Computer harware complete notes

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INTRODUCTION TO COMPUTER STRUCTURE & FUNCTIONALITY:
Let us start us with a term Computer

COMPUTER stands for:

C-common
o-operating
m-machine
p-particularly
u-used for
t-technical
e-education and
r-research

Display Devices

A computeris a computing device made up of many distinct electronic components that all function
together in order to accomplish some useful task (such as adding up the numbers in a spreadsheet or
helping you write a letter). By this definition, note that we’re describing a computer as having many
distinct parts that work together.. Each component has a very specific function.

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Now we will learn how to identify computer components, includingthe following:

Motherboards Storage devices

Power supplies Display devices

Input devices Adapter cards

Ports and cables Processors

Memory

Any PC is a complex machine. It could be described as a melting pot of various technologies and products,
manufactured by a host of companies in many different countries. This diversity is a great advantage
because it gives the PC its versatility. However, these components don’t always “melt” together into a
unified whole without the help of a technician. The different products—whether they’re hard disks,
modems, sound cards, or memory boards—must share one processor and one motherboard and therefore
must be designed to work in harmony.

The whole computer system is categorized into four main components:

INPUT DEVICES :( Keyboard, mouse, scanner, joystick, Digital camera)

Central Processing Unit :( Control Unit, Arithmetic and Logical Unit)

MEMORY :( Primary and Secondary memory)

OUTPUT DEVICES :( Monitor, Printer, plotter, speakers)

Introduction to computer peripherals:
Input devices: All devices those helps us to sent commands and data to the computer such as

Keyboard :-keyboard is easily the most popular input device, so much so that its popularity is more
of a necessity. The keys on a keyboard complete individual circuits when each one is pressed. The
completion of each circuit leads to a unique scan code that is sent to the keyboard connector on
the computer system. The computer uses a keyboard controller chip to interpret the code as the
corresponding key sequence. The computer then decides what action to take based on the key
sequence and what it means to the computer and the active application.

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Mouse:-Computer mouse was born in the 1970s at Xerox’s Palo Alto Research Center (PARC), it
was Apple in 1984 that made the mouse an integral part of the personal computer image with the
introduction of the Macintosh. Many variations of the mouse exist, including:-
trackballs, tablets, touchpads, and pointing sticks.The mouse today can be
wired to the computer system or wireless. Wireless versions use batteries to
power them, and the optical varieties deplete these batteries more quickly
thantheir mechanical counterparts.

Mechanical Mouse Optical Mouse
The motion-detection mechanism of the original technologies used optical receptors to catch LED light
mouse was a simple ball that protruded from the reflected from specially made surfaces purchased with
bottom of the device so that when the bottom the devices and used like a mouse pad. A mouse pad is
was placed against a flat surface that offered a a special surface to improve mechanical mouse
slight amount of friction, the mouse would glide traction while offering very little resistance to the
over the surface, but the ball would roll, actuating mouse itself. As optical science advanced for the
two rollers that mapped the linear movement to mouse, lasers were used to allow a sharper image to
the software interface. be captured by the mouse and more sensitivity in
motion detection.

Bar-code Reader:A bar-code reader (or bar-code scanner) is a specialized input device commonly
used in retail and other industrial sectors that manage inventory. Bar-code readers can use LEDs or
lasers as light sources and can scan one- or two-dimensional bar-codes. Bar-code readers can
connect to the host system in a number of ways, but serial connections, such as RS-232 and USB are
fairly common. The scanner converts all output to keyboard scans so that the system treats the
input as if it came from a keyboard. For certain readers, wireless communication with the host is
also possible, using IR, RF, Bluetooth, Wi-Fi, and more.
Touch Screens:Touch-screen technology converts stimuli of some sort, which are generated by
actually touching the screen, to electrical impulses that travel over serial connections to the
computer system. These input signals allow for the replacement of both the keyboard and the
mouse. However, standard computer systems are not the only application for touch-screen
enhancement. This technology can also be seen in PDAs, point-of-sale venues for such things as PIN
entry and signature capture, handheld and bar-mounted games, ATMs, remote controls,
appliances, and vehicles. For touch screens there are a handful of solutions for how to convert a
touch to a signal. Some less-successful ones rely on warm hands, sound waves, or dust-free
screens. The more successful screens have optical or electrical sensors that are quite a bit less
fastidious. In any event, the sensory system is added onto a standard monitor at some point in the
creation of the monitor.
Scanner:-scanner is a device that optically scans images, printed text, handwriting, or an object, and
converts it to a digital image.

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Microphone:-is an acoustic-to-electric transducer or sensor that converts sound into an electrical
signal. In 1876, Emile Berliner invented the first microphone used as a telephone voice transmitter.
Microphones are used in many applications such as telephones, tape recorders, hearing aids,
motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio
and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for
non-acoustic purposes such as ultrasonic checking or knock sensors.

Output Devices:-

Display Devices:
CRT (Cathode ray tube) LCD (Liquid Cristal display) Plasma Display
In a CRT, a device called Two major types of LCDs are used in laptops They are called "plasma" displays
an electron gun shoots today: active matrix screens and passive because the pixels rely on plasma
electrons toward the matrix screens. cells, or what are in essence chambers
back of the monitor Passive matrix A passive matrix screen uses more commonly known as fluorescent
screen . The back of the a row of transistors across the top of the lamps. A panel typically has millions of
screen is coated with screen and a column of them down the side. tiny cells in compartmentalized space
special chemicals It sends pulses to each pixel at the between two panels of glass. These
(called phosphors) that intersections of each row and column compartments, or "bulbs" or "cells",
glow when electrons combination, telling it what to display. hold a mixture of noble gases and a
strike them. This beam Passive matrix displays are becoming minuscule amount of mercury. Just as
of electrons scans the obsolete because they’re less bright and in the fluorescent lamps over an office
monitor from left to have poorer refresh rates and image quality desk, when the mercury is vaporized
right than active matrix displays. However, they and a voltage is applied across the
use less power than active matrix displays cell, the gas in the cells form a plasma.
do. With flow of electricity (electrons),
some of the electrons strike mercury
Active matrix An active matrix screen uses a particles as the electrons move
separate transistor for each individual pixel through the plasma, momentarily
in the display, resulting in higher refresh increasing the energy level of the
rates and brighter display quality. These molecule until the excess energy is
screens use more power, however, because shed. Mercury sheds the energy as
of the increased number of transistors that ultraviolet (UV) photons. Varying the
must be powered. Almost all notebook PCs voltage of the signals to the cells thus
today use active matrix. A variant called allows different perceived colors.
thin-film transistor (TFT) uses multiple
transistors per pixel, resulting in even better
display quality.

Display systems convert computer signals into text and pictures and display them on a televisionlike
screen. Several different types of computer displays are used today, including the TV.Ways of measuring a
monitor’s image quality: dot pitch and refresh (scan) rate. A monitor’s dot pitch is the distance between
two dots of the same color on the monitor. Usually given in fractions of a millimeter (mm), it tells how
sharp the picture is. The lower the number, the closer together the pixels are, and thus the sharper the
image. An average dot pitch is 0.28mm. A monitor’s refresh rate specifies how many times in one second
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the scanning beam of electrons redraws the screen. The phosphors stay bright for only a fraction of a
second, so they must constantly be hit with electrons to stay lit. Given in draws per second, or hertz (Hz),
the refresh rate specifies how much energy is being put into keeping the screen lit. Most people notice a
flicker in the display at refresh rates of 75Hz or lower because the phosphors begin to decay to black
before they’re revived; increasing the refresh rate can help reduce eyestrain by reducing the flickering. The
resolution of a monitor is the number of horizontal and vertical pixels that are displayed. Most monitors
allow for two or more resolutions, and you can pick the one to use in the desktop settings of the operating
system. The vertical hold (V-hold) settings can be tweaked to make the image appear properly in the
monitor.

Display System Problems:-

There are two types of video problems: no video and bad video. No video means no image appears on the
screen when the computer is powered up. Bad video means the quality is substandard for the type of
display system being used.

Connector Types:
The following are common connector types: DB A D-shaped connector with a metal ring around a set of
pins. Named for the number of pins/holes used: DB-25, DB-9, DB-15, and so on. Can be either parallel or
serial. Common uses: VGA video, legacy serial devices such as external modems, and parallel printer cables
(the connector on the PC only; the printer end uses Centronics).

RJ Registered jack : a plastic plug with small metal tabs, like a telephone
cord plug. Numbering is used in the naming: RJ-11 has two metal tabs, and
RJ-14 has four. Both are used for telephone systems. RJ-45 has eight tabs
and is used for Ethernet 10BaseT/100BaseT networking. Always serial.

BNC Stands for Bayonet:-Neill Connector or British Naval Connector. A metal wire
surrounded by shielding, like a cable television connector. Used for 10Base2 Ethernet
networking. Always serial.

Centronics:A plastic block with metal tabs flat against it, surrounded by a D-shaped metal ring. Used to
connect a parallel printer cable to the printer, and also for some SCSI devices. Always parallel.

Ribbon connector:A rectangular block consisting of a set of square holes that connect to pins on a
circuit board. Used to connect floppy drives, IDE drives, and some SCSI devices to their controllers.
Always parallel.

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PS/2 (mini-DIN)A round connector with six small pins inside, commonly used to connect keyboards on
ATX motherboards or PS/2 style mice.

DIN:A larger round connector with five rather large pins inside, used for connecting the keyboard on an
AT motherboard.

USB:A flat rectangular connector, used with USB interfaces.

Cabling:

Cables are used to connect two or more entities together. They’re usually constructed of several wires
encased in a rubberized outer coating. The wires are soldered to modular connectors at both ends. These
connectors allow the cables to be quickly attached to the devices they connect. Cables may be either
shielded or unshielded. This refers to shielding against electromagnetic interference (EMI); it has nothing
to do with whether the cable is shielded against dirt or water. A is given in The F or M in a connector’s
designation is for female (holes) or male (pins). Common PC Cable list of common cable types used in
PCs, their descriptions, their maximum effective lengths, and their most common uses

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Fans: When you turn on a computer, you will often hear lots of whirring. Contrary to popular opinion, the
majority of the noise isn’t coming from the hard disk (unless it’s about to go bad). Most of this noise is
coming from the various fans inside the computer. Fans provide airflow within the computer.

Introduction to printers:

Impact Printers: The most basic type of printer is the category known as impact printers . Impact printers,
as their name suggests, use some form of impact and an inked ribbon to make an imprint on the paper. In
a manner of speaking, typewriters are like impact printers. Both use an inked ribbon and an impact head to
make letters on the paper. The major difference is that the printer can accept input from a computer.
There are two major types of impact printers: daisy wheel and dot matrix. Each type hasits own service and
maintenance issues.

Dot-Matrix Printers: The other type of impact printer we’ll discuss is thedot-matrix printer. These printers
workin a manner similar to daisy-wheel printers, but instead of a spinning, character-imprinted wheel, the
print head contains a row of pins

(short, sturdy stalks of hard wire). These pins are triggered in patterns that form letters and numbers as

the print head moves across the paper

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Bubble-Jet Printers:

The next category of printer technology is one of the most popular in use today. This category is actually an
advanced form of an older technology known asinkjet printers. Both types of printers spray ink on the
page, but inkjet printers used a reservoir of ink, a pump, and an inknozzle to accomplish this. They were
messy, noisy, and inefficient. Bubble-jet printers workmuch more efficiently and are much cheaper.In
abubble-jet printer,bubbles of ink are sprayed onto a page and form patterns thatresemble the items being
printed. In this section, you will learn the parts of a bubble-jet printer, as well as how bubble-jet printers
work.

Laser Printers:Laser printers and inkjet printers are referred to as page printers because they receive their
print job instructions one page at a time (rather than receiving instructions one line at a time). There are
two major types of page printers: those that use the electro photographic (EP) print process and those that
use the light-emitting diode (LED) print process. Each works in basically the same way, with slight
differences.

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Print head/Ink Cartridge:

The first part of a bubble-jet printer is the one people see the most: the print head. This part of a printer
contains many small nozzles (usually 100–200) that spray the ink in small dots onto the page. Many times
the print head is part of the ink cartridge, which contains a reservoir of ink and the print head in a
removable package. Color bubble-jet printers include multiple print heads, one for each of the CMYK print
inks (cyan, magenta, yellow, and black).

Daisy-Wheel Printers:
Although they aren’t really covered on the A+ exam, the first type of impact printer we’re going to
discuss is the Daisy-wheel printer. These printers contain a wheel (called the
because it looks like a daisy) with raised letters and symbols on each “petal” (see Figure 7.1). When the
Printer needs to print a character; it sends a signal to the mechanism that contains the wheel. This
Mechanism is called the printheaddaisy wheel. The printhead rotates the daisy wheel until the required
character is in place. An electromechanical hammer (called a ) then strikes the back of the petal Containing
the character. The character pushes up against an inked ribbon that ultimately strikes The paper, making the
impression of the requested character.

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Introduction to motherboard and all its components:

Motherboards:
The motherboard is the backbone of a computer. The components of the motherboard provide basic
services needed for the machine to operate and provide a platform for devices such as the processor,
memory, disk drives, and expansion devices. For this objective, you should study the types of
motherboards, their ports and memory, the types of CPU sockets, and the types of expansion slots.

Components on a motherboard:

System Board Form Factors:

Form factor refers to the size and shape of a component. There are four popular motherboard form factors
for desktop PCs: AT, ATX, BTX, and NLX.

AT ”AT” is an older style of motherboard. A slightly more modern variant of it is the baby AT, which is
similar but smaller. Its key features are a two-piece power-supply connector, ribbon cables that connect
the I/O ports to the board, and an AT-style keyboard connector. The expansion slots are parallel to the
wide edge of the board.

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ATX:Most system boards today use the ATX form factor. It contains many design improvements over the
AT, including I/O ports built directly into the side of the motherboard, the CPU positioned such that the
power-supply fan helps cool it, and the ability for the PC to be turned on and off via software. It uses a
PS/2 style-connector for the keyboard. The expansion slots are parallel to the narrow edge of the board.

BTX the Balanced Technology Extended (BTX) motherboard was designed by Intel to deal with issues
surrounding ATX (heat, power consumption, and so on). The BTX motherboard is larger than ATX, so there
is more room for integrated components; there is also an optimized airflow path and a low-profile option.
Although the standard has been around for a number of years, it isn’t expected to become popular in the
market until at least 2007.

NLXAn acronym for New, Low profile extended, this form factor is used in low-profile case types. It
incorporates expansion slots that are placed on a riser board to accommodate the reduction in case size.
However, this design adds another component to troubleshoot.

Buses: A bus is a set of signal pathways that allows information and signals to travel between components
inside or outside a computer. A motherboard has several buses, each with its own speed and width.

The external data bus, also called the system bus, connects the CPU to the chipset. On modern systems, it’s
64-bit. The address bus connects the RAM to the CPU. On modern systems, it’s 64-bit. The expansion bus
connects the I/O ports and expansion slots to the chipset. There are usually several different expansion
buses on a motherboard. Expansion buses can be broken into two broad categories: internal and external.
Internal expansion buses include Industry Standard Architecture (ISA), Peripheral Component Interconnect
(PCI), and Accelerated Graphics Port (AGP); they’re for circuit boards. External expansion buses include
serial, parallel, Universal Serial Bus (USB), FireWire, and infrared. The following sections explain some of
the most common buses.

ISA: This is a 16-bit bus (originally 8-bit on the oldest computers) that operates at 8MHz. Its slots are
usually black. New motherboards may not have this type of slot, because the ISA bus is old technology and
is being phased out. Besides the slow speed and narrow width, another drawback of the ISA bus is that
each ISA device requires separate system resources, including separate Interrupt Requests (IRQs). In a
heavily loaded system, this can cause an IRQ shortage. (PCI slots, in contrast, can share some resources.)

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PCI

The PCI bus is a fast (33MHz), wide (32-bit or 64-bit) expansion bus that is the modern standard in
motherboards today for general-purpose expansion devices. Its slots are typically white. PCI devices can
share IRQs and other system resources with one another in some cases. All modern motherboards have at
least three PCI slots. Figure 1.6 shows some PCI slots.

AGP

As systems got faster, PC game players wanted games that had better graphics, more realism,and more
speed. However, as the computers got faster, the video technology couldn’t seem tokeep up, even with
the PCI bus. The AGP bus was developed to meet this need.The AGP slot is usually brown, and there is only
one. It’s a 32-bit or 64-bit bus, and it runsvery fast (66MHz or faster). It’s used exclusively for the video
card. If you use a PCI video card, the AGP slot remains empty.

PCIE

PCI Express (PCIE , PCI-E, or PCIe) uses a network of serial interconnects that operate at highspeed. It’s
based on the PCI system; most existing systems can be easily converted to PCIE.Intended as a replacement
for AGP and PCI, PCIEhas the capability of being faster than AGP,while maintaining the flexibility of PCI.
There are currently six different speed levels and theycorrespond to AGP speeds: 1X, 2X, 4X, 8X, 16X, and
32X.

AMR AND CNR

Audio Modem Riser (AMR) was originally created to speed manufacturing (and certification) by separating
the analog circuitry (modem and analog audio) onto its own card. Over time,this has been replaced by CNR
(CommunicationsNetwork Riser), which includes the capabilitiesof AMR and allows the motherboard
chipset to be designed with additional integratedfeatures

.

Identifying Purposes and Characteristics of Adapter Cards

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An adapter card (also known as an expansion card) is simply a circuit board you install into a computer to
increase the capabilities of that computer. Adapter cards come in many different kinds, but the important
thing to note is that no matter what function a card has, the card being installed must match the bus type
of the motherboard you are installing it into (for example, you can install a PCI network card only into a PCI
expansion slot). Five of the most common expansion cards that are installed today are as follows:

_ Video card

_ Network interface card (NIC)

_ Modem

_ Sound card

_ I/O card

Video Card

A video adapter (more commonly called a video card) is the expansion card you put into a computer in
order to allow the computer to display information on some kind of monitor or LCD display. A video card
also is responsible for converting the data sent to it by the CPU into the pixels, addresses, and other items
required for display. Sometimes, video cards can include dedicated chips to perform certain of these
functions, thus accelerating the speed of display. With today’s

motherboards, most video cards are AGP and, with increasing popularity, PCIe expansion cards that fit in
the associated slot on a motherboard. Figure 1.51 shows an example of an AGP-based video card.

A video expansion card

Network Interface Card (NIC)

A network interface card (NIC) is an expansion card that connects a computer to a network so that it can
communicate with other computers on that network. It translates the data from the parallel data stream
used inside the computer into the serial data stream of packets used on the network. It has a connector for
the type of expansion bus on the motherboard (PCIe, PCI, ISA, and so on) as well as a connector for the
type of network (such as RJ-45 for UTP or BNC for coax). In addition to the NIC, you need to install software
or drivers on the computer in order for the computer to use the network.

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A network interface card (NIC)

Modem

Any computer that connects to the Internet using a dial-up connection needs a modem. A modem is a
device that converts digital signals from a computer into analog signals that canbe transmitted over phone
lines and back again. These expansion card devices have one connector for the expansion bus being used
(PCIe, PCI, ISA, and so on) and another for connection to the telephone line. there are two RJ-11 ports: one
for connection to the telephone line and the other for connection to a telephone. This is the case primarily
so that putting a computer online still lets someone hook a phone to thatwall jack (although he won’t be
able to use the phone while the computer is connected to the Internet).

AN INTERNAL MODEM

Sound Card

Just as there are devices to convert computer signals into printouts and video information, there are
devices to convert those signals into sound. These devices are known as sound cards. Many different
manufacturers make sound cards, but the standard has been set by Creative Labs with its SoundBlaster

series of cards.

I/O Card

I/O card is often a catchall phrase for any adapter card that expands the system to interface with devices
that offer input to the system, output from the system, or both. Common examples of I/ O are the serial
and parallel ports of the system, drive interface connections, and so on. A very popular expansion card of
the 1980s and early 1990s was known as the Super I/O card. This one adapter had the circuitry for two
standard serial ports, one parallel port, two PATA controllers, and one floppy controller. Some versions
included more still. For many years, if you wanted to use a SCSI hard drive in your system, you had to
install an adapter card that expanded the motherboard’s capabilities to allow the use of SCSI hard drives.
The drives would them cable to the adapter, and the adapter would perform the requisite conversion of
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the drive signals to those that the motherboard and the circuits installed on it could use. Today, common
I/O adapter cards tend to be USB 2.0 adapters and FireWire adapters

Understanding Printer and

Scanner Fundamentals

There are several different types of printers and scanners available on the market today. In this section,
you will learn about the different types of printers and scanners that you will see as a technician, their
basic components, and how they function.

LEGACY PARALLEL AND SERIAL

These buses are called legacy because they’re old technology and are being phased out. Thelegacy serial
port, also called an RS-232 port, is a 9-pin or 25-pin male connector. It sends dataone bit at a time and is
usually limited to about 115Kbps in speed.The legacy parallel port transfers data 8 bits at a time. It’s a 25-
pin female connector. A systemtypically has only one parallel port, but because many printers are now
coming with USBinterfaces, this is no longer the inconvenience that it used to be.

USB

USB is a newer expansion bus type that is used almost exclusively for external devices. Allmotherboards
today have at least two USB ports. Some of the advantages of USB include hotpluggingand the capability
for up to 127 USB devices to share a single set of system resources.USB 1.1 runs at 12Mbps, and USB 2.0
runs at 480Mbps. Because USB is a serial interface, itswidth is 1 bit.

IEEE 1394/FIREWIRE

Some newer motherboards have a built-in IEEE 1394/FireWire port, although this port ismore typically
found on a PCI expansion board. It transfers data at 400Mbps and supports upto 63 chained devices on a
single set of resources. It’s hot pluggable, like USB. Figure 1.8shows the connections on a FireWire card.

Daughterboard

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(“daughters” of the “mother”). A common use is to insert one daughterboard (also calledAny boards added
to the motherboard to expand its capabilities are known as daughterboardsdaughter boards) into the
motherboard and allow expansion cards to then be inserted into itsideways, thus saving space.

On-Motherboard Cache

On older motherboards, the L2 cache is on its own RAM-like stick made of very fast static randomaccess
memory (SRAM). It’s known as cache on a stick (COAST). On newer systems, theL2 cache is built into the
CPU packaging.Some newer systems also have an L3 cache, which is an external cache on the motherboard
that sits between the CPU and RAM.

IDE and SCSI On-Motherboard Interfaces

Most motherboards include two Integrated Drive Electronics (IDE) channels but don’t includebuilt-in Small
Computer System Interface (SCSI). A consideration when choosing a motherboard for IDE is that it needs to
support the desired level of UltraDMA to match the capabilities of thehard drive you want to use.

Chipsets

The chipset is the set of controller chips that monitors and directs the traffic on the motherboardbetween
the buses. It usually consists of two or more chips. Motherboards use two basicchipset designs: the
north/south bridge chipset and the hub chipset.North/south bridge is the older of the two. The north
bridge connects the system bus to theother relatively fast buses (AGP and PCI). The south bridge connects
ISA, IDE, and USB. Athird chip, SuperIO, connects the legacy parallel and serial ports.The hub chipset
includes a memory controller hub (equivalent to the north bridge), an I/Ocontroller hub (equivalent to the
south bridge), and a SuperIO chip.

CMOS

You can adjust a computer’s base-level settings through a Basic Input/Output System (BIOS)Setup program,
which you access by pressing a certain key at startup, such as F1 or Delete(depending on the system).
Another name for this setup program is CMOS Setup. The mostcommon settings to adjust in CMOS include

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port settings (parallel, serial, USB), drive types,boot sequence, date and time, and virus/security
protections.

ACCESSING CMOS SETUP

Your PC keeps these settings in a special memory chip called the Complementary MetallicOxide
Semiconductor (CMOS) chip. The CMOS chip must have a constant source of powerto keep its settings. To
prevent the loss of data, motherboard manufacturers include a smallbattery to power the CMOS memory.
On modern systems, this is a coin-style battery, about

the same diameter of a dime and about 1/4 inch thick.You can press a certain key or group of keys to
access the setup program during the poweron self-test (POST). This utility allows you to change the
configuration through a group ofmenus. There are many different CMOS Setup programs, depending on
the BIOS make andmanufacturer, so it’s impossible to provide specifics here; instead, we’ll look at
capabilities.

LOAD SETUP DEFAULTS

The purpose of this setting is to configure the PC back to the default settings set by the factory.If you make
changes to your settings and the machine becomes disabled, in most cases, selectingthis menu item
returns the machine to a usable state. You may then try different settingsuntil you achieve your desired
configuration. This is an important setting to know aboutbefore making any other changes.

DATE AND TIME

One of the most basic things you can change in CMOS Setup is the system date and time. Youcan also
change this from within the operating system.

CPU SETTINGS

In most modern systems, the BIOS detects the CPU’s type and speed automatically, so anyCPU setting in
CMOS Setup is likely to be read-only.

MEMORY SPEED/PARITY

Most systems today detect the RAM amount and speed automatically. Some motherboardscan use
different types of RAM, such as parity and nonparity, or different speeds, and theCMOS Setup program

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may provide the opportunity to change those settings. Increasingly,however, RAM is becoming a read-only
part of CMOS Setup programs.

POWER MANAGEMENT

The Power Management settings determine the way the PC will act after it has been idle forcertain time
periods. For example, you may have choices like Minimum, Maximum, and UserDefined. The Minimum and
Maximum settings control the HDD Off After, Doze Mode,Standby Mode, and Suspend Mode settings with
predefined parameters. If you select UserDefined, you must manually configure these settings to your
personal preferences.

Northbridge

The Northbridge subset of a motherboard’s chipset is the set of circuitry or chips that performs one very
important function: management of high-speed peripheral communications. The Northbridge subset is
responsible primarily for communications with integrated video using AGP and PCIe, for instance, and
processor-to-memory communications. Therefore, it can be said that much of the true performance of a
PC relies on the performance of the Northbridge

chipset and the communications between it and the peripherals it controls.

Southbridge

The Southbridge chipset, as mentioned earlier, is responsible for providing support to the myriad onboard
peripherals (PS/2, Parallel, IDE, and so on), managing their communications with the rest of the computer
and the resources given to them. Most motherboards today have integrated PS/2, USB, Parallel, and Serial.
Some of the optional features handled by the Southbridge include LAN, audio, infrared, and FireWire (IEEE
1394). When first integrated, the quality of onboard audio was marginal at best, but the latest offerings
(such as the AC97 audio chipset) rival Creative Labs in sound quality and number of features (even
including Dolby Digital Theater Surround technology). The Southbridge chipset is also responsible for
managing communications with the other expansion buses, such as PCI, USB, and legacy buses

A typical motherboard chipset

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Introduction to processors.
Processor/CPUs
The central processing unit (CPU) is a processor chip consisting of
an array of millions of integratedcircuits. Its purpose is to accept,
perform calculations on, and eject numeric data. It’sconsidered
the “brain” of the computer because it’s the part that performs the mathematicaloperations required for
all other activity.

There are two form factors for CPU chips: pin grid array (PGA) and single edge contact cartridge(SECC). The
PGA style is a flat square or rectangular ceramic chip with an array of pinsin the bottom. The actual CPU is
a tiny silicon wafer embedded inside that ceramic chip. TheSECC style is a circuit board with the silicon
wafer mounted on it. The circuit board is thensurrounded by a plastic cartridge for protection; the circuit
board sticks out of the cartridge

along one edge. This edge fits into a slot in the motherboard.All CPUs today require cooling because they
generate heat as they operate. The cooling canbe either active or passive. A passive heat sink is a block of
heat-conductive material that sitsclose to the CPU and wicks away the heat into the air. An active heat sink
contains a fan thatpulls the hot air away from the CPU.

External Speed (Clock Speed)

The clock speed, or external speed, is the speed at which the motherboard communicates withthe CPU. It’s
determined by the motherboard, and its cadence is set by a quartz crystal (the systemcrystal) that
generates regular electrical pulses.

Internal Speed

The internal speed is the maximum speed at which the CPU can perform its internal operations.This may be
the same as the motherboard’s speed (the external speed), but it’s morelikely to be a multiple of it. For
example, a CPU may have an internal speed of 1.3GHz butan external speed of 133MHz. That means for
every tick of the system crystal’s clock, the CPUhas 10 internal ticks of its
own clock.

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Cache Memory

A cache is an area of extremely fast memory used to store data that is waiting to enter or exitthe CPU. The
Level 1 cache, also known as the L1 or front-side cache, holds data that is waitingto enter the CPU. On
modern systems, the L1 cache is built into the CPU. The Level 2cache, also known as the L2 or back-side
cache, holds data that is exiting the CPU and is waitingto return to RAM. On modern systems, the L2 cache
is in the same packaging as the CPUbut on a separate chip. On older systems, the L2 cache was on a
separate circuit board installedin the motherboard, and was sometimes called COAST.

The Bus

The processor’s ability to communicate with the rest of the system’s components relies onthe supporting
circuitry. The system board’s underlying circuitry is called the bus. The computer’sbus moves information
into and out of the processor and other devices. A bus allowsall devices to communicate with each other.
The motherboard has several buses. The externaldata bus carries information to and from the CPU and is
the fastest bus on the system.The address bus typically runs at the same speed as the external data bus
and carries datato and from RAM. The PCI, AGP, and ISA interfaces also have their own buses with
theirown widths and speeds.The CPU must be compatible with the motherboard in the following ways:

Physical connectivity The CPU must be in the right kind of package to fit into the motherboard.

Speed The motherboard’s chipset dictates its external data-bus speed; the CPU must be capableof
operating at that external speed.

Instruction set The motherboard’s chipset contains an instruction set for communicatingwith the CPU; the
CPU must understand the commands in that set. For example, a motherboarddesigned for an AMD Athlon
CPU can’t accept an Intel Pentium CPU, because theinstruction set is different.

Voltage The CPU requires that a certain voltage of power be supplied to it via the motherboard’sinterface.
This can be anywhere from +5V for a very old CPU down to around +2.1Vfor a modern one. The wrong
voltage can ruin the CPU.

There are several ways of differentiating one CPU from another. The following sectionsexplain
specifications according to type, speed, voltage, and cache memory.

CPU Speed

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The CPU’s speed is the frequency at which it executes instructions. This frequency is measuredin millions of
cycles per second, or megahertz (MHz); or billions of cycles per second, or gigahertz(GHz).The CPU has an
internal and an external speed. The external speed corresponds with themotherboard’s speed, based on its
system crystal. The system crystal pulses, generating acadence at which operations occur on the
motherboard. Each pulse is called a clock tick. The

CPU’s internal speed is usually a multiple of that, so that multiple operations occur internallyper clock tick.
A CPU’s speed as described in its specifications is its internal speed.

CPU Cache

Each CPU has at least two caches: L1 and L2. The L1 cache is built into the CPU on modernsystems. It’s the
front-side cache, where data waits to enter the CPU. The L2 cache, or backsidecache, is where data exiting
the CPU waits. On modern systems, the L2 cache is withinthe CPU’s packaging but not integrated into the
CPU’s die. On older systems, the L2 cache wason a separate set of chips on the motherboard. You can
compare one CPU to another according

to the size of its L1 and L2 caches.On some CPUs, the L2 cache operates at the same speed as the CPU; on
others, the cachespeed is only half the CPU speed. Chips with full-speed L2 caches have better
performance.Some newer systems also have an L3 cache, which is external to the CPU. It sits betweenthe
CPU and RAM to optimize data transfer between them.

CPU Voltage

A CPU’s voltage is the amount of electricity provided to it by the motherboard. Older CPUs havehigher
voltages (around +5V); newer ones have lower voltages (less than +2V in some cases).One reason a given
motherboard can’t support many different CPUs is that it must providethe correct voltage. To get around
this issue, some motherboards have voltage regulator modules(VRMs) that are able to change the voltage
based on the CPU.

CPU Manufacturers

The market leader in the manufacture of chips is Intel Corporation, with Advanced MicroDevices (AMD)
gaining market share in the home PC market. Other competitors includeMotorola and IBM.

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Introduction to memory and storage devices.
Memory
To pass the A+ exam and be a productive computer technician, you
must be familiar withmemory. Not only will you be tested on this
subject, but one of the most common upgradesperformed on a PC
is adding memory. Adding memory is a simple task, but before you
can addmemory you must have the correct type. When we say
memory, we are most often referring to Random Access Memory
(RAM). However, there are other types of memory. We’ll
discussthem all in this section. Be familiar with the various types
and their usage.

Physical Memory

Physically, memory is a collection of integrated circuits that store data and program informationas patterns
of 1s and 0s (on and off states) in the chip. Most memory chips require constantpower (also called a
constant refresh) to maintain those patterns of 1s and 0s. If poweris lost, all those tiny switches revert back
to the off position, effectively erasing the data frommemory. Some memory types, however, don’t require
a refresh.There are many types of RAM. In this section, we examine each type in detail.

SRAM

Static RAM (SRAM) stores whatever is placed in it until it’s changed. Unlike dynamic RAM(DRAM), it
doesn’t require constant electrical refreshing. Another name for it is nonvolatileRAM (NVRAM). It’s
expensive, so it isn’t typically used for the main memory in a system.

DRAM

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DRAM is an improvement over SRAM. DRAM uses a different approach to storing the 1s and0s. Instead of
using transistors, DRAM stores information as charges in very small capacitors.If a charge exists in a
capacitor, it’s interpreted as a 1. The absence of a charge is interpretedas a 0.Because DRAM uses
capacitors instead of switches, it needs to use a constant refresh signalto keep the information in memory.
DRAM requires more power than SRAM for refresh signalsand, therefore, is mostly found in desktop
computers.DRAM technology allows several memory units, called cells, to be packed to a high
density.Therefore, these chips can hold very large amounts of information. Most PCs today use

DRAM of one type or another.

Let’s take a brief look at some of the different types of DRAM:

Fast page mode (FPM) An older type of RAM (almost always 72-pin SIMM packaging) thatisn’t
synchronized in speed with the motherboard. It’s rated in nanoseconds of delay, withlower numbers being
better (for example, 60ns). FPM is now obsolete.

Extended data out (EDO) Like FPM, an older type of RAM, usually in 72-pin SIMM form.It performs a bit
better than normal FPM RAM because it needs to be refreshed less frequently.Like FPM, it’s now obsolete.

Synchronous DRAM (SDRAM)Synchronized to the speed of the motherboard’s systembus. Synchronizing
the speed of the systems prevents the address bus from having to wait forthe memory because of different
clock speeds. SDRAM typically comes in the form of 168-pinDIMMs or 184-pin RIMMs.

Double data rate (DDR) SDRAM/DDR2 Essentially, clock-doubled SDRAM. The memorychip can perform
reads and writes on both sides of any clock cycle (the up, or start, and thedown, or ending), thus doubling
the effective memory executions per second. So, if you’reusing DDR SDRAM with a 100MHz memory bus,
the memory will execute reads and writesat 200MHz and transfer the data to the processor at 100MHz.
The advantage of DDR overregular SDRAM is increased throughput and thus increased overall system
speed. The next generation of DDR SDRAM is DDR2 (double data rate 2). This allows for twoaccesses per
clock cycle and effectively doubles the speed of the memory.

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Various memory module form factors

RAMBUSA relatively new and extremely fast (up to 800MHz) technology that uses, for themost part, a new
methodology in memory system design. RAMBUS (also known as directRambus) is a memory bus that
transfers data at 800MHz. RAMBUS memory models (oftencalled Rambus inline memory modules
[RIMMs]), like DDR SDRAM, can transfer data onboth the rising and falling edges of a clock cycle. That
feature, combined with the 16-bit busfor efficient transfer of data, results in the ultra-high memory
transfer rate (800MHz) and thehigh bandwidth of up to 1.6GBps.

Memory Chip Package Types

Memory chips come in many different types of packages. The ones most frequently encounteredare
discussed in the following sections.

DUAL INLINE PACKAGE (DIP)

Dual inline package (DIP) memory is so named because the individual RAM chips use the DIPstylepackage
for the memory module. Older computers, such as the IBM AT, arranged thesesmall chips like rows of
caskets in a small memory “graveyard.” This type of memory has longbeen obsolete.

SIMMS

Single inline memory modules (SIMMs) were developed because DIPs took up too much realestate on the
logic board. Someone got the idea to put several DIP chips on a small circuitboard and then make that
board easily removable.
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Each of these RAM circuit boards is a stick of RAM. There are two sizes of SIMMs: 30-pinand 72-pin. The
30-pin are older, 8-bit sticks. The 72-pin are 32-bit sticks. Figure 1.10 showsone of each. SIMMs are called
single because they’re single-sided. When you count the numberof pins (the metal tabs) along the bottom,
there are 30 or 72 of them. In contrast, DIMMs(dual inline memory modules) are double-sided; for
example, a 168-pin DIMM has 84 pins oneach side. DIMMS

AND RIMMSDIMMs are double-sided memory chips used in modern systems (Pentium and higher).
Theytypically have 168 pins and are 64 bits in width. Figure 1.11 shows a DIMM.A RIMM is just like a
DIMM, except it’s a Rambus DRAM stick, has 184 pins, and isslightly longer in size.

SODIMMS AND MICRODIMMS

Portable computers (notebooks and subnotebooks) require smaller sticks of RAM because of their smaller
size. Two types are small outline DIMM (SoDIMM) and MicroDIMM.

RAM Banks and Bit Width

As explained earlier, 30-pin SIMMs are 8-bit, 72-pin SIMMs are 32-bit, and DIMMs are 64-bit. The
motherboard has an address bus that carries data from the RAM to the CPU andchipset. It has a certain
width. On Pentium and higher systems, it’s 64-bit; on earlier systems,it’s 32-bit (386 and 486) or less (286
and below). A bank of RAM is a single stick or a groupof sticks where the collective bit width adds up to the
width of the address bus. For example, on a Pentium motherboard, a single bank consists of a single 64-bit
DIMMor a pair of two 32-bit SIMMs. For a 486 motherboard, a single bank is a single 32-bit SIMMor four 8-

bit SIMMs.

Video RAM

Video memory (also called video RAM [VRAM]) is used to store image data for processing bythe video
adapter. The more video memory an adapter has, the better the quality of image thatit can display. Also,
more VRAM allows the adapter to display a higher resolution of image.

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Introduction to
storage devices:

Storage Devices

Storage media hold the data being accessed, as
well as the files the system needs to operate
anddata that needs to be saved. The various types
of storage differ in terms of capacity, accesstime,
and the physical type of media being used.

Hard-Disk Systems

Hard disks reside inside the computer (usually) and can hold more
information than otherforms of storage. The hard-disk system contains
three critical components: the controller, thehard disk, and the host
adapter. The controller controls the drive, the hard disk provides
aphysical medium to store the data, and the host adapter is the
translator.

Floppy Drives: A floppy disk drive (referred to by CompTIA as FDD) is a magnetic storage medium that
usesa floppy disk made of thin plastic enclosed in a protective casing. The floppy disk itself (orfloppy, as it’s
often called) enables the information to be transported from one computer toanother easily. The
downside of a floppy disk drive is its limited storage capacity. Floppy disksare limited to a maximum
capacity of 2.88MB, but the most common type of floppy in usetoday holds only 1.44MB. Table 1.1 lists the
various floppy disks and their capacity. All ofthese except the 1.44MB-capacity model are obsolete, and it
isn’t far behind.

CD-ROM Drives: CD-ROM stands for Compact Disc Read-Only Memory. The
CD-ROM is used for long-termstorage of data. CD-ROMs are read-only,
meaning that once information is written to a CD,it can’t be erased or
changed. Access time for CD-ROMs is considerably slower than for a
harddrive. CDs normally hold 650MB of data and use the ISO 9660 standard, which allows themto be used
in multiple platforms.

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Zip Drives and Jazz Drives

Iomega’s Zip and Jaz drives are detachable, external hard disks that are
used to store a large volume (around 100MB for the Zip, 1GB and 2GB
for the Jaz) of data on a single, floppy-sized disk. The drives connect to
either a parallel port or a special interface card. The major use of Zip and
Jaz drives is to transport large amounts of data from place to place. This
used to be accomplished with several floppies.

Tape Backup Devices

Another form of storage device is the tape backup. Tape backup devices can be
installed internally or externally and use a magnetic tape medium instead of disks
for storage. They hold much more data than any other medium but are also much
slower. They’re primarily used for archival storage.

Optical Drives

Optical drives work by using a laser rather than magnetism to change the characteristics of the storage
medium.

Flash Drives (and SD Cards)

Flash drives have been growing in popularity for years and replacing
floppy disks due to their capacity and small size. Flash is ideally suited for
use not only with computers, but also withmany other things—digital
cameras, MP3 players, and so on.

Thumb Drives

Thumb drives are USB flash drives that have become extremely popular for transporting files.

External Hard Drives

A number of vendors are now making external hard drives. These often connect to
the computerthrough the USB port, but can also connect through the network (and
be shared by otherusers) or other connections. While some are intended for
expansion, many are marketed forthe purpose of “mirroring” data on the internal
drive(s) and often incorporate a push-buttonswitch that starts a backup.

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Introduction to ports, slots, connectors and
power supply

Peripheral Ports and Connectors

In order for a computer to be useful and have the most
functionality, there must be a way to get the data into and out of it. Many different ports are available for
this purpose. We will discuss the different types of ports and how they work later in this chapter. Briefly,
the seven most common types of ports you will see on a computer are serial, parallel, Universal Serial Bus
(USB), video, Ethernet, sound in/out, and game ports.

AT System Connectors

The next type of power connector is called the AT system connector. There are two 6-wire connectors,
labeled P8 and P9 (as shown in Figure 1.39). They connect to an AT-style motherboard and deliver the
power that feeds the electronic components on it. These connectors have small tabs on them that
interlock with tabs on the motherboard’s receptacle. If there are two connectors, you must install them in
the correct fashion. To do this (on most systems), place the connectors side by side with their black wires
together, and then push the connectors onto the receptacle on the motherboard.

Floppy drive power connector

AT power supply system board connectors

A standard peripheral power connector ATX power connector

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ATX12V P4 power connector

SATA power connector

Other Types of Ports

A few other ports are used with computers today. These ports include the following:

_ Universal Serial Bus (USB)

_ IEEE 1394 (FireWire)

_ Infrared

_ Audio jacks

_ PS/2 (mini-DIN)

_ Centronics

Universal Serial Bus (USB)

Most computers built after 1997 have one or more flat ports in place of one DE9M serial
port. These ports are Universal Serial Bus (USB) ports, and they are used for connecting
multiple (up to 127) peripherals to one computer through a single port (and the use of
multiport peripheral hubs). USB version 1.1 supported data rates as high as 12Mbps
(1.5MBps). The newest version, USB 2.0, supports data rates as high as 480Mbps (60MBps).

PS/2 (Keyboard and Mouse)

Another common port, as mentioned earlier, is the PS/2 port. A PS/2 port (also known as a
mini-DIN 6 connector) is a mouse and keyboard interface port first found on the IBM PS/2
(hence the name). It is smaller than previous interfaces (the DIN-5 keyboard port and serial
mouse connector), and thus its popularity increased quickly.

and mouse, respectively, imprinted next to the ports.

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Centronics

The last type of port connector is the Centronics connector, a micro
ribbon connector named for the Wang subsidiary that created it. It
has a unique shape. It consists of a central connection bar
surrounding by an outer shielding ring. The Centronics connector
was primarily used in parallel printer connections and SCSI
interfaces. It is most often found on

peripherals, not on computers themselves (except in the case of
some older SCSI interface cards).

Power Supplies

The device in the computer that provides the power is the
power supply. A power supply converts 110-volt AC current into
the voltages a computer needs to operate. On an AT
motherboard,these are +5 volts DC, –5 volts DC, +12 volts DC,
and –12 volts DC. Components inmodern PCs don’t use the
negative voltages; they’re provided for backward
compatibilityonly. On an ATX motherboard, an additional
voltage is provided: +3.3 volts DC.Power-supply problems are
usually easy to troubleshoot. The system doesn’t respond inany way when the power is turned on. When
this happens, open the case, remove the powersupply, and replace it with a new one.Be aware that
different cases have different types of on/off switches. The process of replacinga power supply is a lot
easier if you purchase a replacement with the same mechanism.Even so, remember to document exactly
how the power supply was connected to the on/offswitch before you remove it.Power supplies contain
transformers and capacitors that carry lethal amounts of current.

They aren’t meant to be serviced. Do not attempt to open them or do any work on them. shows a generic
power supply.

A power supply has a rated output capacity in watts, and when you fill a system withpower-hungry devices,
you must make sure that maximum capacity isn’t exceeded. Otherwise,problems with power can occur,
creating lockups or spontaneous reboots.To determine the wattage a device draws, multiply voltage by
current. For example, if adevice uses 5 amps of +3.3V and 0.7 amps of +12V, a total of 25 watts is
consumed. Do thiscalculation for every device installed. Most devices have labels that state their power
requirements.Some devices don’t have power labels

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Estimating Power Consumption

Motherboard 20–30 watts

CPU 30–70 watts (faster CPU, more watts)

AGP video card 20–50 watts

PCI circuit boards 5 watts each

ISA circuit boards 10 watts each

Floppy drive 5 watts

CD drive 10–25 watts

RAM 8 watts per 128MB

IDE hard drive 5–15 watts

SCSI hard drive 10–40 watts

Principles of Laptops and Portable Devices:
Whether you choose to call them laptops, portable devices, or something different is mostly a matter of
semantics. This objective tests your knowledge of some of the basic operations of laptops. In many cases,
the components are the same as in a desktop computer, and they were discussed in Chapter 1. Those that
are different are focused on here.

Critical Information

A portable computer must provide all the functionality of a desktop
counterpart yet be able to withstand travel, run in the absence of AC
power, and be much smaller and more compact. When you get right
down to it, there is not a great deal of difference between laptop and
desktop computers, with the exception that laptops are more difficult
to disassemble and form factors on items such as motherboards,
memory, and hard drives become important. While they perform the

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same functions, size is critical. Laptop-specific elements are discussed in the following sections.

Laptops vs. Desktops

If you’ve ever shopped for a laptop, you have no doubt noticed that the prices of desktop PCs are often
quite a bit lower than for notebook computers, yet they are faster and more powerful. If you’ve ever
wondered what makes a laptop so much different than a PC, here are the primary differences between
laptops and desktops:

Portability

This is probably the most obvious difference. Laptops are designed to be portable. They run on batteries,
so you aren’t tied to one spot at home or at the office. Networking options are available that allow you to
connect to a network wirelessly and do work from just about anywhere, including malls, airports,
Starbucks, and so on. As anyone who’s tried to

bring their full-tower PC to a LAN party can tell you, desktops just aren’t that portable.

Cost

Laptops cost more—sometimes as much as 60 to 80 percent more—than
desktop computerswith similar features. The primary reason is that
portability requires small componentsand unique proprietary designs for
those components so they fit into the small size necessary.Miniature
versions of components cost more money than standard-size (desktop)
versions.

Performance

By and large, laptops are always going to lose out somewhere in the
performance department. Compromises must often be made
between performance and portability, and considering that portability
is the major feature of a laptop, performance is what usually suffers.
While it is possible to have a laptop with comparable performance to a desktop, the amount of money one
would have to spend for a “desktop replacement” laptop is considerable. This is not to say that a laptop
can’t outperform a desktop, it’s just that the “bang for the buck” factor is higher in a desktop.

A laptop motherboard

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A desktop hard drive compared to a laptop hard drive

144-pin SoDIMM

Understanding Operating Systems
Computers are pretty much useless without software. A piece of hardware makes a good paperweight or
doorstop, unless you have an easy way to interface with it. Software is that interface. While there are
many types of software, or programs, the most important application you’ll ever deal with is the operating
system. Operating systems have many different, complex functions, but two of them jump out as being
critical: one, interfacing with the hardware, and two, providing a platform on which other applications can
run. Here are three major distinctions of software to be aware of:

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Introduction to Operating System.
Operating System (OS)

Provides a consistent environment for other software to execute commands.
The OS gives users an interface with the computer so they can send commands (input) and receive
feedback or results (output). To do this, the OS must communicate with the computer hardware to
perform the following tasks:

Disk and file management

Device access

Memory management

Output format

What’s in a Window?

We have now looked at the nature of the Desktop, the Taskbar, the Start menu, and icons. Each of these
items was created for the primary purpose of making access to user applications easier, and these
applications are in turn used and managed through the use of windows, the rectangular application
environments for which the Windows family of operating systems is named. We will now examine how
windows work and what they are made of. A program window is a rectangular area created on the screen
when an application is opened within Windows. This window can have a number of different forms, but
most windows include at least a few basic elements.

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Windows Versions

Windows 1

Version 1 of Windows featured the tiling windows, mouse support, and menu systems that still drive next-
generation OSs such as Windows 98, Windows CE, and Windows 2000

Windows 2

Version 2, released in 1987, added icons and allowed application windows to overlap each other, as well as
tile. Support was also added for PIFs (program information files), which allowed the user to configure
Windows to run their DOS applications more efficiently

Windows 3.x

Windows 3.0 featured a far more flexible memory model, allowing it to access more memory than the
640KB limit normally imposed by DOS. It also featured the addition of the File Manager and Program
Manager, allowed for network support, and could operate in 386 Enhancedmode

Windows 95

Although it dominated the market with its DOS operating system and its add-on Windows interface,
Microsoft found that the constraints of DOS were rapidly making it difficult to take full advantage of rapidly
improving hardware and software developments

Windows 98/Me/NT/2000/XP

After Windows 95, Windows 98 was introduced as its successor, followed by Windows Me (Millennium
Edition). Windows 98/Me is still a very common PC OS to find on users’ computers, but XP is even more
common yet.

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Windows Vista& window 7: Scheduled to launch in early 2007, Windows Vista (formerly code-named
Longhorn) is the newest operating system platform developed by Microsoft. It will be presented in five
different versions: Business, Enterprise, Home Premium, Home Basic, and Ultimate.

The Command Prompt: Although we’re talking about the Windows operating system in this book, its
ancestor, the Microsoft Disk Operating System (MS-DOS), still plays a role in Windows today. MS-DOS was
never meant to be extremely friendly. Its roots are in CP/M, which, in turn, has its roots in Unix. Both of
these older OSs are command line–based, and so is MS-DOS. In other words, they all use long strings of
commands typed in at the computer keyboard to perform operations. Some people prefer this type of
interaction with the computer, including many folks with technical backgrounds (such as yours truly).
Although Windows has left the full command-line interface behind, it still contains a bit of DOS, and you
get to it through the command prompt.

The Registry: Windows configuration information is stored in a special configuration database known as
the Registry. This centralized database contains environmental settings for various Windows programs. It
also contains registration information that details which types of file extensions are associated with which
applications. So, when you double-click a file in Windows Explorer,the associated application runs and
opens the file you double-clicked. The Registry is broken down into a series of separate areas called hives.
These keys are divided into two basic sections—user settings and computer settings. In Windows 2000 and
XP, a number of files are created corresponding to each of the different hives. Most of these

files do not have extensions, and their names are system, software, security, sam, and default. One
additional file that does have an extension is NTUSER.DAT.

The basic hives of the Registry are these:

HKEY_CLASSES_ROOT: Includes information about which file extensions map to particular applications.

HKEY_CURRENT_USER: Holds all configuration information specific to a particular user, such as their
Desktop settings and history information.

HKEY_LOCAL_MACHINE: Includes nearly all configuration information concerning the actual computer
hardware and software.

HKEY_USERS: Includes information about all users who have logged on to the system. The
HKEY_CURRENT_USER hive is actually a subkey of this hive.

HKEY_CURRENT_CONFIG: Provides quick access to a number of commonly needed keys that are otherwise
buried deep in the HKEY_LOCAL_MACHINE structure.

Virtual Memory
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Another thing you may need to configure is virtual memory. Virtual memory uses what’s called a swap file,
or paging file. A swap file is actually hard-drive space into which idle pieces of programs are placed, while
other active parts of programs are kept in or swapped into main memory. The programs running in
Windows believe that their information is still in RAM, but Windows has moved the data into near-line
storage on the hard drive. When the application needs the information again, it is swapped back into RAM
so that it can be used by the processor.

Windows System Files: Among the things you must be familiar with in preparation for the A+ exam are the
startup and system files used by Windows 2000 and Windows XP. We will look at each of them individually,
but Windows makes nosing around in the startup environment difficult, and so there is a change you need
to make first.

Key Boot Files: Windows 2000 and XP require only a few files, each of which performs specific tasks:
NTLDR Bootstraps the system. In other words, this file starts the loading of an OS on thecomputer.
BOOT.INI Holds information about which OSs are installed on the computer.

BOOTSECT.DOS: In a dual-boot configuration, keeps a copy of the DOS or Windows 9x boot sector so that
the Windows 9x environment can be restored and loaded as needed.

NTDETECT.COM:Parses the system for hardware information each time Windows 2000/XP is loaded. This
information is then used to create dynamic hardware information in the Registry.

NTBOOTDD.SYS:On a system with a SCSI boot device, used to recognize and load the SCSI interface. On
EIDE systems, this file is not needed and is not even installed.

NTOSKRNL.EXE The Windows 2000/XP OS kernel:System Files In addition to the previously listed files, all
of which except NTOSKRNL.EXE are located in the root of the C: partition on the computer, Windows
2000/XP needs a number of files from its system directories (e.g., system and system32), such as the
hardware abstraction layer (HAL.DLL). Numerous other DLL (dynamic link library) files are also required,
but usually the lack or corruption of one of them produces a noncritical error, whereas the absence of
HAL.DLL

causes the system to be nonfunctional.

System Files Configuration Tools in Windows 2000/XP
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The MSCONFIG system-configuration tool that was available in Windows 9x doesn’t exist in Windows 2000.
It is, however, included with Windows XP.

Disk Management

Where there are files, there are disks. That is to say, all the files and programs we’ve talked about so far
reside on disks. Disks are physical storage devices, and these disks also need to be managed. There are
several aspects to disk management. One is concerned with getting disks ready to be able to store files and
programs. Another deals with backing up your data. Yet another involves checking the health of disks and
optimizing their performance. We’ll look at these aspects in more detail.

Backing Up the Data on Your Drives

Another very important aspect of disk management is backing up the data on your drives. Sooner or later,
you can count on running into a situation where a hard drive fails or data becomes corrupted. Without a
backup copy of your data, you’re facing a world of trouble trying to re-create the data, if that’s even
possible or economically feasible. You also shouldn’t rely on the Recycle Bin. Although it is a good utility to
restore an occasional file or directory that a user has accidentally deleted, it will not help you if your drives
and the data on them become unusable.

File Management

file management is the process by which a computer stores data and retrieves it from storage. Although
some of the file-management interfaces across Windows interfaces may have a different look and feel, the
process of managing files is similar across the board.

Files and Folders

For a program to run, it must be able to read information off the disk and write information backto the
disk. In order to be able to organize and access information—especially in larger new systems that may
have thousands of files—it is necessary to have a structure and an ordering process.

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Introduction to basic troubleshooting of
computer Hardware & Software.
Basic Aspects of Troubleshooting

Although everyone approaches troubleshooting from a different perspective, a few things should remain
constant. Among them is a basic appreciation for data. Any hardware component can be replaced, but data
often can’t be. For that reason, it’s important to always perform backups before making any changes.

Basic Diagnostic Procedures

Step 1: Define the Problem

If you can’t define the problem, you can’t begin to solve it. You can define the problem by asking questions
of the user. Here are a few questions to ask the user to aid in determining what the problem is, exactly:

Step 2: Check the Simple Stuff First

This step is the one that most experienced technicians overlook. Often, computer problems are the result
of something simple. Technicians overlook these problems because they’re so simple that the technicians
assume they couldn’t be the problem.

Step 3: Check to See If It’s User Error

This error is common but preventable. The indication that a problem is due to user error is when a user
says he can’t perform some very common computer task, such as printing or saving a file. As soon you hear
these words, you should begin asking questions to determine if it’s simply a matter of teaching the user the
correct procedure. A good question to ask following his statement of the problem is, “Were you ever able
to perform that task?” If he answers no to this question, it means he’s probably doing the procedure
wrong. If he answers yes, you must move on to another set of questions.

Step 4: Restart the Computer

It’s amazing how often a simple computer restart can solve a problem. Restarting the computer clears the
memory and starts the computer with a clean slate.

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Step 5: Determine If the Problem Is Hardware or Software Related

This step is important because it determines on what part of the computer you should focus your
troubleshooting skills. Each part requires different skills and different tools.

Step 6: If the Problem Is Hardware Related, Determine Which Component Is Failing

Hardware problems are pretty easy to figure out. If the modem doesn’t work, and you know it isn’t a
software problem, the modem is probably the piece of hardware that needs to be replaced.

Step 7: Check Service Information Sources

As you may (or may not) have figured out by now, we’re fond of old sayings. Another old sayingapplies
here: “If all else fails, read the instructions.” The service manuals are your instructions for troubleshooting
and service information.

Step 8: If It Ain’t Broke …

When doctors take the Hippocratic oath, they promise to not make their patients any sicker than they
already were. Technicians should take a similar oath. It all boils down to “If it ain’t broke, don’t fix it.

Step 9: Ask for Help

If you don’t know the answer, ask one of your fellow technicians. They may have run across the problem
you’re having and know the solution.

POST Routines

Every computer has a diagnostic program built into its BIOS called the power-on self-test(POST). When you
turn on the computer, it executes this set of diagnostics. Many steps areinvolved the POST, but they
happen very quickly, they’re invisible to the user, and they vary

among BIOS versions. The steps include checking the CPU, checking the RAM, checking for the presence of
a video card, and so on. The main reason to be aware of the POST’s existence is that if it encounters a
problem, the boot process stops. Being able to determine at what point the problem occurred can help you
troubleshoot.

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Applying Basic Troubleshooting Techniques

Identifying Motherboard and CPU Problems

Identifying I/O Ports and Cables

Identifying Cooling Issues

Identifying Case Issues

Identifying Hard-Disk System Problems

Identifying Display Device Problems

Identifying Floppy and Other Removable Disk-Drive Problems

Identifying Sound Card Problems

Identifying CD-ROM/DVD Issues

Identifying NIC Issues

The Technical Zone

Computer harware complete notes

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Computer harware complete notes