Chapter 2:

Computer Hardware

2.1 Central Processing Unit

2.2 Primary memory devices

2.3 Secondary memory device

2.4 Input Devices

2.5 Output Devices

Session 2014-15 B.Ed Elementary

Central Processing Unit• The part of the computer performs the bulk of data

processing operations is called the central processing unit

• The CPU is made up of three major parts:– Register set

– ALU

– Control unit

The central processing unit (CPU) of a computer is the main unit that dictates the rest of the computer organization

• 1. Register set: Stores intermediate data during the execution of instructions;

• 2. Arithmetic logic unit (ALU): Performs the required micro-operations for executing the instructions;

• 3. Control unit: supervises the transfer of information among the registers and instructs the ALU as to which operation to perform by generating control signals.

ControlUnit

Registers

ArithmeticLogic Unit

• Central Processing Unit = “brain”

• Executes programs by:

– Fetching and decoding the next instruction from memory

– Execute it

• Consists of:

– Control Unit

– Arithmetic Logic Unit (ALU)

– Registers (high-speed memory)

• Program Counter (PC)

• Instruction Register (IR)

Disk PrinterMain

Memory

ControlUnit

Registers

ArithmeticLogic Unit

Bus

I/O Devices

• 1 Bit- Binary digit ‘0’ or ‘1’.

• 1 Nibble = 4 Bits

• 1 Byte = 8 Bits

• 1 Kilo Byte (KB) = 1024 Bytes = 210 Bytes

• 1 Mega Byte (MB) = 1024 KB = 220 Bytes

• 1 Giga Byte (GB) = 1024 MB = 230 Bytes

• 1 Tera Byte (TB) = 1024 GB = 240 Bytes

• 1 Peta Byte (PB) = 1024 TB = 250 Bytes

• 1 Exa Byte (EB) = 1024 PB = 260 Bytes

• Also known as the main memory.

• It is mostly temporary or working storage.

• Data access speed is faster as compared to

Secondary memory devices.

• Four principal types of memory chips are:

– RAM, ROM, CMOS, and Flash

• Holds temporarily (hence volatile):

– Software instructions.

– Data before and after it is processed by the

CPU.

• Volatile means the contents are lost when

the power goes off or is turned off.

• DRAM (Dynamic RAM) must be constantly

refreshed by the CPU.

• SDRAM (Synchronous DRAM)

synchronized by the system clock.

• SRAM (Static RAM) no refreshing.

• DDR-SDRAM (Double-data rate SDRAM)

• ROM chips contain fixed start-up

instructions, mostly loaded by the

manufacturer.

• It holds instructions that run the computer

when it is first turned on (BIOS).

• It is permanent memory (Non-volatile)

• PROM (Programable ROM)

• EPROM (Eraseable PROM)

– UVEPROM

– EEPROM also known as flash memory

• Complementary Metal Oxide

Semiconductor are powered by a battery

and thus they do not lose their contents

when the power is turned off.

• Can be reprogrammed.

• Does not require a battery.

• Can be erased and reprogrammed more than

once.

• Used in PCs, pagers, cell phones, MP3 players

etc.

• Flash memory is also used in newer PC’s for

BIOS instructions; they can be updated

electronically.

• Pronounced as ‘Cash’.

• Cache temporarily stores instructions and data

that the processor is likely to use frequently. Thus,

cache speeds up processing.

• SRAM chips are commonly used as cache.

• Three kinds of Cache:

– L1 part of the processor. Less capacity, operates faster.

– L2 not part of the processor, high capacity.

– L3 on the mother board- on very high-end computers.

• .

Central Processing Unit

Output

Devices

Cache

Memory

Primary

Storage

SecondaryStorageDevices

ControlUnit

ALU

Special

Purpose

Processors

Output

Devices

Input

Devices

• Storage device stores information to be recalled and used at a later time

• Storage device consists of:

•Storage medium

•Storage device

• Three major technology types for information storage:

•Magnetic

•Optical or laser

•Flash memory

• Storage devices hold data, even when the computer is turned

off.

• The physical material that actually holds data is called a

storage medium. The surface of a floppy disk is a storage

medium.

• The hardware that writes data to or reads data from a storage

medium is called a storage device. A floppy disk drive is a

storage device.

• The two primary storage technologies are magnetic and

optical.

• Diskettes (floppy disks) (FDD)

• Hard disks (HD)

• High-capacity floppy disks (ZIP Disk)

• USB flash drive

• Magnetic tape

• Compact Disk Read-Only Memory (CD-

ROM)

• Digital Video Disk Read-Only Memory

(DVD-ROM)

• CD-Recordable (CD-R)

• CD-Rewritable (CD-RW)

• Purpose:

– Long-term, nonvolatile storage

– Large, inexpensive, slow level in the storage hierarchy

• Disk composition

– A magnetic disk consist of a collection of platters (1to 20 per

disk) that rotate on a spindle.

– Disk surface divided into tracks (1000 to 4800 per platter).

– Tracks are divided into sectors (64 per track), which are the

smallest unit that can be read or written.

• Up to 15,000 rpm

• A read/write head travels across a spinning

magnetic disk, retrieving or recording data

• An optical disk is a high-capacity storage medium. An

optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny

dents (pits) and flat spots (lands), which cause light to be

reflected differently.

• When an optical drive shines light into a pit, the light

cannot be reflected back. This represents a bit value of 0

(off). A land reflects light back to its source, representing a

bit value of 1 (on).

• CD-ROM: compact disc ROM (Read Only Memory)

– Capacity: 650MB

• CD-R: compact disc recordable

• CD-RW: compact disc rewritable

• DVD: digital versatile disc

– Capacity: 4.7GB – 17GB

• DVD-R

• DVD-RW

• An optical disk is a high-capacity storage medium. An

optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny

dents (pits) and flat spots (lands), which cause light to be

reflected differently.

• When an optical drive shines light into a pit, the light

cannot be reflected back. This represents a bit value of 0

(off). A land reflects light back to its source, representing a

bit value of 1 (on).

• An optical disk is a high-capacity storage medium. An

optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny

dents (pits) and flat spots (lands), which cause light to be

reflected differently.

• When an optical drive shines light into a pit, the light

cannot be reflected back. This represents a bit value of 0

(off). A land reflects light back to its source, representing a

bit value of 1 (on).

• Input device captures information and translates it into a form that can be processed and used by other parts of your computer. •Keyboards

•Pointing devices

•Game controllers

•Scanners

•Styluses

•Microphones

•Digital cameras

•Web cams

• The keyboard is the most common input device. Types of keyboards include:

• Wireless

• Multimedia and one-touch access

• Portable keyboards for PDAs

Types of Input Devices

• Pointing devices are mainly used to choose and enter commands

• Pointing devices tend to have PS/2 connectors or USB connectors

• PS/2 connector fits into a PS/2 port, which a small round socket with small holes that fit the pins on the connector

• USB connectors fit into USB ports, and these are small rectangular openings on the back or front of your computer, or even on your keyboard or monitor

• Various pointing devices are available

• Types of pointing devices:

• Mouse

•Mechanical mouse

•Optical mouse

•Wireless mouse

• Trackball

• Touchpad

• Pointing stick

• Game controllers are used mainly to play games

• Types of gaming devices

• Gamepads

• Joysticks

• Gaming wheels

• Force feed

• Other types of input devices include:

• Scanners

• Styluses

• Microphones

• Digital cameras

• Web cams

•Scanner is a light sensitive device that helps you

copy or capture images, photos, and artwork

that exist on paper. Types of scanners include:

•Flatbed

• Stylus is an input device consisting of a thin

stick that uses pressure to enter information

or to click and point

• Styluses are used with:

•PDAs

•Tablet PCs

•Graphics tablets

• Microphones are used to input audio

• Three main types of microphones are:•Desktop microphones

•Headsets

•Directional microphones

• Speech recognition is increasingly being included in application software

Digital Cameras• Digital cameras are used to: • Download images to a computer

• Post pictures to the Web

• Produce videos

• Resolution is measured in megapixels

• Higher the resolution, better the image quality, but the more expensive the camera

• Web cam is a video camera

that can be used to take images

for uploading to the Web

• Output devices take information within your computer and present it to you in a form that you can understand

• Main output devices:

– Monitors

– Printers

– Speakers

• Devices with flat-panel displays

• Tablet PCs

• PDAs

• Cellular phones

• Desktop computers

• CRTs

• Flat-panel displays

– Gas plasma

– LCD (liquid crystal display)• Passive matrix

• Active matrix– Called TFT (thin film transistor)

– Separate transistor for every pixel

• Screen size measured as a diagonal line across the screen – from corner to opposite corner

• Resolution the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)

• Pixels (or picture element) dots that make up the image on your screen

• Dot pitch is the distance between the centers of a pair of like-colored pixels

• Refresh rate the speed with which a monitor redraws the image of the screen, and is measured in hertz

©2003 The McGraw-Hill Companies

• Inkjet – most popular

– Makes images by forcing droplets

through nozzles

– Top speed is 20 pages per minute

• Laser

– Forms images using an

electrostatic process

– Prints between 3 and 30 pages per

minute

• Resolution of a printer is the

number of dots per inch (dpi) it

produces.

• Higher the resolution, better the

image, and usually the more

costly the printer

Printers - Cont. • Multifunction printer:

• Scan, copy, fax, and print

• Can be either inkjet or laser

• Cost less than buying

individual units

• Take up less desk space

• A speaker is a device that produces computer output as sound

• Speakers are common devices in computer systems Examples include:

• Built-in speaker

• Two-device set speakers

• Surround sound speakers

• Data Projector

Projects the image onto a wall screen.