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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
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1
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Protot
ping
!
irst att"
mpt at ad
"
sign -"
n#
an$ "
dt
#
ro%
g#
it"
ration syst"
m$
an b"
$
#
ang"
d accoringto
!
" "
dback giv"
n
eval%
ate proposals -no discriptions
req%
ired.
tak e place atdi
! !
erent stades -maxim
%
m!
eedback
allows designer to!
%
lly meet needs
Excessivedeveopment time o
!
prototype
design options problems and possible sol
%
tions
Evol&
tionary �1st is made and eval
%
ated by end
&
ser
�2nd made and eval%
ated
�last one meets all req.
T'
rowAway
�vario%
s parts made
�t#
ese are not%
sed, t#
ey're t
#
rown away
�give and recieve q%
ick (
eedback
�small changes wo&
ld req&
ire large effors.
improved q%
ality
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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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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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
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