ict - page 27

8/6/2019 ICT - Page 27

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Table of Contents

Chapter 1 ² The system Life Cycle ................................ ................................ ................................ ................................ ................................ ................. 1

Type chapter title (level 2) ................................ ................................ ................................ ................................ ................................ ............................2

Type chapter title (level 3) ................................ ................................ ................................ ................................ ................................ ........................ 3

Chapter 2 ² Designing computer-based information systems ................................ ................................ ................................ ................................9

Type chapter title (level 2) ................................ ................................ ................................ ................................ ................................ ............................5

Type chapter title (level 3) ................................ ................................ ................................ ................................ ................................ ........................ 6

8/6/2019 ICT - 7


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ate proposals -no discriptions

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erent stades -maxim

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allows designer to!

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lly meet needs

Excessivedeveopment time o

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prototype

design options problems and possible sol

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�small changes wo&

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improved q%

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early clarification -faster and cheaper

development

)

onfusion between the prototype and

finished system

Imporved and increased user involvement

deadline proposed is met

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Testing

Fr0 0

fro1

errors

Proc2

dur2

s cr2

ateth

0

test plan

M0 0

ts d0

sign sp

0

cification

Corr2

ct r2

sultsand works

Confid2

nc2

toend user

Error = human action

Fault = manifestation ofan error (bugs or d

0

fects)

may cause a softwar

0

failur0

0

nsuring th0

softwar0

is r

0

liable

testing d0

p0

ndson risks involved

safety critical system =rigorous testing

compar2

d to a stock control database

r2

liability and qualityincr

0

ases as faults ar0

fixed

Consid0

r oth0

r factors:contractual and legal r

0

q 3

patch2

s r2

lased to solve any bugs 3

Test4

ata

and Plans

Normal5

ata:Everyday and

corr6

ct

Extr6

m6

7

ata:Corr

8

ct 9 upp8

r and lower boundary

Erron8

ous5

ata:Incorr

6

ct, outsid6

boundary @

Test Plan- th8

r

8

quir8

m8

nts,pathways and

validations

may also b6

includ

8

d in th8

docum

8

ntation.

input and outputwill b

6

clearlystated

un8

xp8

cted r

8

sults = r8

-testing

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RequiremnetSpecification

By system analyst

What to do and achieve

User-SoftA

are interaction

Purpose of system

Hardware Software choices

AContract

B

esign Specification

By system designer

Design for data entry form

Purposeof the system

Assumptions; C

imitations; Constraints

Inputs and Outputs -Document and

InterfaceError Messages

House Style/Colour

Sceme

Validation Rules

Test Plan Produced

System Specification

Defines requirements

for the new system

Facilities and Outputs

Developed usingresults from

investigation

Operatingrequi rements

Information requirements - system should provide to

the end user

Volume requirements

General Systems requirements -security, flexibility, ability to

adapt to growth and change

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Pro ject

MaD

ager

PlaD

aD

d coD

trol the whole pro ject

IdeD

tify poteD

tial problems a

D

dissues

Sets deadliD

es for

each stage

RescheduliE

g, time, staff, mo

E

ey.

Oversee pro ject team

ED

sure budget isadhered.

DocumeD

ts are

completedcorrectly

Makes sure all tasks are

completed

System Analyst

Analyse existing system

Investigates cuttent system

Assess feasibility for system upgrading

Develops feasability report

Data capture/ Procedures/ Process data/

ouput/hardware/training

responsible forrequirement specification

liaise with the staff

Documents are completedcorrectly

Makes sure all tasks arecompleted

System Designer

Desiging/ Developing/

Implementing

Analyst and Designer= The Same

Work ing withprogrammers and

the end user

Planning andDesigning the system

confirm the analyst'sproposal (e.g. hardware req.

F

specification forhardware, software, data

and staff resources

Programmer

Creates software

Can be a specialist or

generalist

Develops theapplication system or

modify existing

Creates technical documentation

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Tester

Find any bugs in

the system and rectify

All aspects should be tested

Deliberatly break the system

Use of Test Plan

White Box and Black Box test

Record the resultson a test log

G

PA

Shows relationship between the different parts

All tasks occur in a logical order

Some tasks willdepend on eachother

Enough time mustbe allocated

Allows projectmanager to identify

the critical path

Dependant or Sequential activity

Independant or Parallel activity

Slack time needs tobe built in

GanttH

hart

Showseach task as a block of time

Assists projectmanager in planning

I

verall Time and Pressure Points

AllocatedGoals

Resources (who'sresponsible)

Status (ticking off)

Dependencies

P

ritical Path = longestsequence of

dependant tasks

ERD

Structure

Entities Relationships

Entitiy = Thing. e.g. a

book

Attributes hold the infoabout attribute; e.g.

product number

Unique field = Primary Key

One:One; One:Many; Many:Many

Many:Many must be

brok en down

Foreign Key used tolink tables together

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Create Purchase Order

State Transition Diagram

define every state of the

system diagrammatically

state will change under the influence of the

outside

Shows each state as a location

One or more action may be associated with each transition

ideal to describe the behaviour of a single

ob ject

Limitation: not good with several ob jects

Data FlowDiagram

Flow of data in a system

Input Data into OutputData

Process uses data stores

What and who they interactwith (external entities)

Doesn't show the hardware or software required

D: computerised data store

(f ile on comp)

M: manual datat store (drawer)

Read through information

sort info into clear sections

produce a data flowtable

convert externalusers to external

entities

convertdocumentation to

data stores

convert activities toprocesses

look at the inputsand outputs for each

process

Link each data store and external entity

Link the processes

check for consistency

FlowCharts

Diagrammaticalrepresentationof the

operations/processes

Don't relate very well tothe actual software

system

Different shapes for different actions

sometimes socomplex, they're hard

to follow

must have a 'start' and 'end'

a decision, 'yes' and 'no'

M3 Purchase Order

D3 Purchase Ledger

Purchase Order

Customer

Customer

3

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Batch

Q

arge andidentical data

Bills/Statements/Payroll

No user interaction required

less demand of

processo r- night

delay between collecting data and

recieving output

user interface = code based

Interactive

transactional processing systen

each transaction must befully processed before the

next

data = small, input = k eyboard

Direct user involvement

prevents doulebooking

Real -Time

done at input time

handled within time limit

effects records immediately

time tak en to provide response

must be quick

air traffic control system

system within asystem = mobile

phones

SingleUser

one user at a time

more than oneaccount

multi-taskingshare peripherals

files can be in more than one place

Chapter 2

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Multi-User

More than oneuser at a time

provided by anetwork

manages all requests, nointerference

Peripherals must be shared buy all

users

Multi-Task ing

more than oneprocess

not controlling 2 things at once

fast - appears towork cocurrently

DistributedProcessing

comprimises anumber of computers

each computercompletes part of

the process

results are combined

meet userrequirements

Computer- Human

Prompts - input appropriate

commandR

dustbin; menu

Nature of Input -based on response

of previous input

Methods of Input -keyboard; mouse;

touch screen

Feedback -options; submenu;

can be limited.

Model

HumanPr ocessor

nformaT

on s r eceived

U

hr ougheyes and ear s -

inpuU

passed onT

o work ing memory -

percepT

ualpr ocessor

2 seperaU

e storage systems - visual and

auditory

MHPdraws an analogybetween the pr ocessing and storage with perceptual,

cognitive, motor and memory activities.

visual or audio stimulusbeing

captur ed

application:onscr een flashing cur sor;

audible stimulus (beep)

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HCI

Colour - housestyle.suitibilty, no

clashes, disabilities, intuitive

Layout - consistent, use of original

source, logical, intuitive

Quantity - too muchinfo slows user

down.

Font - clear andeasy

Complexity - errormessages should be

simple,Controls - buttons, forms and menus

Buttons- use ofmacros

Forms - guidance, error messages,

validations

Menus - select action

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Designing an

Interface

Perception -preconcieved ideas; intuitive; colours and

sound

Attention - Uncluttered; logical; obvious; pop

ups; flash; menus; consistent

Memory - consistent; uncluttered

Learning - previousexperience; help;

errors;

y Black berry uses menus and submenus

y iiPhone uses GUI

y SatNav uses natural language. They use speech as an output

Computer

- Human

Prompts- input appropriate

command; dustbin; menu

Nature of Input -based on response

of previous input

Methods of Input -keyboard; mouse;

touch screen

Feedback -options; submenu;

can be limited.

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Mental Models

Previousk nowledge/experi

enceThe way people

process tasks

Based on inputs, inputsbased on sounds,

visuals, experience

RAM, menus, sub-m, file management, generic features

(software)

allow predictionsfor the future

different users =different mental

model

actions matchedusing audio-visual

indicators

final product matches mental

model

user friendly

ensure expectation are met

Speed of learning will be increased

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8/6/2019 ICT - Page 27


Internet

Internet � WWW

Infrastructure providedto connect computers

together

Uses TCP/IP protocol forcommunucation between

devices

Internet - OPEN network

Access to - Email,WWW, IRC, File

Transfer

Intranet

Same services as the internet but within an

organisation(FROG/Fronter)

Authorisation required

Provided through a LAN but inbigger companies can use avirtual network within a WAN

CLOSED network

Internal Email/Webpages/Chat/File Transfer

No one outside cangain information sent

within the organisation(confidentiality)

Extranet

Access to the intranet withauthorisation

Access provided by logging on to a secure

server from awebpage

Registered users canaccess services from

any internet-connected computer

Confidentiallity of the data is

confirmed

Added risk ofhack ing

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Peer toPeer

Network

no central server -own function and share resources

allequivenlantpeers - no leader -

no server

much easier to setup -often found in homes and small businesses

maintained individuallyClient

Server Network

requires at leastone computer

(server)

server - file storage, back up, app

sharing

client computers are all connected to the server via a

switch etc

log in required to

access (swipe, fingerprings)

can log on to anycomputer

lik ely to be more than one server (specific roles)

Anti virus and

backups all done centrally

specialist techinicalstaff required

if server fails client

will lose data

y Client Server

o Back up are centrally, users don·t have to

become involved and Antivirus is done centrally o Network processing is done centrally at the

server

o Data and application are available from any

client

o Security is managed centrally in a structured

manner

o User doesn·t have to install any software

o Servers require a lot of processing power, large

hard disk s, lots of memory very expensive

o If server fails user has no access to data

o Network manager required

o A lot of network traffic slows down other task s

y Peer to Peer

o Each user is responsible for back up

o Antivirus software has to be installed separately o All processing done by each computer longer

o Software has to be installed individually

o Each computer work s separately

o No reliance on a single server

o Can be setup by a reasonable competent

person

o Network traffic is minimal

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8/6/2019 ICT - Page 27


Cable

Copper -Transmitting Data

Coax - 2 Wires

TV industry -Capacity for High

Bandwidth

Outer Cable -

Shield (ReduceSignal Loss)

Modern - twistedpairs of wire

Unshielded - NoEarth Wire (UTP)

can result in databeing lost (higher

frequencies)

STP - Metal shield(high speednetwork s)

Used within aLAN

cheaper than optical - only 100 metres

Electrical Interference - lost

data pack ets

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Optical

Minute glasstubes; reflect

light

Not susceptible to electrical

interference

Bandwidthsavailable are muchhigher than copper

Bandwidths aredeveloping all

the time Servers

Powerful computer that performs functions forclients connected to it

File Server: Stores files on the network. lik ely to

have shared files

Application Server: stores software for use

accross the network. (software for clientsand server) saves storage space, memory and processing poweron client computers

increases the amount of network traffic

Mail Server: manages all emails, allocateall email and to appropriate inbox,

filtering out SPAM, calender, email limit, central address book

Proxy Server: manages accessto the internet. stores webpages

(faster load), a firewall, filterswebpages

Print Server: Access to a printer within a LAN. Reduces processing burden on

client computer. (priorotise jobs, charge users, restrict numbers,

provide reports)

Back up Server: Back up all data on network ; have tape driversconnected to it; scheduled.

Switch: Used to connect several devices together. Enable communication between them. Ports can be controlled and

prioritised. Set up a virtual LAN ² prevents collisions.

Hub: Look s the same as a switch has the same function of connecting several devices together, but it doesn·t sort the

data. It sends the data pack ets to every port that it is connected to. More collisions can occur and it is mor e susceptible

to interception.

WAP: Hub that work s wirelessly. Usually connected to a network infrastructure through a single cable connected to a

switch. Radio signals are sent from the device, received by the WAP and then sent to the network.

: When a WAP receives a signal, it broadcasts it and the receiving device collects the data pack ets. Potential for

hack ers, use of encryption to prevent it.

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Radio

more commonly

knowns as wi-fi wireless enabled laptopscan connect an

organisations network

use of hotspots and home network s

Using NICs to connectwhere cabling would

be expensive.

Mobile phone and PDAs using wireless

game consoles can connect to the

internet and printerscan be connectd

no restrictions for

portable devices

good compatibility

Transfer ratesare constricted

Bandwidth have to be shared

susceptable to hack ing

Fax

A 2D document can be fed and sent

electronically via a telephone line

Quality will be considerably less than the

original

Cost = Cost of a telephone call

Can be sent almostinstantaneously

Confidentiality isnot guaranteed

Typical Use: Advertising; copies of contracts;

diagrams; maps

Facilities: multiple recipients; recieving is

automatic; Block senders; delivery reciept

EMail

Most popular method of

communication

Attach Files; multiple recipients;

instantaneous

Confidentiality can be

maintained.

Quality is not lost.Cost is virtially 0

advertise; newsletter; messages; documents

send and receive; addressbook; forward;

encrypt

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Bulletin Board

Discussion Board -> discuss topics

Used for leasure or business purposes

Discussion Board ->Forum -> Thread ->

Post

Games; Software;

Politics; Education

Post; Create; Read; Search; Subscribe

Tele/VideoConferencing

Enable communicationbetween groups

Meetings; Lessons; VirtualMuseum

Multiple participation and location

shared whiteboards; dialcalls; shared applications

See all participents; control camera

IRC

Socialcommunication

Allows file sharing

Group conversations

Keep a log of conversations

Use of emoticons :)

Invite and Block users

Setting your status

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ADSL

a range of frequenciesare used on an existing copper telephone lineto provide broadband

Downstream is different to upstream ->

asymmetric

Mostly used fordownloading -> more

frequenciesdownstream than

upstream

Takes longer to uploadthan download

much smaller range offrequencies is left available for PSTN

ADSL provides internet access and doesnt

prevent the usage of thetelephone

Affect Bandwidth: Distance from

telephone exchange;AM radio stations; fax machins; electrical

interference

Mainly used at home asno extra installation

required

not in large businesses -more upstream

bandwidth required