UNIT
I
1.1 INTRODUCTION
A computer is a machine capable of
automatically processing data according to instruction lists given. Data
processing includes, but not limited to, carrying out arithmetic operations,
comparing logical values, as well as, transmitting, receiving and storing
information. Data processing tasks, no matter how long or complex they are, can
be performed with series of some simple commands, considered “native” to
the computers processing those data. A
personal computer (PC) is comprised of hardware, an operating system and
software. Each of those components is fairly complex; however this article
provides a basic description of their function and how they work together.
The Hardware
The
hardware are the parts of computer itself including the Central
Processing Unit (CPU) and related microchips and micro-circuitry, keyboards,
monitors, case
and drives
(hard, CD, DVD, floppy, optical, tape, etc...). Other extra parts called
peripheral components or devices include mouse, printers,
modems, scanners,
digital cameras
and cards (sound,
colour, video)
etc... Together they are often referred to as a personal computer.
The Operating System
An operating system (OS) is a system
software that resources, both hardware and software, of a computer. An OS
usually pre-define basic functionalities that are common to most applications
and provide such functionalities, such as file and device management, graphical
user interface rendering, and computer networking, to the applications that run
on that OS. This makes the development of application software easier and
faster. Examples of well known OSs
An operating system links you to your
programs (also called applications or software) and then links your programs to
the computer's hardware. It controls how the computer does its most basic tasks,
like storing files or talking to printers.
Microsoft Windows XP is an example of
an operating system. It uses graphics (pictures) to connect you to the
computer's hardware and software in an easy-to-understand (hopefully!) way.
Microsoft Windows XP also comes with many free, built-in programs that can help
you create documents, movies and images, calculate figures, enjoy some music,
browse the Internet, or play a few games.
The Software
While the OS is technically a software
program, it is distinct from other software specifically referred to as
"application software". Application software, we'll just call it
software, are programs that you install onto a PC that make the PC useful.
Software is a complex series of
instructions telling the computer what to do. The instructions are very
detailed because they have to tell the computer every single step to be
performed. For example a word processing program has instructions for what to
do when you press the letter "A". The software tells the computer to
take the letters as they are pressed on the keyboard, then it tells it to add
the letter to the letters you already typed and it tells the computer to
display the letter on the screen so you can see what you have typed. The
computer doesn't do anything without very explicit instructions.
1.2 Parts of a Personal
Computer
A personal computer is made up of many
components; called "hardware". This article briefly explains each
hardware component in turn. If you are interested only in a specific component,
use the list below to jump directly to that information.
A typical PC contains the following
hardware:
There are many other possible hardware
components, such as a DVD, CD-RW, Zip drive or network card. There are also
many subcomponents of a PC, such as the cooling fan, printer port or reset
switch to name a few. The hardware in the list above is nearly universal to a
basic PC.
While a PC is built up from hardware
components, the hardware is only half of the equation. The other vital part of
a PC is the software. Without software, the hardware is useless; and vice
versa.
The fundamental software for a PC is
called an "operating system". Without an operating system or
"OS", a PC can't do much. The operating system tells the components
of a PC what to do and when to do it. Windows, MAC OS, Linux and Unix are all
examples of operating System.
The Case
The case is the box that houses the
PC. All of the hardware, except for the peripherals, is housed inside the case.
There are two common styles of cases: "desktop" and "tower."
The desktop case usually sits under the monitor and is roughly the size of two
or three shoe boxes side by side. The tower case stands upright on one end and
is usually placed on the floor. Tower cases can be the same size as a desktop
case but often range up much larger. Another, less common, case style is the
"rack mount" case which slides in and out of an equipment rack.
The Power Supply
Where the power cord connects to the
back of the PC is the power supply. The power supply converts AC current from
the wall outlet to the appropriate DC voltages for the various components of
the computer.
The power supply has a fan built into
it to keep itself and the PC cool. Most PC's have at least one additional
cooling fan, often mounted directly on the CPU. The power supply or its
internal fan can wear out. Fortunately, the entire unit is easily replaced.
The Motherboard
The motherboard is the largest and
most fundamental component of a PC. Every other hardware component is somehow
attached to the motherboard. The motherboard is the common link for every
component to communicate and work together.
The motherboard has a series of slots,
sockets and connectors for connecting the various components of a PC. The
memory, accessory cards, and CPU are installed directly onto the motherboard in
most cases. The drives and peripherals communicate with the motherboard through
wired connections.
It is becoming increasingly common for
motherboards to integrate features that used to require separate accessory
cards. Most motherboards integrate drive controllers and communication ports;
and with greater frequency they integrate sound, video and network features as
well.There are a wide range of motherboards to choose from. They differ in
features, speed, capacity and the CPU supported. They also differ in size,
shape and layout, this is commonly referred to as the "form factor".
The CPU
The CPU, which stands for Central
Processing Unit, is the brain of the PC. It is often referred to as the
"processor" or "chip". The CPU directs, coordinates and
communicates with the hardware components and performs all of the
"thinking". What a CPU actually does is perform mathematical
calculations. It is the software that people write that translates those
calculations into useful functions for us.
The speed of the CPU, generally
speaking, is the number of calculations it can perform in one second. It is
more complicated than that, but it is a reasonable way to think of the speed. A
500 MHz (megahertz) CPU performs about 500,000,000 mathematical calculations
per second.
As the speed of new CPUs increase, the
difference is becoming less obvious to computer users. A CPU that is twice as
fast as another one will not result in a PC running twice as fast. The CPU has
to wait for other, slower components and for the user too. The CPU spends a lot
of time sitting idle, waiting for something to do.
CPUs have something called a
"cache" or memory cache. The memory cache is where information is
stored that the CPU is likely to need soon. This memory is in addition to the
normal memory installed in a PC. The difference is that the cache is built
right onto the CPU (and/or very near the CPU), and it is much faster than
conventional memory. Cache memory was developed to reduce the time the CPU had
to wait while information was retrieved from the standard memory.
The RAM Memory
The memory chips store information,
temporarily, for short term use. A PC's memory is an entirely different thing
from the hard disk "memory". The hard disk stores information
"permanently" for long term use.
A PC's memory only contains
information when the PC is on. When the PC is turned off, the information in
the memory chips disappears. The information in memory is similar to a thought,
it gets replaced when you start thinking about something else. Hard disk memory
is like writing down the information and storing it in a filing cabinet.
The Hard Disk Drive
A hard disk (also called a "hard
drive") is much like a filing cabinet. The programs and data are stored on
the hard disk and the computer accesses them as needed. When the computer
accesses the hard drive, it is reading the stored information into memory. That
memory is the temporary workspace. The original file on the hard disk is left
undisturbed. When the computer stores information, it writes the data to the
hard disk. That process results in the old file being replaced or modified with
the new information. If you save data to a new file, or install new software,
the information is written to the disk in an available, unused portion of the
disk.
The Floppy Disk Drive
The floppy disk drive is a device that
records data onto a removable storage disk called a floppy disk. Floppy disks,
also called "floppies", are the most basic storage medium for data.
However their limited capacity, typically 1.44 megabytes, makes them of limited
use.
A floppy disk can be used to copy
files from one PC to another PC or for making backup copies of files. Replacing
a floppy drive is very easy and inexpensive to do, should the need arise.
The CD-ROM
The CD-ROM drive is a device that
reads information or music off of a compact disk (CD). CD-ROM stands for
Compact Disc Read Only Memory. Most software is distributed on CDs because of
their low cost and large capacity (650MB or more).
The CD is spun at high speed inside
the drive while a laser is directed at the surface to read the data or music.
The CD-ROM speed is referenced as 12X or 12 speed (or any other number). This
simply means that it spins the CD that many times faster than the original
industry specification. So, a 48X CD-ROM spins the CD up to 48 times faster
than the original specification. Faster is better.
Many PCs are now built with a CD-RW
drive, which stands for Compact Disc, Read-Write. Unlike a standard CD-ROM, you
can write data onto a CD with a CD-RW drive. CD-R disks allow you to write to
the CD once and read it an unlimited number of times. With the use of
RE-writable CDs (CD-RWs) you can reuse the disk and rewrite over it again many
times.
The speeds of a CD-RW are expressed
like this, 4X 4X 32X. This means it can write to the CD up to 4 times the spec
speed, rewrite the CD up to 4 times spec speed and read the CD up to 32 times
the spec speed.
The Graphics Card or Video Card
The video adapter card or graphics
adapter translates information into graphics and text that appear on the
monitor screen.
The graphics adapter plugs into a slot
on the motherboard or is incorporated directly into the electronics of the
motherboard. Most motherboards now include a slot specifically designed for the
graphics adapter called the AGP slot (Advanced Graphics
Port
Modern graphics adapters usually
incorporate some memory right on the card to improve their performance. To
further improve the performance of the video output, a second graphics
accelerator card can be used in tandem with the graphics adapter.
The Sound Card
Most PCs are typically equipped for
multimedia. They can play sounds, music, and speech. The sound card processes
the information and outputs the signal to the speakers.
The sound card plugs into a slot on
the motherboard or is incorporated directly into the the motherboard. With a
basic sound card a microphone, speakers, joystick and an auxiliary sound source
can be connected to it. More advanced cards may offer additional input and
output features.
The Modem
The modem is a device that enables the
PC to use a telephone line to communicate with other PCs and devices. The name
comes from "MOdulation DEModulation".
The modem plugs into a slot on the
motherboard or is incorporated directly into the electronics of the
motherboard. It converts data into signals that can be transmitted over the
telephone line and receives data to convert back for the PC to use.
The Mouse
The mouse is a user input device that
enables you to communicate with your PC. By moving the mouse and pressing the
two or three buttons, you can highlight and select images on the screen to give
directions to your PC. Some mice offer a wheel to aid in the scrolling of a
window without having to move the mouse.
A mouse is usually connected by a wire
but wireless mice are also available. Wired mice may use a serial, PS/2 or a
USB port. Other variations of mice available include the trackball and
touchpad.
The mouse detects movement either as a
ball underneath the mouse rolls along your desk or by using a light inside the
mouse and measuring the reflection from the desktop.
The Keyboard
The keyboard is the primary user input
device. It enables you to communicate with your computer. While the mouse is
also a fundamental device to control the PC, the keyboard goes one step further
by allowing you to enter specific information as opposed to simply pointing and
clicking.
The keyboard connects to the computer
through a wire, although wireless keyboards are also available. Variations of
the classic keyboard include the addition of action specific buttons, most
commonly for Internet features, and split keyboards which angle the two halves
of the keyboard to reduce stress on your wrists as you type
1.3 SYSTEM BOARD
·
The
mother board is the main circuit board inside the PC, it holds the CPU and
memory, provides expansion slots for peripherals and whether directly or
indirectly connects to every part of the pc
·
A
motherboard also known as main board,system board or logic board,
BASIC PARTS OF MOTHER BOARD
·
Keyboard
port
·
Floppy
controller
·
IDE(Integrated
Drive Electronics)
·
Serial
and parallel communication port
·
Audio,video,modem,network
·
Chipsets
·
North
bridge
·
South
bridge
·
Cmos
battery
Keyboard port:
·
the
keyboard port mounted on the mother board
passes the instruction to central processing unit through chipset while
user is pressing the particular key on the key board
Floppy controller:
·
virtually
every PC made since 1992 has included the floppy controller on the mother board
·
in
earlier versions required a separate controller card that plugged into a ISA
slot
·
the
purpose of floppy controller is to control the process of floppy drive
Integrated Drive Electronics(IDE):
·
the
IDE interface was efficiently created in 1988 to replace older hard drive
standard called ST-506/412 interface
·
IDE
interface used to connects hard drive and CD drive
·
Virtually
every PC made since 1992 will include the IDE interface electronics on the
board
Serial and parallel communication
port:
- As with the floppy controller and IDE
interface, the serial and parallel port
have been proceeded on the motherboard from 1992.
- We need dual role header
connector to connect mother board to serial and parallel communication
port.
Audio,Video,Modem,Network,SCSI:
- These are the interface that have
been known to be mounted on the keyboard
- Usually these devices are best
installed as adapter cards. so that we can easily upgraded as advanced
technology bocomes available.
Chipsets:
- The chipset interact with all the hardware and the
software,determines software speed, and
handles all addressing functions for the cpu.
North bridge:
- The north bridge is the name
given to the systen controller chip.
- This the chip that directly
connect to the cpu in the front
side bus(FSB) to the high speed _ components of the software,like RAM
etc..
South bridge:
- The peripheral bus controller
known as south bridge, in the component of the chipset that is responsible
for interconnecting the cpu to the components of the software like USB port,
IDE port
- PC/XT - the original open motherboard
standard created by IBM for the first home computer, the IBM-PC. It
created a large number of clone motherboards due to its open
standard and therefore became the de facto
standard.
- AT form
factor (Advanced Technology) - the first form factor to gain
wide acceptance, successor to PC/XT. Also known as Full AT, it was popular
during the 386
era. Now obsolete, it is superseded by ATX.
- Baby AT - IBM's successor to the AT
motherboard, it was functionally equivalent to the AT but gained
popularity due to its significantly smaller physical size. It usually
comes without AGP port.
- ATX - the evolution of the Baby AT form factor, it is now
the most popular form factor available today.
- ETX,
used in embedded systems and single board computers.
- Mini-ATX - essentially the same as the ATX
layout, but again, with a smaller footprint.
- microATX - again, a miniaturization of the
ATX layout. It is commonly used in the larger cube-style cases such as the
Antec ARIA.
- FlexATX - a subset of microATX allowing more
flexible motherboard design, component positioning and shape.
- LPX
- based on a design by Western
Digital, it allows for smaller cases based on the ATX
motherboard by arranging the expansion cards in a riser (an
expansion card in itself, attaching to the side of the motherboard - image).
This design allows the cards to rest parallel to the motherboard as
opposed to perpendicular to it. The LPX motherboard
is generally only used by large OEM manufacturers.
- Mini LPX - a smaller subset of the LPX
specification.
- NLX - a low-profile motherboard, again
incorporating a riser, designed in order to keep up with market trends.
NLX never gained much popularity.
- BTX (Balanced Technology Extended) -
a newer standard proposed by Intel as an eventual successor to ATX.
- microBTX and picoBTX - smaller subsets of the BTX standard.
- Mini-ITX - VIA's highly integrated small
form factor motherboard, designed for uses including thin
clients and set-top boxes.
- WTX (Workstation Technology Extended) - a large
motherboard (more so than ATX) designed for use with high-power
workstations (usually featuring multiple processors or hard
drives.
While most desktop
computers use one of these motherboard form factors, laptop
(notebook) computers generally use highly integrated, customized and
miniaturized motherboards designed by the manufacturers. This is one of the
reasons that notebook computers are difficult to upgrade and expensive to
repair - often the failure of one integrated component requires the replacement
of the entire motherboard, which is also more expensive than a regular
motherboard due to the large number of integrated components in it.
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