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 A programmable machine. The
two principal characteristics of a computer are:
Modern computers are
electronic and digital. The actual machinery -- wires,
transistors, and circuits -- is called hardware; the
instructions and data are called software.
More About Computer are written Below:
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History Of Computer Technology
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Kind Of Computers
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Computer Components (Hardware)
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Usage Of Computer in Our Daily Life
History of Computer
Technology
A
complete history of
computing would include a multitude of diverse devices such as
the ancient Chinese abacus, the Jacquard loom (1805) and
Charles Babbage's ``analytical engine'' (1834). It would also
include discussion of mechanical, analog and digital computing
architectures. As late as the 1960s, mechanical devices, such
as the Merchant calculator, still found widespread application
in science and engineering. During the early days of
electronic computing devices, there was much discussion about
the relative merits of analog vs. digital computers. In fact,
as late as the 1960s, analog computers were routinely used to
solve systems of finite difference equations arising in oil
reservoir modeling. In the end, digital computing devices
proved to have the power, economics and scalability necessary
to deal with large scale computations. Digital computers now
dominate the computing world in all areas ranging from the
hand calculator to the supercomputer and are pervasive
throughout society. Therefore, this brief sketch of the
development of scientific computing is limited to the area of
digital, electronic computers.
The evolution of digital computing is often divided into
generations. Each generation is characterized by dramatic
improvements over the previous generation in the technology
used to build computers, the internal organization of computer
systems, and programming languages. Although not usually
associated with computer generations, there has been a steady
improvement in algorithms, including algorithms used in
computational science. The following history has been
organized using these widely recognized generations as
mileposts.
The
Mechanical Era (1623-1945)
The idea
of using machines to solve mathematical problems can be traced
at least as far as the early 17th century. Mathematicians who
designed and implemented calculators that were capable of
addition, subtraction, multiplication, and division included
Wilhelm Schick hard, Blaise Pascal, and Gottfried Leibnitz.
The first multi-purpose,
i.e. programmable, computing device was probably Charles
Babbage's Difference Engine, which was begun in 1823 but never
completed. A more ambitious machine was the Analytical Engine.
It was designed in 1842, but unfortunately it also was only
partially completed by Babbage. Babbage was truly a man ahead
of his time: many historians think the major reason he was
unable to complete these projects was the fact that the
technology of the day was not reliable enough. In spite of
never building a complete working machine, Babbage and his
colleagues, most notably Ada, Countess of Lovelace, recognized
several important programming techniques, including
conditional branches, iterative loops and index variables.
A machine inspired by Babbage's design was arguably the first
to be used in computational science. George Scheutz read of
the difference engine in 1833, and along with his son Edvard
Scheutz began work on a smaller version. By 1853 they had
constructed a machine that could process 15-digit numbers and
calculate fourth-order differences. Their machine won a gold
medal at the Exhibition of Paris in 1855, and later they sold
it to the Dudley Observatory in Albany, New York, which used
it to calculate the orbit of Mars. One of the first commercial
uses of mechanical computers was by the US Census Bureau,
which used punch-card equipment designed by Herman Hollerith
to tabulate data for the 1890 census. In 1911 Hollerith's
company merged with a competitor to found the corporation
which in 1924 became International Business Machines.
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First Generation Electronic Computers (1937-1953)
Three machines have been
promoted at various times as the first electronic computers.
These machines used electronic switches, in the form of vacuum
tubes, instead of electromechanical relays. In principle the
electronic switches would be more reliable, since they would
have no moving parts that would wear out, but the technology
was still new at that time and the tubes were comparable to
relays in reliability. Electronic components had one major
benefit, however: they could ``open'' and ``close'' about
1,000 times faster than mechanical switches.
The earliest attempt to build an electronic computer was by J.
V. Atanasoff, a professor of physics and mathematics at Iowa
State, in 1937. Atanasoff set out to build a machine that
would help his graduate students solve systems of partial
differential equations. By 1941 he and graduate student
Clifford Berry had succeeded in building a machine that could
solve 29 simultaneous equations with 29 unknowns. However, the
machine was not programmable, and was more of an electronic
calculator.
A second early electronic
machine was Colossus, designed by Alan Turing for the British
military in 1943. This machine played an important role in
breaking codes used by the German army in World War II.
Turing's main contribution to the field of computer science
was the idea of the Turing machine, a mathematical formalism
widely used in the study of computable functions. The
existence of Colossus was kept secret until long after the war
ended, and the credit due to Turing and his colleagues for
designing one of the first working electronic computers was
slow in coming.
The first general purpose
programmable electronic computer was the Electronic Numerical
Integrator and Computer (ENIAC), built by J. Presper Eckert
and John V. Mauchly at the University of Pennsylvania. Work
began in 1943, funded by the Army Ordnance Department, which
needed a way to compute ballistics during World War II. The
machine wasn't completed until 1945, but then it was used
extensively for calculations during the design of the hydrogen
bomb. By the time it was decommissioned in 1955 it had been
used for research on the design of wind tunnels, random number
generators, and weather prediction. Eckert, Mauchly, and John
von Neumann, a consultant to the ENIAC project, began work on
a new machine before ENIAC was finished. The main contribution
of EDVAC, their new project, was the notion of a stored
program. There is some controversy over who deserves the
credit for this idea, but none over how important the idea was
to the future of general purpose computers. ENIAC was
controlled by a set of external switches and dials; to change
the program required physically altering the settings on these
controls. These controls also limited the speed of the
internal electronic operations. Through the use of a memory
that was large enough to hold both instructions and data, and
using the program stored in memory to control the order of
arithmetic operations, EDVAC was able to run orders of
magnitude faster than ENIAC. By storing instructions in the
same medium as data, designers could concentrate on improving
the internal structure of the machine without worrying about
matching it to the speed of an external control.
Regardless of who deserves
the credit for the stored program idea, the EDVAC project is
significant as an example of the power of interdisciplinary
projects that characterize modern computational science. By
recognizing that functions, in the form of a sequence of
instructions for a computer, can be encoded as numbers, the
EDVAC group knew the instructions could be stored in the
computer's memory along with numerical data. The notion of
using numbers to represent functions was a key step used by
Goedel in his incompleteness theorem in 1937, work which von
Neumann, as a logician, was quite familiar with. Von Neumann's
background in logic, combined with Eckert and Mauchly's
electrical engineering skills, formed a very powerful
interdisciplinary team.
Software technology during this period was very primitive. The
first programs were written out in machine code, i.e.
programmers directly wrote down the numbers that corresponded
to the instructions they wanted to store in memory. By the
1950s programmers were using a symbolic notation, known as
assembly language, then hand-translating the symbolic notation
into machine code. Later programs known as assemblers
performed the translation task.
As primitive as they were, these first electronic machines
were quite useful in applied science and engineering.
Atanasoff estimated that it would take eight hours to solve a
set of equations with eight unknowns using a Marchant
calculator, and 381 hours to solve 29 equations for 29
unknowns. The Atanasoff-Berry computer was able to complete
the task in under an hour. The first problem run on the ENIAC,
a numerical simulation used in the design of the hydrogen
bomb, required 20 seconds, as opposed to forty hours using
mechanical calculators. Eckert and Mauchly later developed
what was arguably the first commercially successful computer,
the UNIVAC; in 1952, 45 minutes after the polls closed and
with 7% of the vote counted, UNIVAC predicted Eisenhower would
defeat Stevenson with 438 electoral votes (he ended up with
442).
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Second Generation
(1954-1962)
The second generation saw
several important developments at all levels of computer
system design, from the technology used to build the basic
circuits to the programming languages used to write scientific
applications.
Electronic switches in this
era were based on discrete diode and transistor technology
with a switching time of approximately 0.3 microseconds. The
first machines to be built with this technology include TRADIC
at Bell Laboratories in 1954 and TX-0 at MIT's Lincoln
Laboratory. Memory technology was based on magnetic cores
which could be accessed in random order, as opposed to mercury
delay lines, in which data was stored as an acoustic wave that
passed sequentially through the medium and could be accessed
only when the data moved by the I/O interface.
Important innovations in computer architecture included index
registers for controlling loops and floating point units for
calculations based on real numbers. Prior to this accessing
successive elements in an array was quite tedious and often
involved writing self-modifying code (programs which modified
themselves as they ran; at the time viewed as a powerful
application of the principle that programs and data were
fundamentally the same, this practice is now frowned upon as
extremely hard to debug and is impossible in most high level
languages). Floating point operations were performed by
libraries of software routines in early computers, but were
done in hardware in second generation machines.
During this second generation many high level programming
languages were introduced, including FORTRAN (1956), ALGOL
(1958), and COBOL (1959). Important commercial machines of
this era include the IBM 704 and its successors, the 709 and
7094. The latter introduced I/O processors for better
throughput between I/O devices and main memory.
The second generation also saw the first two supercomputers
designed specifically for numeric processing in scientific
applications. The term ``supercomputer'' is generally reserved
for a machine that is an order of magnitude more powerful than
other machines of its era. Two machines of the 1950s deserve
this title. The Livermore Atomic Research Computer (LARC) and
the IBM 7030 (aka Stretch) were early examples of machines
that overlapped memory operations with processor operations
and had primitive forms of parallel processing.
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Third Generation
(1963-1972)
The third generation
brought huge gains in computational power. Innovations in this
era include the use of integrated circuits, or ICs
(semiconductor devices with several transistors built into one
physical component), semiconductor memories starting to be
used instead of magnetic cores, microprogramming as a
technique for efficiently designing complex processors, the
coming of age of pipelining and other forms of parallel
processing (described in detail in Chapter CA), and the
introduction of operating systems and time-sharing.
The first ICs were based on
small-scale integration (SSI) circuits, which had around 10
devices per circuit (or ``chip''), and evolved to the use of
medium-scale integrated (MSI) circuits, which had up to 100
devices per chip. Multilayered printed circuits were developed
and core memory was replaced by faster, solid state memories.
Computer designers began to take advantage of parallelism by
using multiple functional units, overlapping CPU and I/O
operations, and pipelining (internal parallelism) in both the
instruction stream and the data stream. In 1964, Seymour Cray
developed the CDC 6600, which was the first architecture to
use functional parallelism. By using 10 separate functional
units that could operate simultaneously and 32 independent
memory banks, the CDC 6600 was able to attain a computation
rate of 1 million floating point operations per second (1
Mflops). Five years later CDC released the 7600, also
developed by Seymour Cray. The CDC 7600, with its pipelined
functional units, is considered to be the first vector
processor and was capable of executing at 10 Mflops. The IBM
360/91, released during the same period, was roughly twice as
fast as the CDC 660. It employed instruction look ahead,
separate floating point and integer functional units and
pipelined instruction stream. The IBM 360-195 was comparable
to the CDC 7600, deriving much of its performance from a very
fast cache memory. The SOLOMON computer, developed by
Westinghouse Corporation, and the ILLIAC IV, jointly developed
by Burroughs, the Department of Defense and the University of
Illinois, were representative of the first parallel computers.
The Texas Instrument Advanced Scientific Computer (TI-ASC) and
the STAR-100 of CDC were pipelined vector processors that
demonstrated the viability of that design and set the
standards for subsequent vector processors.
Early in the this third
generation Cambridge and the University of London cooperated
in the development of CPL (Combined Programming Language,
1963). CPL was, according to its authors, an attempt to
capture only the important features of the complicated and
sophisticated ALGOL. However, like ALGOL, CPL was large with
many features that were hard to learn. In an attempt at
further simplification, Martin Richards of Cambridge developed
a subset of CPL called BCPL (Basic Computer Programming
Language, 1967). In 1970 Ken Thompson of Bell Labs developed
yet another simplification of CPL called simply B, in
connection with an early implementation of the UNIX operating
system. comment):
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Fourth Generation
(1972-1984)
The next generation of
computer systems saw the use of large scale integration (LSI -
1000 devices per chip) and very large scale integration (VLSI
- 100,000 devices per chip) in the construction of computing
elements. At this scale entire processors will fit onto a
single chip, and for simple systems the entire computer
(processor, main memory, and I/O controllers) can fit on one
chip. Gate delays dropped to about 1ns per gate.
Semiconductor memories
replaced core memories as the main memory in most systems;
until this time the use of semiconductor memory in most
systems was limited to registers and cache. During this
period, high speed vector processors, such as the CRAY 1, CRAY
X-MP and CYBER 205 dominated the high performance computing
scene. Computers with large main memory, such as the CRAY 2,
began to emerge. A variety of parallel architectures began to
appear; however, during this period the parallel computing
efforts were of a mostly experimental nature and most
computational science was carried out on vector processors.
Microcomputers and workstations were introduced and saw wide
use as alternatives to time-shared mainframe computers.
Developments in software
include very high level languages such as FP (functional
programming) and Prolog (programming in logic). These
languages tend to use a declarative programming style as
opposed to the imperative style of Pascal, C, FORTRAN, et al.
In a declarative style, a programmer gives a mathematical
specification of what should be computed, leaving many details
of how it should be computed to the compiler and/or runtime
system. These languages are not yet in wide use, but are very
promising as notations for programs that will run on massively
parallel computers (systems with over 1,000 processors).
Compilers for established languages started to use
sophisticated optimization techniques to improve code, and
compilers for vector processors were able to victories simple
loops (turn loops into single instructions that would initiate
an operation over an entire vector).
Two important events marked
the early part of the third generation: the development of the
C programming language and the UNIX operating system, both at
Bell Labs. In 1972, Dennis Ritchie, seeking to meet the design
goals of CPL and generalize Thompson's B, developed the C
language. Thompson and Ritchie then used C to write a version
of UNIX for the DEC PDP-11. This C-based UNIX was soon ported
to many different computers, relieving users from having to
learn a new operating system each time they change computer
hardware. UNIX or a derivative of UNIX is now a de facto
standard on virtually every computer system.
An important event in the
development of computational science was the publication of
the Lax report. In 1982, the US Department of Defense (DOD)
and National Science Foundation (NSF) sponsored a panel on
Large Scale Computing in Science and Engineering, chaired by
Peter D. Lax. The Lax Report stated that aggressive and
focused foreign initiatives in high performance computing,
especially in Japan, were in sharp contrast to the absence of
coordinated national attention in the United States. The
report noted that university researchers had inadequate access
to high performance computers. One of the first and most
visible of the responses to the Lax report was the
establishment of the NSF supercomputing centers. Phase I on
this NSF program was designed to encourage the use of high
performance computing at American universities by making
cycles and training on three (and later six) existing
supercomputers immediately available. Following this Phase I
stage, in 1984-1985 NSF provided funding for the establishment
of five Phase II supercomputing centers.
The Phase II centers,
located in San Diego (San Diego Supercomputing Center);
Illinois (National Center for Supercomputing Applications);
Pittsburgh (Pittsburgh Supercomputing Center); Cornell
(Cornell Theory Center); and Princeton (John von Neumann
Center), have been extremely successful at providing computing
time on supercomputers to the academic community. In addition
they have provided many valuable training programs and have
developed several software packages that are available free of
charge. These Phase II centers continue to augment the
substantial high performance computing efforts at the National
Laboratories, especially the Department of Energy (DOE) and
NASA sites.
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Fifth
Generation (1984-1990)
The development of the next
generation of computer systems is characterized mainly by the
acceptance of parallel processing. Until this time parallelism
was limited to pipelining and vector processing, or at most to
a few processors sharing jobs. The fifth generation saw the
introduction of machines with hundreds of processors that
could all be working on different parts of a single program.
The scale of integration in semiconductors continued at an
incredible pace - by 1990 it was possible to build chips with
a million components - and semiconductor memories became
standard on all computers.
Other new developments were
the widespread use of computer networks and the increasing use
of single-user workstations. Prior to 1985 large scale
parallel processing was viewed as a research goal, but two
systems introduced around this time are typical of the first
commercial products to be based on parallel processing. The
Sequent Balance 8000 connected up to 20 processors to a single
shared memory module (but each processor had its own local
cache). The machine was designed to compete with the DEC
VAX-780 as a general purpose Unix system, with each processor
working on a different user's job. However Sequent provided a
library of subroutines that would allow programmers to write
programs that would use more than one processor, and the
machine was widely used to explore parallel algorithms and
programming techniques.
The Intel iPSC-1, nicknamed
``the hypercube'', took a different approach. Instead of using
one memory module, Intel connected each processor to its own
memory and used a network interface to connect processors.
This distributed memory architecture meant memory was no
longer a bottleneck and large systems (using more processors)
could be built. The largest iPSC-1 had 128 processors. Toward
the end of this period a third type of parallel processor was
introduced to the market. In this style of machine, known as a
data-parallel or SIMD, there are several thousand very simple
processors. All processors work under the direction of a
single control unit; i.e. if the control unit says ``add a to
b'' then all processors find their local copy of a and add it
to their local copy of b. Machines in this class include the
Connection Machine from Thinking Machines, Inc., and the MP-1
from MasPar, Inc.
Scientific computing in
this period was still dominated by vector processing. Most
manufacturers of vector processors introduced parallel models,
but there were very few (two to eight) processors in this
parallel machines. In the area of computer networking, both
wide area network (WAN) and local area network (LAN)
technology developed at a rapid pace, stimulating a transition
from the traditional mainframe computing environment toward a
distributed computing environment in which each user has their
own workstation for relatively simple tasks (editing and
compiling programs, reading mail) but sharing large, expensive
resources such as file servers and supercomputers. RISC
technology (a style of internal organization of the CPU) and
plummeting costs for RAM brought tremendous gains in
computational power of relatively low cost workstations and
servers. This period also saw a marked increase in both the
quality and quantity of scientific visualization.
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Sixth Generation (1990 -
)
Transitions between
generations in computer technology are hard to define,
especially as they are taking place. Some changes, such as the
switch from vacuum tubes to transistors, are immediately
apparent as fundamental changes, but others are clear only in
retrospect. Many of the developments in computer systems since
1990 reflect gradual improvements over established systems,
and thus it is hard to claim they represent a transition to a
new ``generation'', but other developments will prove to be
significant changes.
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Kinds Of Computers
(According To Size &
Power)
Computers can be generally
classified by size and power as follows,
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Personal Computer
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Workstation
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Minicomputer
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Mainframe
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Supercomputer
Personal Computer
A small, single-user
computer based on a microprocessor. In addition to the
microprocessor, a personal computer has a keyboard for
entering data, a monitor for displaying information, and a
storage device for saving data.
A small,
relatively inexpensive computer designed for an individual
user. In price, personal computers range anywhere from a few
hundred dollars to thousands of dollars. All are based on the
microprocessor technology that enables manufacturers to put an
entire CPU on one chip. Businesses use personal computers for
word processing, accounting, desktop publishing, and for
running spreadsheet and database management applications. At
home, the most popular use for personal computers is for
playing games.
Personal computers first appeared in the late 1970s. One of
the first and most popular personal computers was the Apple
II, introduced in 1977 by Apple Computer. During the late
1970s and early 1980s, new models and competing operating
systems seemed to appear daily. Then, in 1981, IBM entered the
fray with its first personal computer, known as the IBM PC.
The IBM PC quickly became the personal computer of choice, and
most other personal computer manufacturers fell by the
wayside. One of the few companies to survive IBM's onslaught
was Apple Computer, which remains a major player in the
personal computer marketplace.
Other companies adjusted to IBM's dominance by building IBM
clones, computers that were internally almost the same as the
IBM PC, but that cost less. Because IBM clones used the same
microprocessors as IBM PCs, they were capable of running the
same software. Over the years, IBM has lost much of its
influence in directing the evolution of PCs. Many of its
innovations, such as the MCA expansion bus and the OS/2
operating system, have not been accepted by the industry or
the marketplace.
Today, the world of personal computers is basically divided
between Apple Macintoshes and PCs. The principal
characteristics of personal computers are that they are
single-user systems and are based on microprocessors. However,
although personal computers are designed as single-user
systems, it is common to link them together to form a network.
In terms of power, there is great variety. At the high end,
the distinction between personal computers and workstations
has faded. High-end models of the Macintosh and PC offer the
same computing power and graphics capability as low-end
workstations by Sun Microsystems, Hewlett-Packard, and DEC.
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Workstation
A powerful, single-user computer. A workstation is like a
personal computer, but it has a more powerful microprocessor
and a higher-quality monitor.
1. A
type of computer used for engineering applications (CAD/CAM),
desktop publishing, software development, and other types of
applications that require a moderate amount of computing power
and relatively high quality graphics capabilities.
Workstations generally come with a large, high-resolution
graphics screen, at least 64 MB (megabytes) of RAM, built-in
network support, and a graphical user interface. Most
workstations also have a mass storage device such as a disk
drive, but a special type of workstation, called a diskless
workstation, comes without a disk drive. The most common
operating systems for workstations are UNIX and Windows NT.
In terms of computing power, workstations lie between personal
computers and minicomputers, although the line is fuzzy on
both ends. High-end personal computers are equivalent to
low-end workstations. And high-end workstations are equivalent
to minicomputers.
Like personal computers, most workstations are single-user
computers. However, workstations are typically linked together
to form a local-area network, although they can also be used
as stand-alone systems.
2. In networking, workstation refers to any computer
connected to a local-area network. It could be a workstation
or a personal computer.
Workstation also is spelled work station or work-station.
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Minicomputer
A
multi-user computer capable of supporting from 10 to hundreds
of users simultaneously. 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.
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Mainframe
A powerful multi-user computer capable of supporting many
hundreds or thousands of users simultaneously. 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. The
distinction between small mainframes and minicomputers is
vague, depending really on how the manufacturer wants to
market its machines.
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Supercomputer
An extremely fast computer that can perform hundreds of
millions of instructions per second. The fastest 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
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Computer Components
CPU
Motherboard
Hard Drive
Video Card
Memory
Cases
CD-ROM/DVD-ROM
SCSI Card
Monitor
Printer
Modem
Audio
Digital Cameras
Digital Camcorders
Cooling
Input Devices
CPU
(Central
Processing Unit)
So
what's a CPU? It stands for Central Processing Unit. Many
users erroneously refer to the whole computer box as the CPU.
In fact, the CPU itself is only about 1.5 inches square. The
CPU does exactly what it stands for. It is the control unit
that processes all* of the instructions for the computer.
Consider it to be the "brain" of the computer. It does all
the thinking. So, would you like to have a fast or slow
brain? Obviously, the answer to this question makes the CPU
the most important part of the computer. The speed here is
the most significant. The processor's (CPU's) speed is given
in a MHz or GHz rating 3 GHz is roughly 3,000 MHz. In today's
computers, the video cards, sound cards, etc. also process
instructions, but the majority of the burden lays on the CPU.
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Motherboard
The
best way to describe the motherboard goes along well with my
human body analogy that I used for the CPU. The CPU is the
brain, and the motherboard is the nervous system. Therefore,
just as a person would want to have fast communication to the
body parts, you want fast communication between the parts of
your computer. Fast communication isn't as important as
reliable communication though. If your brain wanted to move
your arm, you want to be sure the nervous system can
accurately and consistently carry the signals to do that!
Thus, in my opinion, the motherboard is the second most
important part of the computer.
The motherboard is the circuit board to which all the other
components of the computer connect in some way. The video
card, sound card, IDE hard drive, etc. all plug into the
motherboard's various slots and connectors. The CPU also
plugs into the motherboard via a Socket or a Slot.
Hard
Disk
As the primary
communication device to the rest of the computer, the hard
drive is very important. The hard drive stores most of a
computer's information including the operating system and all
of your programs. Having a fast CPU is not of much use if you
have a slow hard drive. The reason for this is because the
CPU will just spend time waiting for information from the hard
drive. During this time, the CPU is just twiddling it's
thumbs...
The hard drive stores all the data on your computer - your
text documents, pictures, programs, etc. If something goes
wrong with your hard drive, it is possible that all your data
could be lost forever. Today's hard drives have become much
more reliable, but hard drives are still one of the components
most likely to fail because they are one of the few components
with moving parts. The hard drive has round discs that store
information as 1s and 0s very densely packed around the disc.
Video cards
Video cards provide the
means for the computer to "talk" to your monitor so it can
display what the computer is doing. Older video cards were
"2D," or "3D," but today's are all "2D/3D" combos. The 3D is
mostly useful for gaming, but in some applications can be
useful in 3D modeling, etc. Video cards have their own
advanced processing chips that make all kinds of calculations
to make scenes look more realistic. The many video cards out
there are based on much smaller number of different chipsets
(that are run at different speeds or have slight differences
in the chipsets). Different companies buy these chipsets and
make their own versions of the cards based on the chipsets.
For the most part, video cards based on the same chipset with
the same amount of RAM are about equivalent in performance.
However, some brands will use faster memory or other small
optimizations to improve the speed. The addition of other
extras like "dual head" (support for two monitors) or better
cooling fans may also appear by different brands. At any
rate, the first decision to make is what chipset you want your
video card to use. If you aren't interested in games, then
the choice of chipset isn't too difficult - just about any
will do for the 2D desktop applications. There's no point in
buying a video card over $100 if you don't plan to play games.
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Memory
All programs, instructions,
and data must be stored in system memory before the computer
can use it. It will hold recently used programs,
instructions, and data in memory if there is room. This
provides quick access (much faster than hard drives) to
information. The more memory you have, the more information
you will have fast access to and the better your computer will
perform. Memory is much like the short term memory in your
brain. It holds your most recent information for quick access.
Just as you want to accurately remember this information in
your head, you want your computer's memory to have the correct
information as well, or problems will obviously occur. Bad
memory is one of the more common causes of computer crashes,
and also the most difficult problem to diagnose. Because of
this, making sure you get good RAM the first time around is
very important.
There are many, many different types of memory for different
tasks. The main ones today are DDR PCxx00 SDRAM DIMMs (this
includes PC2700, PC3200, etc.) and Direct RDRAM RIMMs.
Computer's Case
The computer's case serves
several functions. The motherboard is bolted down to the case
so that the case protects it and all other components. The
metal in the case also serves to ground the motherboard. The
case's power supply converts power into a form the motherboard
can use.
A good case should have
ample expansion bays to be able to add additional internal and
external devices. It should have a strong enough power supply
to power all the components you plan to add to your computer.
The case should be designed aerodynamically so that airflow
will flow in through the front and out through the back to
properly dissipate all hot air. The case also needs to be
sturdy enough to prevent components from moving around.
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CD/DVD-ROM Drive
CD-ROM drives are necessary
today for most programs. A single CD can store up to 650 MB of
data (newer CD-Rs allow for 700 MB of data, perhaps more with
"overburn"). Fast CD-ROM drives have been a big topic in the
past, but all of today's CD-ROM drives are sufficiently fast.
Of course, it's nice to have the little bits of extra speed.
However, when you consider CD-ROM drives are generally used
just to install a program or copy CDs, both of which are
usually done rarely on most users' computers, the extra speed
isn't usually very important. The speed can play a big role
if you do a lot of CD burning at high speeds or some audio
extraction from audio CDs (i.e. converting CDs to MP3s).
CD-R/RW (which stands for
Recordable / Rewritable) drives (aka burners, writers) allow a
user to create their own CDs of audio and/or data. These
drives are great for backup purposes (backup your computer's
hard drive or backup your purchased CDs) and for creating your
own audio CD compilations (not to mention other things like
home movies, multimedia presentations, etc.).
DVD-ROM drives can store up
to 4 GB of data or about 6 times the size of a regular CD (not
sure on the exact size, but suffice to say it's a very large
storage medium). DVDs look about the same and are the same
size as a CD-ROM. DVD drives can also read CD-ROM drives, so
you don't usually need a separate CD-ROM drive. DVD drives
have become low enough in price that there isn't much point in
purchasing a CD-ROM drive instead of a DVD-ROM drive. Some
companies even make CD burner drives that will also read DVDs
(all in one). DVD's most practical use is movies. The DVD
format allows for much higher resolution digital recording
that looks much clearer than VCR recordings.
DVD recordable drives are
available in a couple of different formats - DVD-R or DVD+R
with a RW version of each. These are slightly different discs
and drives (although some drives support writing to both
formats). One is not much better than the other, so it really
boils down to price of the media (and also availability of the
media).
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SCSI card
A SCSI card is a card that
will control the interface between SCSI versions of hard
drives, CD-ROM drives, CD-ROM burners, removable drives,
external devices such as scanners, and any other SCSI
components. Most fit in a PCI slot and there is a wide range
of types. The three main types of connectors on these cards
are 25-pin for SCSI-1, 50-pin for Narrow SCSI, and 68-pin for
Wide SCSI (and Ultra-Wide SCSI, Ultra2-SCSI, Ultra160 SCSI,
and Ultra 320 SCSI - all of which use a 68 pin connector).
SCSI controllers provide
fast access to very fast SCSI hard drives. They can be much
faster than the IDE controllers that are already integrated
your computer's motherboard. SCSI controllers have their own
advanced processing chips, which allows them to rely less on
the CPU for handling instructions than IDE controllers do.
For the common user, SCSI
controllers are overkill, but for high end servers and/or the
performance freaks of the world, SCSI is the way to go. SCSI
controllers are also much more expensive than the free IDE
controller already included on your motherboard. There is also
a large premium in price for the SCSI hard drives themselves.
Unless you have deep pockets, there isn't much of a point in
going with a SCSI controller.
Many people buy SCSI
controllers just for use with their CD-ROM burners and CD-ROM
drives (these drives must be SCSI drives of course).
SCSI cards also have the
ability to have up 15 devices or more per card, while a single
IDE controller is limited to only 4 devices (some motherboards
now come with more than one IDE controller though). SCSI cards
allow these drives to be in a chain along the cable. Each
drive on the cable has to have a separate SCSI ID (this can be
set by jumpers on the drive). The last drive on the end of the
cable (or the cable itself) has to "terminate" the chain (you
turn termination on by setting a termination jumper on the
drive - or use a cable that has a terminator at the end of
it).
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Monitors
Monitors obviously display
what is going on in your computer. They can run at various
resolutions and refresh rates. 640x480 is the default
resolution for the Windows operating systems (this is a low
resolution where objects appear large and blocky). 640x480
just means that 640 pixels are fit across the top of your
monitor and 480 up and down. Most users prefer higher
resolutions such as 800x600 or 1024x768 all the way up to
1600x1200 (and higher for graphics professionals). The higher
resolutions make objects smaller, but clearer (because more
pixels are fit in the screen). You can fit more objects on a
screen when it is in a higher resolution. Larger monitors are
better for running at the higher resolutions. If you run a
high resolution on a small monitor, the text may be hard to
read because of its small size, despite the clarity.
The refresh rate is how
fast the monitor can refresh (redraw) the images on the
screen. The faster it can do this, the smoother your picture
will be and the less "flicker" you will see.
The monitor has a lot to do
with the quality of the picture produced by your video card,
but it doesn't actuall "produce" the graphics - the video card
does all this processing. But, if your video card is producing
a bright detailed picture and your monitor is dim and blurry,
the picture will come out the same way.
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Printer
As you know, a printer
outputs data from your computer on a piece of paper. There
are many different types of printers (most common are laser
and inkjet), and many printers are better than others for
different tasks (printing photographs, clear text, etc.).
Laser printers aren't necessarily better quality than inkjets
anymore, although they once were. If you want to be able to
print in color, inkjet printers are the best option for the
cost conscious too. Some of today's "office inkjet" printers
also have other functions including scanning, faxing, copying,
etc. While the scan and copy quality usually aren't that
great, the quality is generally good enough for most office /
home office situations.
Modem
If you are at home, then
you are most likely using a modem to view this page right now
(dial-up modem, cable modem, or DSL modem). The modem is what
hosts the communication between your computer and the
computers you are connecting to over the Internet. If you're
on a network, then you're using a network card (Ethernet card
most likely - and that may connect to your cable or DSL
modem). A modem uses your phone line to transfer data to and
from the other computers. Newer cable modems and DSL modems
provide about 10 times the speed of a regular phone modem.
These are usually external and plug into a network card in
your computer.
Modem stands for "modulator
/ demodulator" and it encodes and decodes signals sent to and
from the network servers. Good modems should be able to do
all the encoding / decoding work on their own without having
to rely on your computer's CPU to do the work.
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Audio
Most computers require a
sound card to decode sound files into audio that can be sent
to your speakers (some have it build into the motherboard).
Newer sound cards connect to PCI slots, but some of the older
ones connect to ISA slots on your motherboard. Good sound
cards allow you to play games and hear "3D audio" that makes
it sounds like certain events are actually happening behind
you. Some sound cards even do Dolby 5.1 decoding to allow you
to listen to DVDs with full surround sound.
Computer speakers are
different from regular stereo speakers in that they need to be
shielded. They are often more expensive, and there are fewer
high quality computer speakers than home stereo speakers.
Speakers come in a variety of formats including quad speaker
setups / 4.1 (2 front satellite speakers, 2 rear satellite
speakers, and a subwoofer), 2 speakers setups, 2.1 speaker
setups (2 satellite speakers and a subwoofer), and 5.1 speaker
sets (2 front satellite speakers, 1 front center channel
speaker, 2 rear satellite speakers, and a subwoofer).
Digital cameras
Digital cameras record images
onto flash memory instead of onto film. They're great because
you can see the result right away on the camera's screen.
They also allow you to crop images however you'd like, print
them at home on your computer right away, and selectively
print pictures rather than wasting money on film and
development costs of pictures you don't really want. If you
prefer, you can also send your digital pictures off for
processing and printing.
One other item to note - with regular 35 mm cameras you can
easily get them in a digital format. Many film development
companies offer an Internet upload option (at Wal-Mart for
example, this is just 97 cents for the entire roll in addition
to your development costs).
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Digital camcorders
Digital camcorders still store
video onto a tape, but they store it digitally and at a higher
resolution that analog camcorders. With digital camcorders
that have FireWire out (and FireWire in on your computer), you
don't need a video capture card to get video onto your PC,
edit it, and create DVDs.
CPU cooling fans
I'm going to focus on CPU
cooling fans here, but also discuss case fans a little.
Obviously, these keep your CPU and case cool! If they get too
hot, your system can crash and your CPU could eventually fail.
Input devices
Mouse,
Keyboard, Floppy Drive, Scanner, Joy stick, CD Rom, Flash
Drive etc.
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Usage Of
Computer In Our Daily Life
There is a big influence of
technique on our daily life. Electronic devices, multimedia
and computers are things we have to deal with everyday.
Especially the Internet is becoming more and more important
for nearly everybody as it is one of the newest and most
forward-looking media and surely “the” medium of the future.
Therefore we thought that it would be necessary to think about
some good and bad aspects of how this medium influence |
