Hardware: Input, Processing, and Output Devices

Chapter 3

Chapter Topics

• Computer system components

• The power, speed, and capacity of processing and main memory devices.

• Access methods, capacity and portability of secondary storage devices.

• Input & output devices

• The popular classes of computer systems

Hardware: Typical System

Printer (output) Monitor (output)

Speakers (output)

Mouse (input)

Keyboard (input)

System unit (processing and secondary storage)

Computer Hardware

CPU

Memory

System Unit

InputDevices

StorageDevices

OutputDevices

Peripherals

“Ports”“Motherboard”

“ExpansionSlots”

On the MotherboardA “motherboard”CPU

Expansion slots

A “firewire” card

Pins to attach toThe motherboard

A RAM chip

CPU

Fetch Decode

ExecuteWrite-back

Memory Registers

ALU

ControlUnit

CPUControl Unit •Maintains order

•Controls CPU activity

•Directs sequence of operations

Arithmetic/logic Unit

(ALU)

•Manipulates data

•Performs arithmetic computations

•Performs logical operations

Registers •Temporary storage areas for instructions or data

•offer the advantage of speed

•work under the direction of the control unit to accept, hold, and transfer instructions or data

Machine Cycle

Fetch Decode

Execute

Instruction Cycle

Execution Cycle

Write-back

Machine Cycle Time Measures

• Microseconds (1 millionth)

• Nanoseconds (1 billionth)

• Picoseconds (1 trillionth)

• MIPS (Millions of Instructions Processed per Second)

How fast is a Nanosecond?

• If one nanosecond is..• One mile

• One person

• One minute• One square mile

• Then one second is equivalent to …

• 2000 trips to the moon and back

• Population of China and the U.S.

• 1900 years• 17 times the land are

of the world

Data Bus

Fetch Decode

ExecuteWrite-back

“Word sizes”8 bits16 bits32 bits64 bits

Processing Characteristics

• Clock speed: electronic pulses affecting machine cycle time– Hertz: one cycle (pulse) per second– Megahertz (MHz): millions of cycles per

second

• Microcode: internal, predefined elementary operations in a CPU

Microcode Instruction Sets

• Complex instruction set computing: CPU contains many microcode instructions

• Reduced instruction set computing (RISC): Minimal set of microcode instructions

• Very Long Instruction Word (VLIW): Each microcode instruction is longer and does more.

Multiprocessing

• More than one CPU is present– Tasks are divided among CPUs in true “parallel

processing”

• Parallel processing uses multiple processors to execute instructions in concert.

Parallel Processing

Control CPU

Combined Results

Physical Characteristics of the CPU

• Digital circuits on chips

• Electrical current flows through silicon

• Moore’s Law states that transistor density of chips will double every 18 months

Memory Characteristics and Functions

MemoriesRandom AccessMemory (RAM)

CPU

PrimaryCache

SecondaryCache

System Bus

ExternalStorage Devices

Expansion slots

I/O Bus

ROM

ROM Chip and BIOS

•ROM stands for Read Only Memory•ROM is a non-volatile memory on a chip•The ROM chip contains

•Basic input/output system BIOS•The BIOS has the instructions necessary to start up your computer

RAM

•RAM stands for Random Access Memory•RAM is a volatile memory on a chip•RAM chips store information in “addresses” that can be accessed directly and quickly

Storage Media

• Storage devices retain data when power is switched off

• Storage devices are slower than memory devices like RAM

Memory Versus Storage

• Memory– A temporary holding place for data and instructions

– Consists of one or more chips on the motherboard

– Sometimes called primary storage

• Storage– The media on which data, instructions, and information are

kept, as well as the devices that record and retrieve these items

– Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage

– Storage is nonvolatile

Managing MemoryRemember the “Machine Cycle?”

Page is“swapped in”

Decoding andExecution

Page is“swapped out”

2. OS “kernel,” orsupervisor programbecomesmemory resident.

3. CPU reads andexecutes instructions

Starting Up

1. BIOS read from ROM

Storage Capacity

• The number of bytes (characters) a storage medium can hold

• Manufacturers use many terms to define the capacity of storage media

Storage Term Abbreviation Number

of bytes

Kilobyte

Megabyte

Gigabyte

Terabyte

Petabyte

KB

MB

TB

GB

PB

1 thousand

1 million

1 billion

1 trillion

1 quadrillion

Data Representation• A computer circuit represents the 0 or the 1

electronically by the presence or absence of an electronic charge.

• Binary Digit (Bit): Electronic State 1 On 0 Off• Binary system: two unique digits, 0 and 1• Bit: the smallest unit of data the computer can

represent• A byte: a group of 8 bits: represents a single

character in the computer

Bits and Bytes

•Byte• Eight bits

•Kilobyte - 1 thousand bytes•Megabyte - 1 million bytes•Gigabyte - 1 billion bytes•Terabyte - 1 trillion bytes

Coding Schemes• A byte provides enough different combinations of

0s and 1s to represent 256 individual characters. • A coding scheme: the defined combinations of 0s

and 1s that represent characters by patterns– ASCII(The American Standard Code for Information

Interchange)• ASCII represents 0-9, upper and lower case A-Z, and English

language punctuation in byte code

– EBCDIC (The Extended Binary Coded Decimal Interchange Code)

– Unicode

Data Storage Hierarchy

Bits

Character (byte)

Field

Record

01000100 01001111 01000111

D O G

DOG

DOG, FOUR LEGS, TWO EARS

FileDOG…..CAT….FOX….

Storage Modes

• Direct(Random) Access– records can be retrieved in any order– Faster (nanoseconds)– Usually more expensive

• Sequential– records must be retrieved in order– Slower (milliseconds)– Less expensive

The dog barked.

THEDOG..

Th

e

d og

bar

k ed

Sequential access versus Direct access

Sequential access– Method used for tape

– Reading and writing data consecutively

– You must forward or rewind the tape to a specific point to access a specific piece of data

– Much slower

– Utilized most often for long-term storage and backup

Direct access– Method used for floppy disks,

hard disks, and compact discs

– Also called random access

– You can locate a particular data item or file immediately, without having to move consecutively through items stored in front of the desired data item or file

– Faster

– Used as the primary method of storage

Storage Technologies• Magnetic

– Read/write head uses electrical impulses to create or interpret patterns of magnetic impulses

• Floppy disks• Hard disks• Tape

• Optical– Laser beam creates or reads non-reflective pits and

reflective land areas• CDs• DVDs

Ancient DecTapesystems

Disks

Sector

Cluster

Read/WriteHead

Access time

• The amount of time it takes the device to locate an item on a disk

• Defines the speed of a disk storage device

Memory (RAM)

Compact Disc

Floppy Disk

Tape

Hard Disk

cost

less

exp

ensi

ve

mor

e ex

pens

ive

speed

faster

slower

CD-R & CD-RW

CD-R (compact disc-recordable)

• You write on the CD-R using a CD recorder or a CD-R drive and special software

• The CD-R drive can read and write both audio CDs and standard CD-ROMs

• You cannot erase the disc’s contents

• Most CD-ROM drives can read a CD-R

CD-RW (compact disc-rewritable)

• An erasable disc you can write on multiple times

• You must have CD-RW software and a CD-RW drive

DVD-ROM (digital video disc-ROM)

• An extremely high capacity compact disc capable of storing from 4.7 GB to 17 GB

• You must have a DVD-ROM drive or DVD player to read a DVD-ROM

• Looks just like a CD-ROM but data, instructions, and information is stored in a slightly different manner to achieve a higher storage capacity

Magnetic Tapes

• A magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost

• A tape drive reads from and writes data and information on a tape

• Older computers used reel-to-reel tape drives• A tape cartridge is a small, rectangular, plastic housing for

tape used in today’s tape drives• Used by business and home users to backup personal

computer hard disks• Both external and internal tape units for personal computers• Larger computers use tape cartridges mounted in a separate

cabinet called a tape library

Storage techniques used in an enterprise system

• Storage area network (SAN): A high-speed network that connects storage devices

• Tape library: A high-capacity tape system that works with multiple tape cartridges for storing backups of data, information, and instructions

• RAID system: Ensures that data is not lost if one drive fails

• Server: Stores data, information, and instructions need by users on the network

• CD-ROM jukebox: Holds hundreds of CD-ROMs that can contain application programs and data. Also called a CD-ROM server

• Internet backup: Stores data, information, and instructions on the Web

RAID

• Redundant array of independent disks• A type of hard disk system that connects several

smaller disks into a single unit that acts like a single large hard disk

• More reliable than a traditional disk system but quite expensive

• RAID duplicates data, instructions, and information to improve data reliability

How does RAID work?

Mirroring(RAID Level 1)

Striping

Level 1, called mirroring, has one backup disk for each disk

Levels beyond level 1 use a technique called striping, which splits data, instructions, and information across multiple disks in the array

Additional Devices and Media

• Memory Cards– A thin, credit card-sized device– Fits into a PC Card slot on a notebook other personal computer– Different types and sizes add storage, additional memory,

communications, and sound capabilities to a computer– Three types of PC Card– Advantage of a PC Card for storage is portability between systems

• Flash memory– Also called flash ROM or flash RAM– Nonvolatile memory that can be erased electronically and

reprogrammed– Stores data and programs on many handheld computers and devices– Flash memory cards store flash memory on removable devices instead

of chips

Input and Output

Interrupts

Device Driversoftware

Input devices

• What is input?– Any data or instructions you enter into the memory of

the computer

– Users can input data and instructions in a variety of ways

• Types of input– Data: A collection of raw unprocessed facts, figures,

and symbols

– Instructions: Programs, Commands, User responses

Data

• Data can be human or machine readable• Data entry converts human readable data into

machine-readable form• Data input transfers machine-readable data into

the system• Source data automation

Input Devices

• Personal computer input devices– Keyboard– Mouse

• Voice-recognition devices

• Digital cameras

• Terminals

Input Devices

• Scanning devices• Optical data readers• Bar code scanners• MICR devices• POS (point-of-sale) devices• Pen input devices• Light pens• Touch screens

Output Devices

• Monitors– Cathode Ray Tubes (CRTs)– Liquid Crystal Displays (LCDs)

• Active matrix• Passive matrix

• Printers• Plotters• Computer Output Microform (COM)• Music Devices

• Contains a cathode ray tube (CRT), a large sealed, glass screen

• The screen is coated with tiny dots of phosphor material

• A pixel, or picture element, is a single point in an electronic image

• Three dots (red, blue, and green) combine to make up each pixel

What is a CRT monitor?

CRT monitor screen

cathode ray tube

What is a liquid crystal display (LCD) monitor?

• A type of flat-panel display• Uses liquid crystals between two sheets of

material to present information on a screen• An electric current passes through the

crystals which creates the images on the screen

800 x 600typically the

standard

What is display resolution?

• Describes the sharpness and clearness of an image• Resolution of a display device stated as dots, or pixels

1280 x 1024maximum resolution

of most monitors

800 horizontal

pixels

600 vertical pixels

Total of 480,000 pixels on screen2048 x 1536

maximum for high-end monitors

What is a video card?• Converts digital output

from the computer into an analog video signal

• Sends the signal through a cable to the monitor

• Controls how the display device produces the picture

• Also called a graphics card or video adapter

How does video travel from the processor to a CRT monitor?

Step 1: The processor sends digital video data to the video card.

Step 2: The video card’s digital-to-analog converter (DAC) converts the digital video data to an analog signal.

Step 3: The analog signal is sent through a cable to the CRT monitor.

Step 4: The CRT monitor separates the analog signal into red, green, and blue signals.

Step 5: Electron guns fire the three color signals to the front of the CRT.

Step 6: An image displays on the screen when the electrons hit phosphor dots on the back of the screen.

24-bit video card

Uses 24 bits to store information about each pixel

Can display 16.7 million colors

224 = 16.7 million

colors

What is bit depth?• The number of bits a video

card uses to store information about each pixel

• Also called the color depth• Determines the number of

colors a video card can display

• The greater the number of bits, the better the resulting image

8-bit video card (8-bit color)

Uses 8 bits to store information about

each pixel

Can display 256 different colors

28 =2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 =

256 colors

What are various video standards?

• The Video Electronics Standards Association (VESA) develops video standards

Computer System Types

• Network computer

• Personal computer

• Workstation

• Midrange computer

• Mainframe computer

• Supercomputer

Selecting and Upgrading Computer Systems

• Computer system architecture: the configuration of a computer system’s hardware components