automatic addition, subtraction, multiplication,
programmed division and automatic checking with an ultrasonic serial memory.
EDVAC's addition time was 864 microseconds and its multiplication
time was 2900 microseconds (2.9 milliseconds).
The computer had almost
6,000 vacuum tubes and 12,000 diodes, and consumed 56 kW of power. It covered
490 ft² (45.5 m²) of floor space and weighed 17,300 lb (7,850 kg).
EDSAC: It stands for Electronic Delay Storage Automatic Computer and
was developed by M.V. Wilkes at Cambridge University in 1949. Two
groups of individuals were working at the same time to develop the first
stored-program computer. In the United States, at the University of
Pennsylvania the EDVAC (Electronic Discrete Variable Automatic Computer) was
being worked on. In England at Cambridge, the EDSAC (Electronic Delay Storage
Automatic Computer) was also being developed. The EDSAC won
the race as the first stored-program computerbeating the United
States’ EDVAC by two months. The EDSAC performed computations in the three
millisecond range. It performed arithmetic and logical operations without human
intervention. The key to the success was in the stored instructions which
it depended upon solely for its operation. This machine marked the
beginning of the computer age. EDSAC is the first computer is used to
store a program
UNIVAC-1: Ecker and Mauchly produced it in 1951 by Universal
Accounting Computer setup. it was the first commercial
computer produced in the United States. It was designed principally by
J. Presper Eckert and John Mauchly, the inventors of the ENIAC.
The machine was 25 feet
by 50 feet in length, contained 5,600 tubes, 18,000 crystal diodes, and 300
relays. It utilized serial circuitry, 2.25 MHz bit rate, and had an internal
storage capacity 1,000 words or 12,000 characters.
It utilized a Mercury
delay line, magnetic tape, and typewriter output. The UNIVAC
was used for general purpose computing with large amounts of
input and output.
Power consumption was
about 120 kva. Its reported processing speed was 0.525 milliseconds for
arithmetic functions, 2.15 milliseconds for multiplication and 3.9 Milliseconds
for division.
The UNIVAC was also the
first computer to come equipped with a magnetic tape unit and was the first
computer to use buffer memory.
Other Important
Computers of First Generation
Some other computers of
this time worth mentioning are the Whirlwind, developed at Massachussets
Institute of Technology, and JOHNNIAC, by the Rand Corporation. The Whirlwind
was the first computer to display real time video and use core memory. The
JOHNNIAC was named in honor of Jon Von Neumann. Computers at this time were
usually kept in special locations like government and university research labs
or military compounds.
Limitations of First
Generation Computer
Followings are the major
drawbacks of First generation computers.
1. They used
valves or vacuum tubes as their main electronic component.
2. They were large in
size, slow in processing and had less storage capacity.
3. They consumed
lots of electricity and produced lots of heat.
4. Their computing
capabilities were limited.
5. They were not so
accurate and reliable.
6. They used
machine level language for programming.
7. They were very
expensive.
Example: ENIAC, UNIVAC,
IBM 650 etc
(ii) Second
Generation (1955-1964) : The second-generation computer used transistors for
CPU components & ferrite cores for main memory & magnetic
disks for secondary memory. They used high-level languages such
as FORTRAN (1956), ALGOL (1960) & COBOL (1960 - 1961). I/O
processor was included to control I/O operations.
Around 1955 a device
called Transistor replaced the bulky Vacuum tubes in
the first generation computer. Transistors are smaller than Vacuum tubes and
have higher operating speed. They have no filament and require no heating.
Manufacturing cost was also very low. Thus the size of the computer got reduced
considerably.
It is in the second
generation that the concept of Central Processing Unit (CPU), memory,
programming language and input and output units were developed. The programming
languages such as COBOL, FORTRAN were developed during this period. Some of the
computers of the Second Generation
were
1. IBM 1620:
Its size was smaller as compared to First Generation computers and mostly used
for scientific purpose.
2. IBM 1401:
Its size was small to medium and used for business applications.
3. CDC 3600:
Its size was large and is used for scientific purposes.
Features:
1. Transistors
were used instead of Vacuum Tube.
2. Processing
speed is faster than First Generation Computers (Micro Second)
3. Smaller in Size
(51 square feet)
4. The input and output devices
were faster.
Example: IBM 1400 and
7000 Series, Control Data 3600 etc.
(iii) Third
Generation (1964-1977) : By the development of a small chip consisting
of the capacity of the 300 transistors. These ICs are popularly
known as Chips. A single IC has many transistors, registers and
capacitors built on a single thin slice of silicon. So it is quite
obvious that the size of the computer got further reduced. Some of the
computers developed during this period were IBM-360, ICL-1900, IBM-370,
and VAX-750. Higher level language such as BASIC (Beginners All
purpose Symbolic Instruction Code) was developed during this
period. Computers of this generation were small in size, low cost, large
memory and processing speed is very high. Very soon ICs Were replaced by LSI
(Large Scale Integration), which consisted about 100 components. An IC
containing about 100 components is called LSI.
Features:
1. They used Integrated
Circuit (IC) chips in place of the transistors.
2. Semi conductor memory
devices were used.
3. The size was
greatly reduced, the speed of processing was high, they were more
accurate and reliable.
4. Large Scale
Integration (LSI) and Very Large Scale Integration (VLSI) were also developed.
5. The mini
computers were introduced in this generation.
6. They used high level
language for programming.
Example: IBM 360, IBM
370 etc.
(iv) Fourth
Generation : An IC containing about 100 components is called LSI
(Large Scale Integration) and the one, which has more than 1000 such
components, is called as VLSI (Very Large Scale Integration). It
uses large scale Integrated Circuits (LSIC) built on a single
silicon chip called microprocessors. Due to the development of microprocessor it is possible to
place computer’s central processing unit (CPU)
on single chip. These computers are called microcomputers. Later very
large scale Integrated Circuits (VLSIC) replaced LSICs. Thus the
computer which was occupying a very large room in earlier days can now be
placed on a table. The personal
computer (PC) that you see in your school is a Fourth
Generation Computer Main memory used fast semiconductors chips up to 4 M bits
size. Hard disks were used as secondary memory. Keyboards, dot matrix printers
etc. were developed. OS-such as MS-DOS, UNIX, Apple’s Macintosh were
available. Object oriented language, C++ etc were developed.
Features:
1. They used
Microprocessor (VLSI) as their main switching element.
2. They are also called
as micro computers or personal computers.
3. Their size varies
from desktop to laptop or palmtop.
4. They have very
high speed of processing; they are 100% accurate, reliable,
diligent and versatile.
5. They have very
large storage capacity.
Example: IBM PC,
Apple-Macintosh etc.
(v) Fifth
Generation (1991- continued) : 5th generation computers use ULSI
(Ultra-Large Scale Integration) chips. Millions of transistors are placed in a
single IC in ULSI chips. 64 bit microprocessors have been developed during this
period. Data flow & EPIC architecture of these processors have been
developed. RISC & CISC, both types of designs are used in modern
processors. Memory chips and flash memory up to 1 GB, hard disks up to 600 GB
& optical disks up to 50 GB have been developed. fifth generation digital
computer will be Artificial intelligence.
What is CPU: It's meaning is Central Processing Unit.
Sometimes referred to simply as the central processor or Nerve
Centre or heart, but more commonly called processor,
the CPU is where most calculations take place. The CPU is the brains
of the computer.
CPU
Definition
Central processing unit
(CPU) is the central component of the Computer System. Sometimes it is called
as microprocessor or
processor. It is the brain that runs the show inside the Computer.
All functions and processes that is done on a computer is performed
directly or indirectly by the processor. Obviously, computer processor is
one of the most important element of the Computer system. CPU is
consist of transistors,that receives inputs and produces output.Transistors
perform logical operations which is called processing. It is also,
scientifically, not only one of the most amazing parts of the PC, but one of
the most amazing devices in the world of technology.
In terms of computing
power, the computer processor is the most important element of
a computer system. It add and compare its data in cpu chip. A CPU of all
computers, whether micro, mini or mainframe must
have three parts.
Parts
of CPU
Arithmetic Logic Unit (ALU): It is the part of computer processor (CPU) can
be used to perform arithmetic and logic operations. An arithmetic-logic unit
(ALU) is further divided into two parts, (AU) arithmetic unit and a (LU)
logic unit.
Control Unit (CU): Decodes the program
instruction. CPU chip used in a computer is partially made out of Silica. on
other words silicon chip used for data processing are called Micro
Processor.
Registers: It is temporary storage areas of the computer processor. It is
managed by control unit(CU).Registers
holding data,instruction and address that are needed by program while running.
The processor plays a
significant role in the following important aspects of your computer system;
Performance: The processor is probably the most important single
determinant of system performance in the Pc. While other components also playa
key role in determining performance, the processor's capabilities dictate the
maximum performance of a system. The other devices only allow the processor to
reach its full potential.
Software Support: Newer, faster processors enable the use of the latest
software. In addition, new processors such as the Pentium with MMX Technology,
enable the use of specialized software not usable on earlier machines.
Reliability and
Stability: The quality of the
processor is one factor that determines how reliably your system will run.
While most processors are very dependable, some are not. This also depends to
some extent on the age of the processor and how much energy it consumes.
Energy Consumption and
Cooling: Originally
processors consumed relatively little power compared to other system devices.
Newer processors can consume a great deal of power. Power consumption has an
impact on everything from cooling method selection to overall system
reliability.
Motherboard Support: The processor that decides to use in your system will be a
major determining factor in what sort of chipset we must use, and hence what
motherboard you buy. The motherboard in turn dictates many facets of. The
system's capabilities and performance.
Von Neumann
Architecture also known as the Von Neumann model,
the computer consisted
of a CPU, memory and I/O devices. The program is stored in the memory. The CPU
fetches an instruction from the memory at a time and executes it.
Thus, the instructions
are executed sequentially which is a slow process. Neumann m/c are called
control flow computer because instruction are executed sequentially as
controlled by a program counter. To increase the speed, parallel processing of
computer have been developed in which serial CPU’s are connected in parallel to
solve a problem. Even in parallel computers, the basic building blocks are
Neumann processors.
The von Neumann
architecture is a design model for a stored-program digital computer that uses a
processing unit and a single separate storage structure to hold both
instructions and data. It is named after mathematician and early computer
scientist John von Neumann. Such a computer implements a universal Turing
machine, and the common "referential model" of specifying sequential
architectures, in contrast with parallel architectures.
One shared memory for
instructions (program) and data with one data bus and one address bus between
processor and memory. Instructions and data have to be fetched in sequential
order (known as the Von Neuman Bottleneck), limiting the operation bandwidth.
Its design is simpler than that of the Harvard architecture. It is mostly used
to interface to external memory.
A BIOS (Basic
Input/Output System) Short for ROM is boot
firmware program that a computer uses to successfully start
operating. The BIOS is
located on a chip inside of the computer and is designed in a way that protects
it from disk failure.
When
you turn on a PC, the BIOS first conduct a basic hardware check, called a
Power-On Self Test (POST), to determine whether all of the attachments are
present and working. Then it loads the operating system into your computer's
random access memory, or RAM. The BIOS also manages data flow between the
computer's operating system and attached devices such as the hard disk, video
card, keyboard, mouse, and printer. The BIOS stores the date, the time,
and your system configuration information in
a battery-powered, non-volatile memory chip, called a CMOS (Complementary Metal
Oxide Semiconductor) after its manufacturing process. The main functions of the
BIOS are:
Functions
of BIOS
(i) BIOS Power on
Self Test (POST): It is a
built-in diagnostic program. This self test ensures that the computer has all
of the necessary parts and functionality needed to successfully start itself,
such as use of memory, a keyboard and other parts. Then additional tests are
done during booting. If errors are detected during the test, the BIOS instruct
the computer to give a code that reveals the problem. Error codes are typically
a series of beeps heard shortly after startup.
The BIOS also works to
give the computer basic information about how to interact with some critical
components, such as drives and memory that it will need to load the operating
system. Once the basic instructions have been loaded and the self-test has been
passed, the computer can proceed with loading the operating system from one of
the attached drives. Computer users can often make certain adjustments to the
BIOS through a configuration screen on the computer. The setup screen is
typically accessed with a special key sequence during the first moments of
startup. This setup screen often allows users to change the order in which
drives are accessed during startup and control the functionality of a number of
critical devices. Features vary among individual BIOS versions.
We can also use
flash-memory cards to hold BIOS information. This allows users to update the
BIOS version on computers after a vendor releases an update. This system was
designed to solve problems with the original BIOS or to add new functionality.
Users can periodically check for updated BIOS versions, as some vendors release
a dozen or more updates over the course of a product's lifetime. Mother board
(System) BIOS, Video adapter firmware (BIOS), Drive controller firmware (BIOS),
Modem Card firmware (BIOS), Network adapter board BIOS, SCSI adapter BIOS. The
mother board BIOS provides routines to support motherboard features. BIOS ROM
chips for major sub systems of computer such as video and drive control must
also be included.
Actually BIOS can be
placed in between the computer and external devices as its name tells it is
used for reading the keystroke, displaying values on screen, Reading and
writing to and from floppy and hard disks etc.
The keyboard is assigned
the port number 60, which is known to BIOS. BIOS read this port and data from
keyboard goes to computer.
(ii) Bootstrap
Loader: To boot the operating system. The BIOS contains a program known as
bootstrap loader whose responsibility is to search and start the operating
system boot program. Then the boot program of operating system controls the
computer system and boots the operating system.
(iii) BIOS Setup Utility
Program: A non volatile memory
(NVRAM) is used to store information about the computer system. During
installation of a system, the user run BIOS setup program and enter the correct
parameters. The settings of memory, disk types and other settings are stored in
NVRAM and not in BIOS chip itself. To construct NVRAM, the material required is
CMOS (Complementary metal oxide semiconductor).
These CMOS chips are very efficient storage devices as they store and
maintain data on very low values of current. The system's configurations
therefore are also termed as CMOS settings, which we can set using BIOS set up
program. The BIOS reads the parameters from CMOS RAM as and when required.
CMOS settings can be
maintained by battery backup either by using capacitor or by a battery built
into NVRAM chip. This chip also has system clock. If there is no battery, the
setting remains for short period of time and we need to reset the system. With
it there is loss of BIOS password which protects BIOS set up program.
To clear the CMOS RAM
contents, two methods used are
(i) By using clear CMOS jumper.
(ii) By holding down enter key during booting of the system.
For Pentium III
motherboards, different set ups are there in AMI BIOS. These are:
• Standard CMOS Setup:It is used to set time date, hard disk type, type of floppy drive,
type of monitor and keyboard.
Advanced CMOS Setup:It is used to set typematic rate and delay, above 1 MB memory
test, memory test tick sound, Hil < Del> message display, system boot up
sequence etc.
• Advanced Chipset
Setup:It is used to set
features of chipset.
• Power Management
Setup:It is used to control
power conservation options.
• PCI/Plug and Play
Setup:It is used to set
options of PCI bus and that of plug and play devices.
• Peripherals Setup:It is used to control options related to I/O controllers.
• CPU Configuration
Setup:This setup is used to
select the types of CPU installed in the motherboard. In AMI BIOS, the settings
are auto as it automatically finds out the type of CPU in the computer
system.
(iv) System Service Routines: The BIOS provides various software routines (subprograms) that can
be called by higher-level software such, as DOS, Windows, or their
applications, to perform different tasks. Virtually every task that involves
accessing the system hardware has traditionally been controlled using one or
more of the BIOS programs (although many newer operating systems now bypass the
BIOS for improved performance). This includes actions like reading and writing
from the hard disk, processing information received from devices, etc.
BIOS services are
accessed using software interrupts, which are similar to the hardware
interrupts except that they are generated inside the processor by programs
instead of being generated outside the processor by hardware devices. One thing
that this use of interrupts does is to allow access to the BIOS without knowing
where in memory each routine is located.
Normally, to call a
software routine you need to know its address. With interrupts, a table called
an interrupt vector table is used that bypasses this problem.
When the system is started up, the BIOS puts addresses into this table that
represent where its routines are located for each interrupt it responds to.
Then, when DOS or an application wants to use a BIOS routine, it generates a
software interrupt. The system processes the interrupt, looks up the value in
the table, and jumps to the BIOS routine automatically. DOS itself and
application programs can also use this interrupt vector table.
DMA stands
for "Direct
Memory Access" and is a method of transferring data from
the computer's RAM to another part of the computer
without processing it using the CPU. While most data that is input or output
from your computer is processed by the CPU, some data does not require
processing, or can be processed by another device.
In these situations, DMA
can save processing time and is a more efficient way to move data from the
computer's memory to other devices. In order for
devices to use direct memory access, they must be assigned to a DMA channel.
Each type of port on a computer has a set of DMA channels that can be assigned
to each connected device. For example, a PCI controller and a hard drive
controller each have their own set of DMA channels.
For example, a sound
card may need to access data stored in the computer's RAM, but since it can
process the data itself, it may use DMA to bypass the CPU. Video cards that
support DMA can also access the system memory and process graphics without
needing the CPU. Ultra DMA hard drives use DMA to transfer data faster than
previous hard drives that required the data to first be run through the
CPU.
An alternative to DMA is
the Programmed Input/Output (PIO) interface in which all data transmitted
between devices goes through the processor. A newer protocol for
the ATAIIDE interface is Ultra DMA, which provides a burst data transfer rate
up to 33 mbps. Hard drives that come with Ultra DMAl33 also support PIO modes
1, 3, and 4, and multiword DMA mode 2 at 16.6 mbps.
DMA
Transfer Types
Memory
To Memory Transfer
In this mode block of
data from one memory address is moved to another memory address. In this mode
current address register of channel 0 is used to point
the source address and the current address register of channel is used to point
the destination address in the first transfer cycle, data byte from the source
address is loaded in the temporary register of the DMA controller and in the
next transfer cycle the data from the temporary register is stored in the
memory pointed by destination address. After each data transfer current
address registers are decremented or incremented
according to current settings. The channel 1 current word count register is
also decremented by 1 after each data transfer. When the word count of channel
1 goes to FFFFH, a TC is generated which activates EOP output terminating the
DMA service.
Auto
initialize
In this mode, during the
initialization the base address and word count registers are loaded
simultaneously with the current address and word count registers by the microprocessor.
The address and the count in the base registers remain unchanged throughout the
DMA service.
After the first block
transfer i.e. after the activation of the EOP signal, the original values of
the current address and current word count registers are automatically restored
from the base address and base word count register of that channel. After auto
initialization the channel is ready to perform another DMA service, without CPU
intervention.
DMA
Controller
The controller is integrated into the processor board and manages all
DMA data transfers. Transferring data between system memory and an 110 device
requires two steps. Data goes from the sending device to the DMA controller and
then to the receiving device. The microprocessor gives the DMA controller the
location, destination, and amount of data that is to be transferred. Then the
DMA controller transfers the data, allowing the microprocessor to continue with
other processing tasks. When a device needs to use the Micro Channel bus to
send or receive data, it competes with all the other devices that are trying to
gain control of the bus. This process is known as arbitration. The DMA
controller does not arbitrate for control of the BUS instead; the I/O device
that is sending or receiving data (the DMA slave) participates in arbitration.
It is the DMA controller, however, that takes control of the bus when the
central arbitration control point grants the DMA slave's request.
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