A system unit is the main body of a desktop computerA system unit is the main body of a desktop computer, typically consisting of a metal or (rarely) plastic enclosure containing the motherboard, power supply, cooling fans,

l d k d d h d l dinternal disk drives, and the memory modules and expansion cards that are plugged into the motherboard, such as videoand network cards.

Sometimes called : the chasis

What are common components inside theWhat are common components inside the system unit?

MemoryProcessor

yAdapter cards

Sound cardVid dVideo card

Drive baysPower supplyPower supply

What is the motherboard?M i i it b dMain circuit board of the system unitContainsContains expansion slots, processor chipsprocessor chips, and memory slotsAlso called systemAlso called system board

What is a chip?S ll i f i d ti t i l hi hSmall piece of semi-conducting material on which integrated circuits are etched

Integrated circuits contain many microscopic pathways capable of carryingIntegrated circuits contain many microscopic pathways capable of carrying electrical current

Chips are packaged so they can be attached to a circuit board

What is the central processing unit (CPU)?

ProcessorProcessorControl Control

UnitUnitArithmetic Arithmetic

Logic Unit (ALU)Logic Unit (ALU)Arithmetic Arithmetic

Logic Unit (ALU)Logic Unit (ALU)

Interprets and carries out basic instructions that operate a computer

Control Control UnitUnitUnitUnit Logic Unit (ALU)Logic Unit (ALU)Logic Unit (ALU)Logic Unit (ALU)that operate a computer

InstructionsInstructionsDataData

UnitUnit

Control unit directs and coordinates operations in

InputInput OutputOutputMemoryMemoryDataData InformationInformation

InformationInformationcomputerArithmetic logic unit (ALU) performs

DevicesDevices DevicesDevicesMemoryMemoryDataData InformationInformation

InstructionsInstructions

(ALU) performs arithmetic, comparison, and logical operations

Al ll d th

StorageStorage

DataDataInformationInformation

Also called the processor

StorageStorageDevicesDevices

What is a machine cycle?F ti f th CPU i hi l

Step 1. FetchObtain program instruction

Four operations of the CPU comprise a machine cycle

or data item from memory

MemoryStep 2. DecodeStep 4. Store

Processor

Control UnitALU

Translate instruction into commands

pWrite result to memory

Control UnitALUStep 3. ExecuteCarry out command

What is pipelining?P b i f t hi d i t ti b fProcessor begins fetching second instruction before completing machine cycle for first instructionRes lts in faster processingResults in faster processing

What is a register?T hi h d t th t h ldTemporary high-speed storage area that holds data and instructions

Stores location Stores location from where instruction from where instruction

was fetchedwas fetchedStores Stores

i t ti hil it ii t ti hil it iStores data Stores data

hil ALUhil ALUinstruction while it is instruction while it is being decodedbeing decoded

while ALU while ALU computes itcomputes it

Stores results Stores results Sto es esu tsSto es esu tsof calculationof calculation

What is the system clock?Controls timing of all computer operationsControls timing of all computer operationsGenerates regular electronic pulses, or ticks, that set operating pace of components of system unit

Pace of systemPace of system

Each tick Each tick is a is a

Pace of system Pace of system clock is clock is clock speedclock speed

Most clock speeds are Most clock speeds are in the gigahertz (GHz) in the gigahertz (GHz)

Processor speed can Processor speed can also be measured in also be measured in illi f i t tiilli f i t ticlock cycleclock cycle

g g ( )g g ( )range (1 GHz = one range (1 GHz = one

billion ticks of system billion ticks of system clock per second)clock per second)

millions of instructions millions of instructions per second (MIPS)per second (MIPS)

p )p )

What are dual-core and multi-core processors?A d l i i l hi th t t i tA dual-core processor is a single chip that contains twoseparate processorsA multi-core processor is a chip with two or moreseparate processorsseparate processorsEach processor on a dual-core/multi-core chip generallyruns at a slower clock speed, but increase overall performance

What are the guidelines for selecting a processor?processor?

Wh h i k hWhat are heat sinks, heat pipes, and liquid cooling?

Heat sink—component with fins that cools processorHeat pipee—smaller p pdevice for notebook computersLiquid cooling—uses a continuous flow of fluids to transfer heat away

What is parallel processing?processing? Control ProcessorControl Processor

Using multiple processors

Processor 1Processor 1 Processor 2Processor 2 Processor 3Processor 3 Processor 4Processor 4

processors simultaneously to execute a program faster

MemoryMemory MemoryMemory MemoryMemory MemoryMemoryfasterRequires special software to divide problem and bringproblem and bring results together

Results combined

How do computers represent data?M t t di it l

Recognize only two discrete

Most computers are digital

states: on or offUse a binary system to recognize two statesUse Number system with two unique digits: 0 and 1, called bits(short for binary digits)

What is a byte?Ei ht bit d t th itEight bits grouped together as a unitProvides enough different combinations of 0s and 1s to represent 256 individual charactersto represent 256 individual characters

NumbersUppercase

52pp

and lowercase lettersPunctuation

54

marksOther 69

What are three popular coding systems to represent data?

ASCII—American Standard Code for Information InterchangeEBCDIC—Extended Binary Coded Decimal Interchange CodeUnicode—coding scheme capable of representing allUnicode coding scheme capable of representing allworld’s languages

ASCII Symbol EBCDIC00110000 0 1111000000110001 1 1111000100110001 1 1111000100110010 2 1111001000110011 3 11110011

How is a letter converted to binary form and back?

Step 2.An electronic signal for the capital letter T is sent to the

Step 1.The user presses the capital letter T(SHIFT+T key) on

system unit.(SHIFT+T key) on the keyboard.

T

Step 3.The system unit converts the Step 4.

Af i h biy

scan code for the capital letter Tto its ASCII binary code (01010100) and stores it in memory for processing.

After processing, the binary code for the capital letter T is converted to an image, and displayed on the output device. y p g

What is memory?Electronic components that storeElectronic components that store instructions, data, and resultsConsists of one or more chips onmore chips on motherboard orother circuit boardEach byte storedEach byte stored in unique location called an address, similar to seats in a concert hallsimilar to seats in a concert hall

How is memory measured?B b f b t il bl f tBy number of bytes available for storage

Term Abbreviation Approximate SizeKilobyte KB or K 1 thousand bytesMegabyte MB 1 million bytesg y yGigabyte GB 1 billion bytesTerabyte TB 1 trillion bytes

What is random access memory (RAM)?

Memory chips that can be Memory chips that can be read from and written read from and written

Also calledAlso called Most RAM is Most RAM is

to by processorto by processor

Also called Also called main memory main memory

or primary or primary storagestorage

volatile, it is lost volatile, it is lost when computer’s when computer’s

power is power is turned offturned off

The more RAM a The more RAM a computer has thecomputer has the

turned offturned off

computer has, the computer has, the faster it respondsfaster it responds

How do program instructions transfer in and out of RAM?Step 1 Wh t t th t t iRAM Step 1. When you start the computer, certain operating system files are loaded into RAM from the hard disk. The operating system displays the user interface on the screen.

Operating system Operating system instructionsinstructions

Operating system Operating system interfaceinterface

St 2

RAM

Web browser Web browser instructionsinstructions

Web browser Web browser windowwindow

Step 2. When you start a Web browser, the program’s instructions are loaded into RAM from the hard disk. The Web browser window is displayed on the screen.

Paint program Paint program instructionsinstructions

Paint program Paint program windowwindow

Step 3. When you start a paint program, the program’s instructions are loaded into RAM from the hard disk. The paint program, along with the Web Browser and certain operating system instructions are in RAM The paint programinstructionsinstructions windowwindow instructions are in RAM. The paint program window is displayed on the screen.

Step 4. When you quit a program, such as the RAM

Web browser programWeb browser program Web browserWeb browser

Web browser, its program instructions are removed from RAM. The Web browser is no longer displayed on the screen.

Web browser program Web browser program instructions are instructions are

removed from RAMremoved from RAM

Web browser Web browser window is no longer window is no longer

displayed on displayed on desktopdesktop

What are two basic types of RAM chips?

Do not have toDo not have tobe rebe re--energizedenergized

ftft

Most Most commoncommon

Static Static RAMRAM as often asas often as

DRAMDRAM

common common typetype

RAM RAM (SRAM)(SRAM)

Must beMust be Faster and Faster and Dynamic Dynamic RAMRAMMust be Must be rere--energized energized

constantlyconstantly

more reliable more reliable than DRAM than DRAM

chipschips

RAM RAM (DRAM)(DRAM)

Newer Type: Magnetoresistive RAM (MRAM)

Where does memory reside?

dual inline memory module

reside?Resides on small circuit board called memory moduleM l tMemory slots on motherboard hold memory modules

memory chip

memory slot

modules

How much RAM does an application require?D d th t fDepends on the types of software you plan to useuseFor optimal performance youperformance, you need more than minimum specificationsminimum specifications

How much RAM do you need?D d t f li ti i t d tDepends on type of applications you intend to runon your computer

RAM 512 MB 1 1 GB 2 GB 2 GB dRAM

Use

512 MB to 1 GB

1 GB to 2 GB 2 GB and up

•Home and businessusers managing

•Users requiring more advanced multimedia capabilities

•Power users creating professional Web sitesg g

personal finances•Using standard

application software

p•Running number-intensive

accounting, financial, orspreadsheet programs

p•Running sophisticated

CAD, 3D design, orother graphics-intensive

such as word processing

•Using educational or entertainment

•Using voice recognition•Working with videos, music, and

digital imaging•Creating Web sites

software

or entertainmentCD-ROMs

•Communicating with others on the Web

•Creating Web sites•Participating in video

conferences•Playing Internet gamesg g

What is cache?Helps speed computer processes by storing frequently used instructions and dataHelps speed computer processes by storing frequently used instructions and dataAlso called memory cache

L1 cache built into processorL2 cache slower but has larger capacityg p yL2 advanced transfer cache is faster, built directly on processor chipL3 h i t fL3 cache is separate from processor chip on motherboard (L3 is only on computers that use L2 advanced transfer cache)

What is read-only memory (ROM)?

Memory chips that store Memory chips that store permanent data permanent data

d i t tid i t ti

Nonvolatile memoryNonvolatile memory, it is not , it is not lost when computer’s lost when computer’s

power is turned offpower is turned offand instructionsand instructions power is turned offpower is turned off

Three types:Three types: EEPROM EEPROM (electrically(electricallyFirmwareFirmware——Manufactured with Manufactured with permanently writtenpermanently written

(electrically (electrically erasable programmable erasable programmable

readread--only memory)only memory)——Type of PROM Type of PROM

containing microcodecontaining microcodePROM PROM permanently written permanently written data, instructions, data, instructions, or informationor information

containing microcode containing microcode programmer programmer

can erasecan erase(programmable (programmable

readread--only only memory)memory)——

Blank ROM Blank ROM chip onto which chip onto which a programmer a programmer

can write permanentlycan write permanently

What is flash memory?N l til th t b d l t i ll d ittNonvolatile memory that can be erased electronically and rewritten

Used with PDAs, smart phones, printers, digital cameras, automotive

Step 1.Purchase and download music tracks from a W b it With d f i l bl

Step 3.Plug the headphones into the portable media player, push a button on the

devices, audio players, digital voice recorders, and pagers

Web site. With one end of a special cable connected to the system unit, connect the other end to the USB port in the portable media player.

portable media player, and listen to the music through the headphones.

flash memory chips

USB port

Step 2.Instruct the computer to copy the music tracks to the flash memory chip in the portable media player MP3 Playerthe flash memory chip in the portable media player.

What is CMOS?

Complementary metal oxide

Used in some RAM chips, flashmetal-oxide

semiconductor memory

RAM chips, flash memory chips, and

other types of memory chips

Uses battery Stores date,

memory chips

ypower to retain

information when other power is

,time, and

computer’s startupother power is

turned offstartup

information

What is access time?Amount of time it takes processorAmount of time it takes processor to read data from memory

Measured in nanoseconds (ns), ( ),one billionth of a second

It takes 1/10 of a second to blink your eye; a computer can perform up to 10 million operations in same amount of time

Term SpeedMillisecond One-thousandth of a secondMicrosecond One-millionth of a secondNanosecond One-billionth of a secondPicosecond One-trillionth of a second

What is an adapter card?E h t it id ti tEnhances system unit or provides connections to external devices called peripheralsAlso called an e pansion cardAlso called an expansion card

What is an expansion slot?A i k tAn opening, or socket, on the motherboard that can hold anthat can hold an adapter cardWith Plug and PlayWith Plug and Play, the computer automaticallyautomatically configures cardsand other devices as you install them

What are flash memory cards, PC cards, and ExpressCard modules?

An ExpressCard module adds memory, storage, sound, fax/modem, communications, and other capabilities to notebook computers

A flash memory card allows users to transfer data yfrom mobile devices to desktop computers

USB Flash driveAn PC card adds various capabilities to pcomputers

What are ports and connectors?Port connects external devices to system unitPort connects external devices to system unitConnector joins cable to peripheral

Available in one of two genders: male and female

What are different types of connectors?

What is a serial port?T it bit f d t tTransmits one bit of data at a timeConnects slow speed devicesConnects slow-speed devices, such as mouse, keyboard, modemmodem

What is a parallel port?C t d i th tConnects devices that can transfer more than one bit at a time such as a printera time, such as a printer

What are USB ports?

USB (universal serial bus) port can connect up to 127 different peripherals together

USB (universal serial bus) port can connect up to 127 different peripherals togetherup to 127 different peripherals together

with a single connector typeup to 127 different peripherals together

with a single connector type

Third USB device connects to second USB

Third USB device connects to second USB

Single USB port can be used to attach

Single USB port can be used to attach

PCs typically have six to eight USB ports

PCs typically have six to eight USB ports

to second USB device, and so onto second USB

device, and so on

Second USBSecond USB

be used to attach multiple peripherals

in a daisy chain

be used to attach multiple peripherals

in a daisy chain

on front or back of the system unit

on front or back of the system unit

Second USB device connects

to first USB device

Second USB device connects

to first USB deviceFirst USB

device connectsFirst USB

device connectsdevice connects to USB port on computer

device connects to USB port on computer

USB 2.0

What are FireWire ports?C t lti l t f d i th t iConnects multiple types of devices that require faster data transmission speedsAllows you to connect up to 63 devices togetherAllows you to connect up to 63 devices together

What are special-purpose ports?Allow users to attach specialized peripherals or transmit data to wireless devices

MIDI (Musical

Allow users to attach specialized peripherals or transmit data to wireless devices

MIDI (Musical Instrument Digital Interface) porteSATA portSCSI port IrDA (Infrared Data Association) portBl hBluetooth port

What is a bus?Channel that allows devices insideChannel that allows devices inside computer to communicate with each other

System bus connects processor and RAMBus width determines numberBus width determines number of bits transmitted at one timeWord size is the number of bits processor can interpret and execute at a given time

What is an expansion bus?All t i t ith i h lAllows processor to communicate with peripherals

PC Card USB PCIPCI AGPPC CardBus

USBBus

PCIBusExpressBus

AGPBus

What is a bay?O i i id tOpening inside system unit used to install additional equipmentadditional equipmentDrive bays typically hold disk driveshold disk drives

What is a power supply?What is a power supply?

Converts Fan keepsConvertsAC Power

into

Fan keepssystem unit components

DC Power cool

External peripherals might use an AC g

adapter, which is an external power supply

What is a mobile computer?N t b k i hi b tNotebook, weighing between 2.5 and 9 pounds, or mobile device such as a PDAdevice such as a PDA

What ports are on a notebook computer?What ports are on a notebook computer?

p. 214 Fig. 4-38 Next

What ports and slots are on a tablet PC?What ports and slots are on a tablet PC?

What are suggested processor and RAM configurations based on the needs of various typesconfigurations based on the needs of various types of users?

Over time, the system unit collects dust – even in a clean environmentclean environment

Preventative maintenance requires a few basic d tproducts: