Wednesday, 21 December 2016
Tuesday, 9 February 2016
COM111 Lecture Schedule 2
COM111 Lecture Schedule 2
The Computer
System, Computer Organization and Architecture, Central Processing Unit, Inside
a Computer
Computer
System
Every computer needs to be
instructed exactly what to do and how to do. The instructions given to
computers are called as programs. The parts of the computers are classified into
two major categories such as hardware (All
Physical parts) and software (All
information or data).
Hardware:
The physical parts that make up a computer (CPU, input, output and
storage) are known as hardware. Any hardware device connected to the computer
or any part of the computer outside the CPU and working memory is known as
peripheral. Examples of peripherals are keyboards, mouse and monitors.
Software:
The user issues
instructions and the CPU acts in accordance with the instructions. The sets of
instructions, which control the sequence of operations, are known as programs,
and collectively programs are called software.
Computer Organization and
Architecture
A computer is
designed using four basic units:
· Central
Processing Unit
· Input
Unit
· Output
Unit
· Storage/Memory
Unit
Central Processing
Unit (CPU):
The CPU, is also known as a
processor, is the brain of the computer system that processes data (input) and
converts it into meaningful information (output). It is referred to as the
administrative section of the computer system. CPU works with data in discrete
form that is either 1 or 0. In addition, it contro0ls the usage of the main
memory to store data and instructions, and controls the sequence of operations.
The CPU itself has three subsystems, The i)arithmetic /logic unit ii)the
control unit and iii)the registers. The three subsystems work together to
provide operational capabilities to a computer.
Arithmetic/logic Unit
(ALU):
Arithmetic/logic Unit (ALU) contains the electronic circuitry that executes and
performs all the arithmetic(add, subtract) and logical operations(and, or) on
the data made available to it. ALU comprises of two units: Arithmetic Unit(AU)
and Logic Unit(LU).
Arithmetic Unit(AU):
The AU contains the circuitry that is responsible for performing the actual
computing and carrying out arithmetic calculations such as addition ,
subtraction, Multiplication and Division. It can perform these operations at a
very high speed.
Logic Unit(LU): The
LU enables the CPU to make logical operations based on the instructions
provided to it. These operations are logical comparisons between data items.
The LU can compare numbers, letters or special characters and then take action
based on the result of the comparison. Logical operations of the LU test for
three conditions:
·
Equal-to condition: In a test for this condition, the ALU compares
two values to determine if they are equal.
·
Less than condition: To test this condition ,the ALU compares two
values to determine if one is less than the other.
·
Greater than condition: To test this condition the ALU compares two values to determine if
one is greater than the other.
Control Unit: This unit checks the
correctness of the sequence of operations. It also controls the I/O devices and
directs the overall functioning of the other units of the computer.
Registers: These are the
special-purpose, high-speed temporary memory units that can hold varied
information such as data, instructions, addresses and intermediate results of
calculations. The registers can be considered as the CPU’s working memory, an
additional storage location that provides the advantage of speed.
INPUT UNIT:
An input unit accepts instructions
and data from the user with help of input devices such as keyboard, mouse,
light pen etc. The input unit converts the data and instructions into the form
that the computer can understand. After this, the input unit supplies the
converted instructions and data to the computer for further processing.
OUTPUT UNIT:
The output unit performs just
opposite to that of input unit. It accepts the output(which is in machine coded
form)produced by the computer, converts them into the user understandable form
and supplies the converted results to the user with the help of an output
device.
STORAGE/MEMORY UNIT:
The storage unit of a computer
comprises two types of memory/storage. They are primary memory and secondary
memory.
Primary Memory:
The primary memory, also called the
main memory, is the part of a computer holds the instructions and data
currently being processed by the CPU, the intermediate results produces during
the course of calculations and the recently processed data. While the
instructions and data remain in the main memory, the CPU can access them
directly and quickly. However, the primary memory is quite expensive and has a
limited storage capacity.
Secondary Memory:
Due to the limited size of the
primary memory, a computer employs the secondary memory, which is extensively
used for storing data and instructions. It is less expensive and has higher
storage capacity than the primary memory. Some commonly used secondary storage
devices are floppy disk, hard disks and tape drives.
Input/output Devices
The user interacts with the computer via I/O
unit. The Input unit accepts data from the user and the Output unit provides
the processed data i.e. the information to the user.
Input Devices
Input device is a hardware device that sends
information to the computer.
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Mouse:
Mouse is a pointer device. The mouse allows
an individual to control a pointer in
a graphical user interface (GUI). Utilizing
a mouse a user has the ability to per-form various functions such as opening
a program or file and does not require the user to memorize commands.
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Digital camera:
A type of camera that stores the pictures
or video it takes in electronic format instead of to film.
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Web Cam:
A camera connected to a computer that allows
anyone connected to the Internet to view still pictures or motion video of a
user.
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Joystick:
A computer joystick allows an individual to
easily navigate an object in a game such as navigating a plane in a flight
simulator.
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Keyboard:
One of the main input devices used on a
computer, a computer keyboard looks very similar to the keyboards of electric
typewriters, with some additional keys.. QWERTY, AZERTY, Dvorak are the different
types of keyboards.
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Microphone
Sometimes abbreviated as mic, a microphone
is a hardware peripheral that allows computer users to input audio into their
computers.
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Scanner
Input device that allows a
user to take an image and/or text and convert it into a digital file,
allowing the computer to read and/or display the scanned object
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Output Device
Any peripheral that receives and/or displays output from
a computer. Below are some examples of different types of output devices
commonly found on a computer.
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Monitor
A
monitor is a video display screen. Monitor is also called as Visual Display
Unit (VDU) or Video Display Terminal (VDT). CRT (Cathode Ray Tube), LCD
(Liquid Crystal Display), LED (Light Emitting Diodes), TFT-LCD (Thin Film
Technology LCD) are the different types of displays.
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CRT (Cathode Ray Tube)
Monitors are built very similarly to older (tube) television
sets. They are heavy, bulky, take up a lot of desk space, and emit radiation.
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LCD (Liquid Crystal Display)
Monitors are thin and flat. They are light, compact, take up
very little desk space emit no known radiation.
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Printer
A printer is an output device responsible for taking computer
data and generating a hard copy of that data. Inkjet printers, Laser
printers, dot matrix are the different types of the printers.
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Projector
Take the display of a computer screen and project a large
version of it onto a flat surface.
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Speakers
Connected to a computer’s sound card that outputs sounds
generated by the computer.
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How
does a Computer Work?
A Computer can perform three basic
steps to complete any task: input, processing and output. A task is
assigned to a computer in a set of step-by-step instructions, which is known as
a program. A computer functions in the following manner:
STEP:1
The Computer accepts
the input. The computer input is whatever entered or fed into a computer system
. Some examples of input include the words and symbols in a document, numbers
for a calculation, instructions for completing a process and so on.
STEP:2
The computer processes the data.
During this stage, the computer follows the instructions using the data that
have been input. Examples of processing include calculations, sorting lists of
words or numbers and so on.
STEP:3
The computer produces output.
Computer output is the information that has been produced by a computer. Some
examples of Computer output includes reports, documents, graphs and so on.
Inside a Computer:
Computing machines
are complex devices made from numerous electronic devices made from numerous
electronic components. Many of these components are small, sensitive, and
expensive and operate with other components to provide better performance to
the computing machines. Therefore, to ensure better performance and increase in
the life of these components, they are placed inside a metal enclosure called
the system case or cabinet. The system case is a metal plastic box that houses
the main components of the computer. It protects the electronic hardware
against the heat, light, temperature etc. Roles of system case are:
Structure: The system
case provides rigid structure to the components.
Protection: The
system case protects the inside of the system from physical damage and
electrical interface.
Cooling: The system
case provides a cooling system to the vital components.
Organization and
Expandability: The system case is a key to the organization of physical
systems. If a system case is poorly designed, up gradation or expansion of a
peripheral is limited.
Status Display: The
system case contains lights or LEDs that provide varied information pertaining
to the working of the system to the user. The system case encloses all the
components including the motherboard, processors, memory, power supply,
expansion slots, cables, removable drives etc.,
Power Supply(SMPS):
Power Supply or switch-mode power supply is a transformer and voltage control
device that converts incoming AC to DC and then supplies DC to all the
components of the computer.
Motherboard:
Motherboard also known as system board, is a large multilayered printed circuit
board inside a computer. The motherboard contains CPU, BIOS ROM chip, RAM slots
and underlying circuitry the CMOS.
BIOS: The BIOS
comprises of startup instructions inside the ROM.
CMOS: The motherboard
includes a separate block of memory called the Complementary Metal-oxide
silicon chip that consumes very low power. This chip is kept alive by a battery
even when the computer’s power is off. The most important data which is kept in
the CMOS battery is the system time and date.
Storage Devices: Disk
drives are the important components present inside the system case. These
drives are used to read and write information to and from the processors. The
three common diskdrives located inside a system case are the hard drive, floppy
drive and CD-ROM.
Processors: The
Processors often called as the CPU is the central component of the computer. It
is referred to brain of the Computer responsible for carrying out operations in
an efficient and effective manner.
COM111 Lecture Schedule 1
COM111 Lecture Schedule 1
Introduction
to Computer, Evolution of Computers, Generation of Computers and Classification
of Computers
Introduction
to Computers
In
the beginning of the civilization, people used fingers and pebbles for
computing purposes. The word digitus in Latin actually means finger and
calculus means pebble. The need for a mechanism to perform lengthy calculations
led to the invention of, first, calculator and then computers. Since the
computer covers a huge area of application this era is called as information
age.
What
is a computer?
·
An
electronic device for processing and storing information.
·
A
computer is a programmable machine.
·
The
two principal characteristics of a computer are: it responds to a specific set
of instructions in a well-defined manner and it can execute a prerecorded list
of instructions (a program).
·
Does
not create information. Cannot think (unlike brain).
The main characteristics of computers are:
a) Speed :
Computers process data at an extremely fast rate, at
millions or billions of instructions per second. The speed of a computer is
calculated in MHz i.e 1 million instructions per second. At present the
powerful computer can perform billions of operations in just one second.
b) Accuracy:
The computers are very accurate. Since the computer is
capable of doing only what it is instructed to do, faulty instructions for data
processing may lead to faulty results. This is known as Garbage In Garbage
Out(GIGO).
c): Diligence:
Computer, being a machine, does not suffer from human
traits of tiredness and lack of concentration. If four million calculations
have to be performed then the computer perform the last four million calculation
with same accuracy and speed as the first calculation.
d) Reliability:
Reliability is the measurement of the performance of a
computer, which is measured against some predetermined standard for operation
without failure. At hardware level, computer does not require any human
intervention between its processing operations. Computers have built in
diagnostic capabilities which help in the continuous monitoring of the system.
e) Storage:
Computers can store large amount of data and can recalled
the record information almost instantaneously. The main memory of the computer
is relatively small and can hold only a certain amount of data and temporary
also. So the data are stored in large on secondary storage devices such as
magnetic tape or disks permanently.
f) Versatility:
Computers are versatile in nature. It can perform
multiple tasks simultaneously with equal ease. For example, at one moment it
can be used to draft a letter, another moment it can be used to play music and
in between one can print a document as well.
g)Resource sharing:
Today computers have the capability to connect with each
other. This has made the sharing of costly resources like printers possible.
Apart from device sharing, data and information can also be shared among groups
of computers, thus creating a large information and knowledge base.
Limitations of computer:
A computer can only perform what it is programmed to do. The computer needs well defined instructions
to perform any operations. Hence Computers are unable to give any conclusion
without going through intermediate steps. A computer’s use is limited in areas
where qualitative considerations are important. For instance, It can make plans
based on situations and information, nut it cannot foresee whether they will
succeed.
Evolution
of Computers:
The need for device to do calculations
along with the growth in commerce and other human activities explains the
evolution of computers. Having the right tool to perform these tasks has always
been important for human beings. In their quest to develop efficient computing
devices, humankind developed many apparatuses. However many centuries elapsed
before technology was adequately advanced to develop computers.
Calculate with
pebbles
·
The early man was in need of counting the
cattle before and after grazing.
·
He made use the pebbles to count the cattle.
That is the genesis of calculation.
Abacus
·
In the beginning people used either their
fingers or pebbles along lines in the sand to count or add. For the sake
convenience people in Asia Minor built a counting device called abacus through
which calculations where performed using a system of sliding beads arranged on
a rack.
Napier’s Bones
In 1617 an eccentric Scotsman named John
Napier invented logarithms, that allows multiplication to be performed via
addition.
Slide Rule
Napier’s invention led directly to the slide
rule.
Pascaline
In 1642, a French mathematician, Blaise Pascal
invented the first functional automatic calculator. This brass rectangular box
is also called as Pascalaine,used eight movable dials to add numbers up to
eight figures long.
Leibniz Machine
In 1964, a German mathematician, Gottfried
Wilhem von Leibniz made a machine that could perform multiplication, division
and square root. This machine is known as the Stepped Recknoer.It was the first
mass producing calculating device which was designed to perform multiplication
by repeated additions.It worked by a system of gears and tiles. But it lacked
mechanical precision in its construction and was not reliable.
Charles Babbage
- 1792-1871
In 1822, charles babbage(Father of Computer)
Propesed a machine to perform differential equations called Difference Engine
which is powered by steam. The machine would have a stored program and could
perform calculations and print the results automatically. But it was not
completed.
Analytical
Engine 1833
In
1833, chaleds babbage developed analytical engine with input devices in the
form of perforated cards containing operating instructions and a “store” for
the memory of thousand numbers of upto fifty decimal digits long. Babbage
borrowed the idea of punch cards to encode the machine instruction from joseph
mary jacquard’s loom. Although the analytical engine never constructed the out
line basic elements of a modern computer.
In
1889, Hermon Hollorith worked for the U.S census bureau applied jacquard’s loom
concept to computing. Hollerith’s method used cards to store data which fed
into a machine that compiled the results mechanically. The start of world war 2
produce a substantial need for a computer capacity, especially for military
purposes.
Harvard
Aiken and IBM in 1944 built mark 1 using relays and electro magnetic components to replace
mechanical components. In 1946, John Eckert and John Mauchly of the Moore
School of Engineering at the University of Pennsylvania developed the
Electronic Numerical Integrator and Calculator (ENIAC).
The
computer used electronic vacuum tubes John Eckert and John Mauchly also
proposed the development of Electronic Discrete Variable Automatic Computer(EDVAC)
which was the first electronic to use the stored program concept introduced by
John van Neumann. This computer could stop any time and then resume operations.
In
1949, at Cambridge university, a team headed by Maurice Wilkes developed the
Electronic Delay Storage Automatic Calculator (EDSAC) based on John van Neumann
stored program. The machine used mercury delay lines for memory and vacuum
tubes for logic. The Eckert – Mauchly Corporation manufactured the universal
automatic computer (UNIVAC) in 1959.
In
1960’s efforts to design and develop the fastest possible computer with
greatest capacity reached a turning point with the Livermore Advanced Research
Computer (LARC) add access time of less than 1µs and the total capacity
100,000,000.
Generations of
Computers:
In computer terminology, the word generation is
described as a stage of technology development or innovation. Changing the way
the computer operate, resulting in increasingly smaller, cheaper, more
powerful, and more efficient and reliable devices are the characters of various
generations of computers. According to the type of processor installed in a
machine there are five generations of computers.
First Generation
1940 – 1956
First-generation of computers used vacuum tubes,
relied on binary-coded language or machine language, punched cards and paper tape for input and printouts for output. These Computers used vacuum tubes for
circuitry and magnetic drums for memory. In first generation computers each
machine fed with different binary codes and hence difficult to program. This
resulted in lack of versatility and speed.
Examples: ENIAC, EDVAC and UNIVAC.
Characteristic of First Generation Computers:
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Used vacuum tubes
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Large in size and non-portable
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Required much air conditioning
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Relatively slow
·
Lacked in versatility and speed
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Unreliable and prone to frequent hardware
failure
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Expensive to operate and used large amount of
electricity
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Used magnetic drum as storage media
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Used binary-coded language or machine language
(language of 0s and 1s)
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Speeds in thousands of a second
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Average storage capacity - 4000 bytes or 4K (K
stands for thousands)
Second
Generation of Computers (1956 to 1963)
Second generation of computers used transistors
which are made up of semiconductor material like germanium and silicon. Second
generation of computers relied on assembly language, punched cards for input
and printouts for output. Since transistor is a small device, the physical sizes
of computers were greatly reduced. Computers became smaller, faster, cheaper,
energy efficient and more reliable than their predecessors. In Second
generation of computers, magnetic cores were used as the primary memory and
magnetic disks as the secondary storage devices. Early high level programming
languages such as COBOL and FORTRAN also came into existence in this period.
Examples: PDP-8, IBM 1401 and IBM 7090.
Characteristic of Second Generation Computers:
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Used transistors
·
Smaller and portable
·
Required air conditioning
·
Less expensive
·
Generated less heat
·
More reliable and less prone to hardware
failure
·
Magnetic core replaced magnetic drum
·
Supported auxiliary or secondary storage
devices
·
Used assembly language (mnemonics or
abbreviations for instructions such as ADD for addition and MULT for
multiplication rather than 0s and 1s)
·
Speeds in millions of a second
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Average storage capacity 32000 or 32K
Third
Generation of Computers (1964 to Early 1970s)
Integrated circuits also called as IC consists
of a single chip with many electronic components such as transistors and
resistors fabricated on it. Third generation of computers used integrated
circuits, interfaced with operating system through keyboards and monitors
interfaced and used high level programming languages. This allowed this device
to run many different applications simultaneously with central program that
monitored the memory. Examples: NCR 395 and B6500.
Characteristics
of Third Generation of Computers:
·
Used integrated circuits
·
Smaller, cheaper, easily portable and more
reliable
·
Generated less heat and consuming less power
·
Used operating System and high level
programming languages
·
Hardware rarely failed, the maintenance cost
was quite low
·
Speeds in billions and trillions of a second
·
Average storage capacity 128000 or 128K
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Commercial production become easier and
cheaper.
Fourth
Generation of Computers (Early 1970s to Till Date)
Fourth Generation of Computers is an extension
of third Generation technology. This generation computers used the
microprocessor (circuits containing millions of transistors). Fourth Generation
of Computers led to an era of Large Scale Integration (LSI) and VLSI (Very
Large Scale Integration) technology. Large Scale Integration increased the
number of electronic components that can be fabricated on to a single chip.
VLSI (Very Large Scale Integration) and ULSI (Ultra Large Scale Integration)
technologies still increased the number of components into millions of
components that can be fabricated on to a single chip. Fourth generation of
computers used these technologies to develop personal computers. This
generation of computers could be linked to form computer networks led to the
development of internet. Graphical User Interface (GUI) operating systems are
developed. Examples: Apple II, Altair 8800 and CRAY-1.
Characteristics
of Fourth Generation of Computers:
·
Used microprocessors
·
Very small, cheap, portable and quite reliable
·
Generate negligible amount of heat
·
Very low production cost
·
Used GUI operating systems and pointing
devices (mouse)
·
Interconnection of computers led to better
communication and resource sharing
Fifth
Generation of Computers (Present and Beyond)
The process of developing Fifth Generation of
Computers is still in development stage. Fifth Generation of Computers uses
expert system concept. The expert systems is defined as a computer system that
attempts to mimic the thought process and reasoning of experts in specific
areas.
Three characteristics can be identified with
the fifth generation computers are:
·
Use
Super Large Scale Integration (SLSI) or mega chips.
·
Parallel
processing computers (previous generations are uniprocessing computers that use
only one processor for processing only one instruction at a given time) which
use more than one processor or multiple processors to process more than one
instruction at a time.
·
Based
on artificial intelligence which is a series of related technologies that try
to simulate and reproduce human behavior including thinking, speaking and
reasoning. AI comprises a group of related technologies: expert system (ES is
defined as a computer system that attempts to mimic the thought process and
reasoning of expert in specific area), natural language processing (NLP),
speech recognition, vision recognition and robotics.
Classification
of Computers:
Computers are classified based on physical
size, performance, data-processing ability and application areas. Generally computers
can be classified into four major categories such as micro, mini, mainframe and
supercomputers.
Microcomputers:
A microcomputer is a small, low-cost digital
computer which consists of a microprocessor, storage unit, input channel,
output channel. The micro computers are generally smallest of the computer
family and designed for individual users only. Microcomputers include desktop,
laptop and hand-held devices such as Personal Digital Assistants (PDAs).
Desktop
Computer:
Desktop computer also known as Personal
Computer (PC) is intended for stand-alone use by an individual. Some of the
major PC manufacturers are APPLE, IBM, DELL and Hewlett-Packard.
Laptop:
A laptop known as notebook computer is a
portable computer. Laptops are powered by rechargeable batteries. However, they
are expensive as compared to desktop computers.
Difference
between Desktop and Laptop:
Desktop
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Laptop
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Also
called as personal computer
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Also
called as notebook
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Large
in size
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Smaller
when compared to desktop
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Non-portable
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Portable
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Powered
by direct electrical line
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Powered
by rechargeable batteries
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Components
are not integrated as a single unit
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All
parts are integrated as a single unit
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Individuals
RAM units are used by processor and VDU
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RAM
is being shared among VDU and processor
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Hand-held
Computers:
A
hand-held computer also called as palmtop computer such as Portable Digital
Assistance (PDA) is a portable computer that can be conveniently be stored in a
pocket and used while the user is holding it. PDA uses a pen or electronic
stylus instead of keyboard for input, small cards to store programs and data
instead of disk drive and can be connected to a printer or disk drive to
generate output and store data.
Example:
Apple Newton, Casio Cassiopeia and Franklin eBookMan.
Minicomputers:
A minicomputer called as mid-range computer is
designed to meet the computing needs of several people simultaneously in a
small to medium sized business environment. It is about the size of a
two-drawer filing cabinet. It is capable of supporting from four to two hundred
simultaneous users. Minicomputers are usually multi-user systems. They are also
used for real-time controls and engineering design work. Example: PDP 11, IBM(8000 series) and VAX
7500.
Mainframes:
Mainframe is an ultra-high performance
computer made for high-volume, processor-intensive computing. Mainframes are
powerful computers used mainly by large organizations for critical
applications, typically bulk data processing such as census, industry and
consumer statistics, enterprise resource planning, and financial transaction
processing and having extensive data storage. Mainframes are second largest (in
compatibility and size) of the computer family, the largest being the
supercomputers.
Example:
IBM’s ES000, VAX 8000 and CDC 6600.
Supercomputers:
Supercomputers are special purpose machines
with highest processing power at a given time for solving scientific and
engineering problems. Supercomputers are especially designed to maximize the
number of floating point operation per second(FLOPS).Supercomputer contains
number of CPUs that operate in parallel to process millions of Floating Point
Operations per Second (FLOPS).
Example:
CRAY-3, Cyber 205 and PARAM
In
2003, India’s Center for Development of Advanced Computing (C-DAC) developed
supercomputer namely PARAM Padma with processing speed up to 1 Teraflop per
second.