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(1)

Computer Hardware

Components:

(2)

Computer Hardware

Components



In this chapter:

◦

How did the computer become known as

the stored-program computer?

 _{Do they all have the same characteristics?}

◦

Memory on chips and memory on

magnetic media, how do they differ?

◦

What do you look for when comparing

memory devices?

◦

How is information moved around within

the computer?

◦

How can you help your computer run

(3)

Basic Concepts of

Computer Hardware

 This model of the typical digital computer is often called the von Neumann computer.

◦ Programs and data are stored in the same memory:

primary memory.

◦ The computer can only perform one instruction at a time.

CPU

(Central Processing Unit) Input

Units

(4)

Basic Concepts of Computer

Hardware



Input/Output (I/O): Refers to the

process of getting information

into and out of the computer.

◦

Input: Those parts of the computer

receiving information to programs.

(5)

Sources of Data for the

Computer



Two types of data stored within a

computer:

◦

Original data

or

information

: Data being

introduced to a computing system for the first

time.

 _{Computers can deal directly with printed text,}

pictures, sound, and other common types of information.

◦

Previously stored data

or

information

:

Data that has already been processed by a

computer and is being stored for later use.

 _{These are forms of binary data useful only to the}

computer.

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Input Devices



Two categories of input

hardware:

◦

Those that deal with original data.

◦

Those that handle previously stored

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Input Devices



Input hardware: Those that deal with

original data.

◦

Keyboard

◦

Mouse

◦

Voice recognition hardware

◦

Scanner

◦

Digital camera



Digitizing: The process of taking a

visual image, or audio recording and

converting it to a binary form for the

computer.

(8)

Input Devices



Connecting Hardware to the computer:

◦

Hardware needs access through some

general input/output connection.

 _Port_{: The pathway for data to go into and out of}

the computer from external devices such as keyboards.

 _{There are many standard ports as well as custom}

electronic ports designed for special purposes.

 _{Ports follow standards that define their use.}

 _{SCSI, USB: Multiple peripheral devices (chain).}  _{RS-232, IDE: Individual peripheral devices.}

 _{Peripheral device}_{: A piece of hardware like a}

(9)

Input Devices



Connecting Hardware to the

computer: (continued)

◦

Hardware needs software on the

computer that can service the

device.



_{Device driver}

_{: Software addition to the}

operating system that will allow the

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Input Devices



Common Basic Technologies for

Storing Binary Information:

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Input Devices



Electronic Circuits

◦

Most expensive of the three forms for

storing binary information.

◦

A flip-flop circuit has either one

electronic status or the other. It is said

to flip-flop from one to the other.

◦

Electronic circuits come in two forms:



_Permanent

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Input Devices



Magnetic Technology

◦

Two parts to most of the magnetic

forms of information storage:



_The

_medium

_{that stores the magnetic}

information.

 _{Example: Floppy disk. Tiny spots on the disk} are magnetized to represent 0s and 1s.



_The

_device

_{that can “read” that}

information from the medium.

 _{The drive spins the disk.}

 _{It has a magnetic sensing arm that moves} over the disk.

(13)

Input Devices



Optical

◦

Uses lasers to “read” the binary

information from the medium,

usually a disc.



_{Millions of tiny holes are “burned” into}

the surface of the disc.

(14)

Input Devices



Secondary Memory Input Devices

◦

These input devices are used by a

computer to store information and then

to retrieve that information as needed.



_{External to the computer.}



_{Commonly consists of floppy disks, hard}

disk drives, or CD-ROMs.

◦

Secondary memory uses binary.



_{The usual measurement is the byte.}

 _{A byte consists of 8 binary digits (bits). The byte is}

(15)

Input Devices



The four most important

characteristics of storage

devices:

◦

Speed and access time

◦

Cost / Removable versus

non-removable

◦

Capacity

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Input Devices



Speed

(Access time) - How fast

information can be taken from or

stored onto the computer

memory device’s medium.

◦

Electronic circuits: Fastest to access.



_{40 billionths of a second.}

◦

Floppy disks: Very slow in

comparison.

(17)

Input Devices



Capacity

- The amount of

information that can be stored on

the medium.

Unit Description

1 bit 1 binary digit

1 nibble 4 bits

1 byte 8 bits

1 kilobyte 1,024 bytes

1 megabyte 1,048,576 bytes

1 million bytes

1 gigabyte 1,073,741,824 bytes

1 billion bytes

(18)

Input Devices



Type of Access



_Sequential

_{- Obtained by proceeding}

through the storage medium from the

beginning until the designated area is

reached (as in magnetic tape).

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Primary Memory

 Primary storage or memory: Is where the data and

program that are currently in operation or being accessed are stored during use.

◦

Consists of electronic circuits:

Extremely fast and expensive.

◦

Two types:



_RAM

_{(non-permanent)}

 _{Programs and data can be stored here for the}

computer’s use.

 Volatile: All information will be lost once the computer shuts down.



_ROM

_(permanent)

(20)

The Central Processing

Unit



The Central Processing Unit ( CPU)

◦

Often referred to as the “brain” of the

computer.

◦

Responsible for controlling all activities of

the computer system.

◦

The three major components of the CPU are:

1. Arithmetic Unit (Computations performed)

Accumulator (Results of computations kept here)

2. Control Unit (Has two locations where numbers are kept) Instruction Register (Instruction placed here for analysis) Program Counter (Which instruction will be performed next?) 3. Instruction Decoding Unit (Decodes the instruction)

(21)

Output Devices



Output units store and display

information (calculated results and

other messages) for us to see and use.

◦

Floppy disk drives and Hard disk drives.

◦

Display monitors: Hi-resolution monitors

come in two types:

 _{Cathode ray tube}_{(CRT) - Streams of electrons}

make phosphors glow on a large vacuum tube.

 _{Liquid crystal display}_{(LCD) - A flat panel}

display that uses crystals to let varying amounts of different colored light to pass through it.

(22)

Output Devices



Audio Output Devices

◦

Windows machines need special audio

card for audio output.

◦

Macintosh has audio playback built in.

◦

Audio output is useful for:

 _Music

 _{CD player is a computer.}

 _{Most personal computers have CD players that can}

access both music CDs and CD-ROMs.

 _{Voice synthesis (becoming more human}

sounding.)

 _Multimedia

 _{Specialized tasks (i.e.: elevator’s floor}

(23)

Output Devices



Optical Disks: CD-ROM and DVD

◦

CD-ROM (Compact Disk - Read Only

Memory)

 _{By its definition, CD-ROM is Read Only.}

 _{Special CD drives “burn” information into blank}

CDs.

 _{Burn: A laser is used to “burn” craters into the surface to}

represent a binary 1.

 _{Two main types of CDs:}

 _{CD-R (Compact Disk - Recordable)}  _{CD-WR (Compact Disk - ReWritable)}

(24)

Output Devices



DVD (Digital Versatile Disk)

◦

Allows up to 17 gigabytes of storage

(from 4.7 GB to 17 GB).

◦

Compatible with older CD-ROM

technology.

(25)

Output Devices



Storage Requirements: How much

storage capacity is needed for…

◦ One keystroke on a keyboard. 1 byte (8

bits)

◦ One page single-spaced document. 4.0 K

◦ Nineteen pages formatted text. 75 K

◦ One second of high-fidelity sound. 95-110 K

◦ Complete word processing program. 8.4 MG



Storage Capacity: How much data

can be stored on…

◦ One inch of 1/2 in. wide magnetic tape. 4 K

◦ One 3 1/2” floppy disk, high density. 1.4 MG

◦ One Compact Disk. 650 MG

(26)

Moving Information

Within the Computer



How do binary numerals move

into, out of, and within the

computer?

◦

Information is moved about in bytes,

or multiple bytes called words.



_Words

_{are the fundamental units of}

information.



_{The number of bits per word may vary per}

computer.



_{A word length for most large IBM}

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Moving Information

Within the Computer

 Bits that compose a word

are passed in parallel from place to place.

◦ Ribbon cables:

 _{Consist of several wires,}

molded together.

 One wire for each bit of the word or byte.

 Additional wires

coordinate the activity of moving information.

 _{Each wire sends}

(28)

Moving Information

Within the Computer

 Example of

sending the word WOW over the ribbon cable

◦

Voltage

pulses

correspondi

ng to the

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Packaging the Computer



The many physical

forms of the general

purpose computer:

◦ All follow general organization:

 _{Primary memory}  _{Input units}

 _{Output units}

 _{Central Processing Unit}

◦ Grouped according to speed, cost, size, and complexity. Super Computers Mainframe Computers Minicomputers Microcomputer Palmtop Computer Calculator

Fast Expensive Complex Large

(30)

Software Tools for

Maintaining Your Computer

Hardware

 Utility Programs exist that can help diagnose and solve computer hardware problems.

◦

Four major problem areas where

utility programs are helpful:



_{Finding and fixing problems.}

 Testing Input/Output peripherals.

 _{Testing RAM, motherboard, video cards.}

 Recovering deleted files or fixing damaged disks.



_{Improving computer performance.}

 _{De-fragmenting a disk (Packs all files closer together).}



_{Preventative maintenance.}



_{Troubleshooting.}

(31)

Computer

Peripherals

and Data Storage

(32)

Printers



Four main types:

◦

Dot matrix

◦

Laser

◦

Ink jet

(33)

Impact vs. Non-Impact



Impact printers physically transfer

a dot or shape to the paper



Of those in the preceding slide,

only dot-matrix uses impact

printing



Non-impact printers spray or lay

down the image with impact



Impact printers remain important

(34)

Printers



Four main types:

◦

Dot matrix

◦

Laser

◦

Ink jet

(35)

How it works

A print-head moves back-and-forth in front of

forms (paper) on which characters or graphic

images are transferred. The print-head contains

numerous wires, typically from 9 to 24. Each

wire is part of a solenoid-like unit. A pulse

(36)

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Dot Matrix Print Head

Front view

Side view

Print wires

(e.g., 12)

(38)

Dot Matrix Impact Printing

Print wire

Ribbon

Paper

Platen

(39)

Specifications



cps

◦

characters per second

◦

Varies by quality of print (e.g., draft vs. final)



lpm

◦

lines per minute (related to cps)



Forms

◦

Maximum number of layers of paper that can

by printed simultaneously

◦

Specified as

n

-part forms (e.g., 4-part forms)



mtbf

(40)

Noise



Dot matrix printers are

notoriously noisy!



This is a major disadvantage in

(41)

Uses



Primarily two:

◦

Any situation that requires multi-part

forms

◦

Small printers, such as



_Calculators



_{Adding machines}

(42)

Dot Matrix Printer

Example - 1

Specifications • 800 cps • 400 lpm

(43)

Dot Matrix Printer

Example - 2

Specifications

• Printhead wires: 9

• Printhead life: 200 million characters • Print speed:

• near letter quality: 105 cps • utility: 420 cps

• high speed draft: 550 cps • Number of copies: 8

(44)

Printers



Four main types:

◦

Dot matrix

◦

Laser

◦

Ink jet

(45)

Operation of a Laser

Printer

 Four steps

1. A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be

fanned out across the drum. The drum rotates to the next line, usually 1000th or 1600th of an inch.

The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged

wherever a dot is to be printed.

Laser

Spinning mirror Photosensitive

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Operation of a Laser

Printer

2. As the drum continues to rotate, the charged part of the drum passes through a tank of black powder

called toner. Toner sticks to the drum wherever the charge is present. Thus, the pattern of toner on the drum matches the image.

(47)

Operation of a Laser

Printer

3. A sheet of paper is fed toward the drum. A charge wire coats the paper with electrical charges. When the paper contacts the drum, it picks up the toner from the drum

(48)

Operation of a Laser

Printer

4. As the paper rolls from the drum, it passes over a heat and pressure area known as the fusing system. The fusing system melts the toner to the paper. The printed page then exits the printer.

As the same time, the surface of the drum passes over another wire, called a corona wire. This wire resets the charge on the drum, to ready it for the next page.

Corona wire

(49)

Specifications



ppm

◦

Pages per minute

◦

Typically 4-10 ppm



dpi

◦

Dots per inch

(50)

Laser Printer Example

Laserjet 5000 Series from Hewlett Packard Co.

(51)

Printers



Four main types:

◦

Dot matrix

◦

Laser

◦

Ink jet

(52)

Background



Inkjet technology was developed

in the 1960s



First commercialized by IBM in

1976 with the 6640 printer



Cannon and Hewlett Packard

developed similar technology

(53)

How it works

Characters and graphics are 'painted‘ line by line to from a pattern of dots as a print head scans horizontally across the paper. An ink-filled print cartridge is attached to the inkjet's print head. The print head contains 50 or more ink-filled chambers, each attached to a nozzle. An electrical pulse flows through thin resistors at the bottom of each chamber. When current flows through a resistor, the resistor heats a thin layer of ink at the bottom of the chamber to more than 900 degrees Fahrenheit for several millionths of a second . The ink boils and forms a bubble of vapour. As the vapour bubble expands, it pushes ink through the nozzle to form a droplet at the tip of the nozzle. The droplet sprays onto the paper.

The volume of the ejected ink is about one millionth that of a drop of water from an eye-dropper. A typical character is formed by an array of these drops 20 across and 20 high. As the resistor cools, the bubble

(54)

(55)

Printers



Four main types:

◦

Dot matrix

◦

Laser

◦

Ink jet

(56)

How it works

Thermal dye transfer printers, also called dye sublimation printers, heat ribbons containing dye and then diffuse the dyes onto specially

coated paper or transparencies. These printers are the most expensive and slowest, but they produce continuous-tone images that mimic actual

photographs. Note that you need special paper, which is quite expensive. A new breed of thermal dye transfer printers, called snapshot printers, produce small photographic snapshots and are much less expensive than their full-size cousins.

(57)

Dithering

Dithering is creating the illusion of new colours and shades by varying the pattern of dots. Newspaper photographs, for example, are dithered. If you look closely, you can see that different shades of grey are produced by varying the patterns of black and white dots. There are no grey dots at all. The more dither patterns that a device or program supports, the more

shades of grey it can represent. In printing, dithering is usually called halftoning, and shades of grey are called halftones.

Note that dithering differs from grey scaling. In grey scaling, each individual dot can have a different shade of grey.

(58)

Plan



Printers



Scanners



Keyboards

(59)

How it works

A scanner works by digitizing an image. A scanning mechanism consists of a light source and a row of light sensors. As light is reflected from individual points on the page, it is received by the light sensors and