computer fundamentals hardware

8/8/2019 Computer Fundamentals Hardware

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Computer Fundamentals

Hardware

SoftwareNetworking


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What are Computers and Networks?

Definitions

(Collins English Dictionary): 'A device, usually electronic, thatprocesses data according to a set of instructions'

(Ques Computer Users Dictionary): 'A machine capable offollowing instructions to alter data in a desirable way and to

perform at least some of these operations without human

intervention'.

(Microsoft Press Computer Dictionary, 3rd Ed.: 'Any machinethat does three things: accepts structured input, processes itaccording to prescribed rules, and produces the results as output'.

Basically, a computer is: An electronic device Operates under the control of instruction stored in its own

memory unit

Can accept data (input) Processes data arithmetically and logically Produces results (output) Can store the results for future use


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Types of Computer Systems

Computers can be "classified" on the basis of:

1. Type of data2. Use3. Size and complexity4. Function


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(Based on the type of data)

1. Digital Computers - store data in discrete units and performarithmetical and logical operations at very high speed

2. Analog Computers - have no memory and are slower; havecontinuous rather than discrete input; widely used in laboratoryequipment to monitor ongoing, continuous changes andrecord/graph these.


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(Based on their use)

1. General Purposeo Perform a wide variety of processing tasks

o These are the most common

2. Dedicated or Special Purpose

o Fundamentally the same as a general purpose

o Programmed for a specific purpose

o Advent of cheap microprocessors has lead to massivegrowth in usage/market penetration

o Used in a variety of consumer products, microwaves,telephones, washing machines, etc.


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(Based on size and complexity)

1. Mainframes2. Minicomputers

3. Microcomputers

4. Personal Digital Assistants

These categories are almostout-of-date because of thewide scale introduction ofcomputer networks andpowerful PCs.


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Mainframes

A multi-user computer designed to meet the computing needs of alarge organization

Originally the term referred to the metal cabinet housing the CPU

Generally refers to computers of the 1950s and 1960s

Large number of dumb terminals were used for input/output andit had a large number of peripherals attached

Can process a number of applications concurrently. This is known

as multi-processing which aims to keep the CPU as busy aspossible

Usually housed in special rooms.


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Minicomputers

Scaled down mainframe Designed to meet the computing needs of a department or small

company. Typically 4-100 concurrent users.

Usually run without a special environment

Can support a number of concurrent applications and often uses atime-sharing operation system that aims to keep the users busy.


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Microcomputer

Based on a single silicon chip (IC or microprocessor) Appeared mid-to-late 70s. (E.g. Apple II, TRS-80, Sinclair

Spectrum, Commodore PET, etc.)

'Multi-media' systems now available

o Enable the integration of sound, video, graphics, as well astext into software

o At present the incorporation of a sound card, speakers,

microphone, and CD-ROM drive defines a multi-media PC Portable versions now available.

o Basically, the same except for the Video Display Unit.

o Peripherals connected via PCMCIA/PC Card are nowpopular

Notes:

Since mid 80s the distinction between micro and mini has becomeblurred

Now microcomputers (PCs and Workstations) are more powerfulthan older mainframes (see below)


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Personal Digital Assistants

PDAs are portable computers taken further Pocket sized designed for use on the move

Use a pen as input (write directly to screen)

Software 'attempts' to translate handwriting by reference tostored prototypes


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(Based on function)

1. Centralized Computing systems - Services several userssimultaneously

2. Stand-alone Computers - Have no sharing of resources, e.g. a self-contained PC

3. Distributed Computing Systems

1. Each user has access to the computing power of the

machine they are on, however certain resources andperipherals are shared (e.g. file store and printing)

2. Users can usually obtain further computing facilities andpower by connecting to other computers (nodes) on thenetwork


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What is a Network?

A network is often referred to as a Local Area Network [LAN].

Can be defined as a computer based communication and dataexchange system;

Is created by the physical connection between two or morecomputers;

Is capable of supporting computers providing special services.

1. A File Server

Provides access to files for (all) workstations on the LAN

Usually is a single, powerful machine with fast huge harddisk(s)

Requires a type of Network Filing System (NFS) to operate.This enables the disks on the file server to appear as thoughthey are local disks on users workstation. (Often referred toas mounted disks)

2. A Print Server

A computer dedicated to receiving and temporarily storing

files to be printed. The print server runs special printspooler software that establishes printer queues and enablesbackground printing. This enables the print server toperform other tasks as well as print serving.

3. A Computer Server

A computer dedicated to performing complex calculation.

4. Other Servers

A HTTP server provides WWW pages

A FTP server provides files via File Transfer Protocol (anasynchronous communication method. Used extensively fortransfer of programs)


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Data Representation


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Data is either in Digital or Analog form.

Most Computers work with Digital Data

Computers store all data as a series of ones and zeros.

Computers Use the Binary System to representnumbers and other characters.


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Binary Numbers

Binary digits are used to represent information in computers using

magnetic or electrical devices.

Terminology:

A Bit is short for Binary Digit.

Bits can either have the value of 1 or 0, which corresponds to trueand false (or ON and OFF).

8 bits make a byte.

1024 bytes make up a kilobyte (Kb).

1024 kilobytes make up a megabyte (Mb).

All machines have a wordsize

o Wordsize is a fundamental unit of storage, for example 8-bits, 16-bits 32-bits, etc.

The size of a word (in bytes) differs between machines. A Pentiumbased machine is 32-bit.

(2n -1)

wheren = # of bits


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Decimal Number System(base10)

This is the numbering system that we have grown up with.

To understand the other numbering systems (binary, octal,hexadecimal) we will start by recalling the 'rules' associated with thedecimal (or base10) system.

With the decimal numbering system, we use a base of 10.

This means that we go up in increments of 10:

1101001000etc..

Example

Consider the following decimal number:

136.25.

What does this actually mean?

This number means:102 * 1 = 100.0101 * 3 = 30.0

10

0

* 6 = 6.010-1 * 2 = 0.210-2 * 5 = 0.05

total = 136.25


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Binary Number System(base2)

With the binary numbering system, we use a base of 2 instead of a base

of 10.

This means that we go up in increments of 2:

124816

3264128256512etc..

Example:Consider the binary number

1101.01.

Again in its full form this means:

23 * 1 = 1000.0 (8 in decimal)22 * 1 = 100.0 (4 in decimal)21 * 0 = 00.0 (0 in decimal)20 * 1 = 1.0 (1 in decimal)

2

-1

* 0 = 0.0 (0.0 in decimal)2-2 * 1 = 0.01 (0.25 in decimal)

total = 1101.01 (13.25 in decimal)


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The following shows the first integers and their binary equivalents (andhow they are derived):

decimal binary

0 0000 (0 * 2

3

+ 0 * 2

2

+ 0 * 2

1

+ 0 * 2

0

)1 0001 (0 * 23 + 0 * 22 + 0 * 21 + 1 * 20)2 0010 (0 * 23 + 0 * 22 + 1 * 21 + 0 * 20)3 0011 (0 * 23 + 0 * 22 + 1 * 21 + 1 * 20)4 0100 (0 * 23 + 1 * 22 + 0 * 21 + 0 * 20)5 0101 (0 * 23 + 1 * 22 + 0 * 21 + 1 * 20)6 0110 (0 * 23 + 1 * 22 + 1 * 21 + 0 * 20)7 0111 (0 * 23 + 1 * 22 + 1 * 21 + 1 * 20)8 1000 (1 * 23 + 0 * 22 + 0 * 21 + 0 * 20)9 1001 (1 * 23 + 0 * 22 + 0 * 21 + 1 * 20)


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Octal Number System(base8)

With the octal numbering system, we use a base of 8 instead of a base of

10 or 2.

As it turns out, each octal "digit" will represent a group of 3 bits orbinary digits.


110101010

This 9 bit binary number can be grouped into 3 groups of 3 bits:

110 101 010

6 5 2

This gives us the octal number:

6528

This octal number (and associated binary number) is a representationof the following decimal number:

42610


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Hexadecimal Number System(base16 or baseH)

Although it is very convenient for computers to use 0 and 1 it is difficult

for humans to readily identify binary numbers.

Hexadecimal (Hex) acts as an interim number system between binaryand ourselves as it is more recognizable yet easy to convert to and frombinary.

With the hexadecimal numbering system, we use a base of 16 instead ofa base of 10, 8, or 2.

As it turns out, each hexadecimal "digit" will represent a group of 4 bitsor binary digits (1 byte can be expressed by two hexadecimal digits).

The Hexadecimal system uses the following "digits"

Hexadecimal Digit Decimal Digit1 12 23 34 4

5 56 67 78 89 9A 10B 11C 12D 13

E 14F 15


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100101110100

This 12 bit binary number can be grouped into 3 groups of 4 bits:

1001 0111 0100

9 7 4

This gives us the hexadecimal number:

97416 = 974H


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A table providing decimal, binary, and hex equivalents for the first 16integers is:

decimal binary Hex0 0000 01 0001 12 0010 23 0011 34 0100 45 0101 56 0110 67 0111 78 1000 89 1001 910 1010 A

11 1011 B12 1100 C13 1101 D14 1110 E15 1111 F

A few further examples of binary and hexadecimal numbers follow:

0100 1100 0001 1111 = 4C1F16

= 4C1FH

1101 0110 1100 0000 = D6C016 = D6C0H


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Hardware


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There are 5 Categories of Computer Hardware

These units are all interconnected through various buses.

A bus is a set of wires (a physical path for the signals to travel).


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Output Device

Output Device

Storage Device

Storage Device

Input Device

Input Device Output Device

CommunicationDevice

Processing


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power supply

ports andconnectors

expansion

board

motherboard

expansionslots CPU

memory

hard disk

open bay

open bay

open bay

CD-ROM

floppy drive


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Terminology of Components "Inside" the Box

Power Supply:A power supply regulates the supply of electricity to the variouscomponents of the computer.

Motherboard:The motherboard is the most important part of the system. It acts as the

foundation of your computer and supplies all of the electrical connections

between components.

ROM (Read-Only Memory):Read-only memory contains the commands your computer needs to getitself going. The ROM is non-volitile, meaning that the contents of ROM

are retained even when the power is off. The instructions in ROM allow

the comuter to get started when the power is turned on.

CPU (Central Processing Unit):The CPU is the brain of the computer. The CPU is a chip that actually

processes instructions and carries out commands. Every other part ofyour comuter serves the microprocessor so it can do its job.

RAM (Random-Access Memory):RAM is the working memory of the computer. For instance, when you

run a program, it is loaded from your hard disk into RAM and remains

therre while you use it. You have to save work onto a disk because

whatever is in RAM gets erased when the computer is turned off. RAM

chips are physical components that contain the memory and are grouped inrows called banks.

Floppy Drives:Floppy drives allow you to write information to, and read, floppy

diskettes.

Add-on Boards:Add-on boards, that extend the abilities of your computer. These boardsare inserted into the computers expansion slots. The slots allow you to

add boards such as serial and parallel prots, modems, video cards, mice

and fax boards.

Disk Controler:The disk controller connects the disk drives, floppy or hard, to the CPU.

Without this card, the CPU would not be able to communicate with thedrives, and the computer would have no way to save or retrieve

information.


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Processing Unit

The processing unit is made up of the Central Processing Unit andmemory.

1. Central Processing Unit

Has 3 different parts:

a) Arithmetic/Logic Unit (ALU)* Performs arithmetic and logic operations

b) Instruction Control Unit (ICU)* Coordinates the machine's activities

c) Memory (Registers)* Special memory cells in the CPU that is used

as temporary holding places.* Certain registers are assigned special tasks(e.g. instruction register, storage register,accumulator etc)

2. Main Memory* Stores data and program instructions* each physical storage unit is assigned a unique address* a location in main memory is accessed by its address

To View Bottom View


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Main Memory

There are two parts to the main memory - ROM and RAM

ROM (Read only memory)

Contains BIOS and start-up programs. The BIOS areinstructions to perform many elementary functions such astelling the computer how to "be a computer" and how to "bootitself up" or turn itself on.

ROM memory cannot be altered, and is not cleared when thepower is turned off.

Very slow compared to RAM memory (see below).

RAM (Random Access memory) Control Unit can only directly interact with RAM. Temporary storage that serves as the "working" memory of

the computer. RAM's memory contents can be changed, and are cleared

when the power is turned off (i.e. it's volatile). Very fast memory access.

Communication


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Computer memory is usually characterized by how much storage theycan hold.

Each storage location has an address.

Storage locations can hold instructions or data

The # of locations and size determines how much information canbe kept in memory.

Analogous to a post office and the post office boxes.

The amount of computer memory is expressed in units of bytes.(i.e. 32 MB, 64 MB, 128 MB)

1 Kilobyte (KB) = 1024 bytes1 Megabyte (MB) = 1024 KB's


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The Control Unit Decodes each program instruction, and then executes it by

sending and/or retrieving data to/from memory locations orsections of the computer.

Arithmetic Logic Unit Circuitry to perform +-*/ on only two numbers, or compare

two numbers.

Registers Part of control unit, not memory Very high speed storage locations. Used only in low level programming.

Communication


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The Motherboard

All processing unit components are placed on the motherboard and areconnected by something called a bus.


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So, how does a Computer's CPU actually do something?


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Secondary Storage Units

Non-volatile (compared to RAM)

Cheap per MB (compared to RAM/ROM)

Convenient (compared to filing cabinet)

Relatively fast (compared to filing cabinet)

Slow compared to RAM

There are two main classifications of secondary storage units:

1. Direct Access devices:

Data is located directly according to its address withoutreading through the other data.

Example: magnetic or optical disk drives

Advantages: fast access to data

Disadvantages: easy to erase data

More expensive than sequential devices(see below)

2. Sequential Access devices:

Data is located by reading from the beginning of the media

until the desired data is located.

Example: magnetic tape

Advantages: cheap

Disadvantages: very SLOOOOWWWW retrieval of data


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Types of Sequential Access Storage Units:

Magnetic Tape

Cartridge tape

Types of Direct Access Storage Units:

Floppy Disks

Hard Disks

CD-ROM

Magnetic-Optical drive

PC Cards

Smart Cards


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Formatting a Disk

All Direct Access Devises have to be "Formatting"

Defines the tracks and sectors on the surface of the disk.

Generally erases all data ('cleans' the disk)

Creates FAT (File Allocation Table) and root directorystructure

FAT contains information on sectors for each file plus freesectors

BlockDiskSector

Tracks

This disk is dividedinto 18 sectors.


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Magnetic and Cartridge Tape

Thin plastic ribbon

Sequential storage

Support read and write

operation

Plastic Mylar or Polyester tape covered on one side with a magnetic

coating (iron-oxide) that permits the recording of data

Data can only be accessed sequentially (compare to disk)

QIC (Quarter Inch Cartridges) and DAT (Digital Audio Tape formsare most common now.

Storage 200MB to 10+GB

Useful for:

Are now used primarily for backing-up data and archivingfrom magnetic disks

Distributing large programs


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TAPE ORGANISATION:

QIC records data in narrow tracks along the length of the tape.When the end is reached, the tape reverses direction and data isrecorded on the next track in the opposite direction. This is calledlongitudinal or serpentine recording.

DAT drives use helical scan technology to record data across thewidth of the tape at a 6-degree angle.

Older reel-to-reel tape drives record data across the width of thetape on 9 tracks.


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Floppy Disks

Consists of magnetic "platter" that rotates at speeds ofapproximately 360 rpm

Read and Write heads is in close contact with the surface of thedisk or platter

Usually very low capacity storage (usually around 1.44 MB)

Shutter

Paper Liner

Rigid Plastic Shell

Metal Hub

Plastic Disk

Magnetic Coating


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Hard Disks

Consists of magnetic "platter" that rotates at speeds of 3600+rpm

Read and Write heads 'floats' over the surface of these platters

Usually high capacity storage (range from 40MB to 10GB+)


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Two types:

1. Fixed

What we think of as hard drives inside the computer box


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2. Removable (disk cartridges such as Zip or Jazz disks)

Zip disks:

o Stores 100 - 250 MB;

o This has become a kind of standard because somany have been sold.

JAZZ disks:

o Stores 1 or 2 GB.

Disk Cartridge


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Key differences between floppy disks and hard disks:

Floppy disk: Head is in close contact with surface of the disk

Hard disk: Heads "fly" on a film of air a fraction of a mm above

the disk's surface.

If head touches dirt or the disk then you have what iscalled a "head crash" which destroys the surface ofdisk and disk head.


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CD-ROM

CD-ROM:

o store 650 MB, or 74 minutes of CD quality music (so about9 MB/minute)

CD-R (CD-Recordable):

o these can be burned once. The media cost about $1 eachfor 650 MB, so media cost is negligible.

CD-RW (CD-Rewrite):

o these can be written over. They cost $10 or so each, andthus are a lot more costly than plain CD-R.

DVD:

o store the equivalent of 5-6 CD-ROMs.


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Magnetic-Optical drive

Combines magnetic and optical (laser) technology

Magnetic field changes polarity of spot.

Capacity ~ 500 MB - 2.3 GB


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PC Cards

Very small Most often used with portable computers Can store more than 300 MB of data


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Smart Cards

Credit card-sized devices that contain a microprocessor in thecenter left section.

Microprocessor can store up to 8,000 bytes of information.

Examples of uses -

o Prepaid telephone card

o Employee time and attendance tracking.


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Input Units

Input devices: These are peripheral equipment that allows data andinstructions to be entered into the computer.

Allows the conversion of "human language" into"computer language"

Two types of Input Device Classifications:

1. Direct Machine data input Machines make better input devices

2. Non-direct Human data entry Most often used method

Examples of Direct Entry Input Devices:

o Scanners (OCR - optical character readers)

o Bar code readers

o Microphones/Sound digitizers

o 2D/3D-Digitizers

o Analog-to-Digital Converters (ADC's)

o Voice recognition devices

o Virtual Reality headsets and gloves

o Sensors (pressure and/or heating sensors)

o Others????


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Examples of non-direct Entry Input Devices:

o Keyboard

o Mouse

o Joystick

o Touch sensitive screens

o Light pens

o Others????


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Output Units

Output devices: These are peripheral equipment that allows data fromthe computer to be converted to human readable

forms.

Allows the conversion of "computer language" into"human language"

Two types of Output Device Classifications:i. Hard Copy

Printer Plotter Microfilm Film and VHS/video

ii. Soft Copy Video Display Units (VDU's or "screens" or

"monitors") Voice Sound Cards Another computer

Others?????


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Types of printers:

Impact printersImpact a solid image of a character onto an inked ribbon upagainst the paper.

i. Daisy wheel, band, chain and drum printers(Old technology)

ii. Dot Matrix:Line of solid pins that moves across the page9 and 24 pin printersCan print graphics

Non-impact printersNo physical contact between paper and printing deviceDot matrix concept used to form characters

i. Laser

ii. Ink jet

iii. Thermal


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Types of Video Display Units (VDU's):

Also called screens, terminals, and monitors.

Types of screens:

Most common screencathode ray tube (CRT)

Another screenliquid crystal display(LCD)Gas Plasma


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Most CRT screens use a technology called raster-scan technology.

The electron gun scans left to right/top to bottom across thescreen grid.


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MonochromeMonitor

ColorMonitor


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Communication Units

Communication devices: These are peripheral equipment thatallows data from one computer to be

transferred to another computer.

Allows computers to "talk" to oneanother.

Examples: Modems Network Cards (Ethernet cards) Serial Ports Parallel Ports

SCSI PortsParallel port: used for the printer, external ZIP drives, scanners,

and cameras. These use a 25-pin connector on thePC.

Serial port: used for external modems, mice, and connectinginstruments. Most new ports use a 9-pin connector,but some older ones have a 25-pin connector.

USB: (Universal Serial Bus) a faster and better connection

that lets you changes components on the fly. Thecomputer should recognize the peripheral and notrequire re-booting. The connectors are smallrectangular plugs.

SCSI: (Small Computer System Interface) less commonstandard for computers that requires interface cards

that look like large printer connectors.

Parallel Ports SCSI Port

Serial Ports MIDI Port


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Computers can send information in one of two ways:

1. Synchronous

2. Asynchronous


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Glossary of Terms

ALU

Arithmetic Logic Unit

CPU

Central Processing Unit

DLLDynamic-link Library:

A feature of the Microsoft Windows family of operating systems and OS/2 that allows

executable routines to be stored separately as files with DLL extensions and to be loaded

only when needed by a program. A dynamic-link library has several advantages. First, it

does not consume any memory until it is used. Second, because a dynamic-link library is

a separate file, a programmer can make corrections or improvements to only that module

without affecting the operation of the calling program or any other dynamic-link library.

Finally, a programmer can use the same dynamic-link library with other programs.

DRAM

Dynamic RAM

EPROM

Erasable Programmable Read Only MemoryEmail

Electronic MAIL

FLOPS

Floating Point Operations Per Second

FTP

File Transfer Protocol

GIF

Acronym for Graphics Interchange Format.

A graphics file format developed by CompuServe and used for transmitting raster images

on the Internet. An image may contain up to 256 colors, including a transparent color.

The size of the file depends on the number of colors actually used. The LZW

compression method is used to reduce the file size still further.

GIF images are often only 8 bit colour rather than 24 bit bit.

Can contain hidden information that may be used by special applications.

Can be animations, i.e. contain several images that are displayed in sequence.

HTTP

HyperText Transfer Protocol

IC

Integrated Circuit

JPEG

Joint Photographic Experts Group

Acronym for Joint Photographic Experts Group. An ISO/ITU standard for storing images in

compressed form using a discrete cosine transform. JPEG trades off compression against loss; itcan achieve a compression ratio of 100:1 with significant loss and possibly 20:1 with little

noticeable loss.

LAN

Local Area Network

LSI

Large Scale Integration

MIPS

Millions of Instructions Per Second


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MPEG

Acronym for Moving Pictures Experts Group.

A set of standards for audio and video compression established by the Joint ISO/IEC Technical

Committee on Information Technology. The MPEG standard has different types that have been

designed to work in different situations.

MSB

Most Significant Bit

NFS

Network Filing System

OCR

Optical Character Recognition

PCMCIA

Personal Computer Memory Card International Association

PDA

Personal Digital Assistant

PNG

Portable Network Graphics

A file format for bit mapped graphic images, designed to be a replacement for the GIFformat,

without the legal restrictions associated with GIF

RAM

Random Access MemoryRISC

Reduced Instruction Set Computer

ROM

Read Only Memory

SVGA

Super Video Graphic Adapter

.tif or .tiff

Identifies bit map images in Tagged Image File FormatA standard file format commonly used for scanning, storage, and interchange of gray-scale

graphic images. TIFF may be the only format available for older programs (such as older versions

of MacPaint), but most modern programs are able to save images in a variety of other formats,

such as GIFor JPEG.

URLUniform Resource Location

VDU

Video Display Unit

VGA

Video Graphic Adapter

VRAM

Video RAM

WORM

Write Once, Read Many

WWW

World Wide Web
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