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A2 ICT Revision

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Rachel Mulholland

on 14 December 2013

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Transcript of A2 ICT Revision

3.1 Databases
3.4 The User Interface
Image by Tom Mooring
3.3 Software Development
A2 ICT Revision
3.2 Networked Systems
Data Consistency:
is when data is consistent and there is not more than two entries.

Data Integrity:
refers to the completeness and accuracy of the data.

Data Redundancy:
storing multiple times in multiple locations.

Data Independence:
is the type of data transparency that matters for a centralised DBMS.
What is a database?
A database is an organised, structured collection of relevant data. Main features (Tables, Forms, Queries, Reports)
The process of refining the structure of a database to
minimise redundancy

improve integrity.
2 tables
3 tables
4 tables
Entity-Relationships Diagrams (ERDs)
A diagrammatic representation of the relationship between entities.
Databases are designed using ERDs where tables store entities that share attributes.
Database Management Systems (DBMS)
The software used to manage the operation of databases.
Provide an interface between programs
Enable data protection- levels of access, passwords
Facilitate maintenance of data dictionary

Database Administrator (DBA)
A DBA will:
Decide how data is stored and organised.
Ensure data is secure
Ensure new users are given access to appropriate data
A DBMS must allow users to:
Maintain or update tables
Run macros
Allow users to print information
Management Information Systems (MIS)
This is a system which is designed to provide managers with all the information they need in order to run their organisation effectively.
Factors affecting quality of information:
Up to Date
Presented Effectively
Importance of information


decision making on a daily basis.

responding to market forces and the actions of competitors
medium and long term planning
Purpose of a typical MIS:
Convert data into information
Ensure information is communicated appropriately
Sources of Information
Internal Data
This is data whose source and destination are within a single organisation.
External Data
Data created within an organisation then outputted to an external destination
Decision Support Systems
Supports a variety of decision making processes and styles
Assists decision making within dynamic business conditions.
A set of integrated tools designed to help in problem solving

Expert Systems
An application that carries out a task near the skill level of the expert.
Limited to a certain area
Capable of learning from experience
Based around rules, facts and principals
Knowledge Base:
a source of facts, rules and principals from a given field
Interface Engine:
solves a problem by applying the rules and knowledge already in the system to the facts that are entered concerning the problem.
User Interface:
includes menus, graphics and facilities for explaining the systems reasoning
Threats to Data Security
National disasters
Operator error
Threats from the internet
Unauthorised access to premises
Disgruntled ex-employees
Managing security in a DBMS
User ID/ Passwords
Limiting logins
Access Rights and locking
Audit trails
Auditing and accounting:
software automatically maintains a log of all database activity. Changes can be undone to restore the original data.
Disaster Recovery Planning
Def:A self contained section of a security policy that describes how all data can be recovered in the event of a natural or man-made catastrophe
It should:
Ensure all files are backed up at intervals
State how long backups are held
State how and where
State the media used
Backup Strategies
Full Periodic Backup
All data files being copied to a separate portable storage device at regular intervals
Time consuming recovery
Transaction Logging and the Grandfather- Father-Son Cycle
A continuous record of all transactions made on a particular day
Incremental Backup
Involves backing up of all files that have changed at set intervals
Online Backup
Saving work on a primary and a secondary server to provide duplicate storage.
Cannot recover data when it has been lost
Primary Keys
A field that is used to uniquely define a particular record in a table.
Foreign Keys
A field in one table which is the primary key of another.
Used to establish a relationship between the tables.
Recovery Strategies
A disaster recovery strategy should:
state the key business functions to be recovered.
state the contact details appointed to help
state the hardware, software, communications, data, personnel, essential for the business
state the procedures to be followed before, during ,after a disaster
state how parts of the network and files will be restored
Types of Network
Client Server
A client is a program or hardware device that requests a service from a server
Thin Clients:
a computer program which depends heavily on some other computer to fulfil a role.
Fat Clients:
as much software is held on client PCs and a central server is concerned with data storage
initiates data requests from a server
waits for a response + acts on it
connects to several servers simultaneously
waits for clients to request data
may accept connections from many clients simultaneously
doesn't interact with end users
Peer-to-Peer Networks
Made up of nodes that are considered to have equal status
A P2P system:
the requesting peer (RP) sends a request for data to it's neighbours
the request is flooded through network + info about suitable peers is returned to RP
the RP initiates transfer directly from selected peers
downloaded files are held on the RP.
Centralised Database
Easier to maintain
less expensive to install
if a single database fails data may become inaccessible
if someone gains unauthorised access to a central server they gain access to the entire database
Distributed Database
a centralised database is useful to firms based on only one site
in a distributed database computers may be needed at headquarters to maintain sensitive data
Problems associated with remote access:
network response slows when WAN traffic is heavy
data is unavailable when a failure occurs on the network
Mobile and Wireless Communication
Wireless (LAN)
Open Systems Interconnection (OSI)
Detecting and correcting data transmission
Methods of ensuring data security
Terminal Security
3.5 User Support and Training
Data Link
Communication partners identified
Transforms data into a form the application will accept
Establishes, manages and terminates connections between applications
Transfer of data between end systems or hosts
Provides switching and routing technologies
Data packets are encoded and decoded
Provides the hardware means of sending and receiving data on a carrier.
defines a networking framework for implementing protocols
Parity bits
Echo Checking
In each byte, 7 bits=data, 8th bit is parity bit.
At receiving end a check on each byte is performed and if parity has changed the receiver knows an error occurred.

Received data is transmitted back to the sender where it is checked against the original document
No way of knowing how and where the error occurred.
Access rights and Locking
Username and Passwords
Log on restrictions
Terminal locking and Password
prevents users from accessing data they don’t need to access.
form the most invisible part of many systems security.
restricts where the users can log on.
restricting login within working hours.
terminal can be locked. If forgotten a protected screensaver should activate.
make a PC or a network appear to not exist to unauthorised users to gain access through the Internet.
is used to store data that cant be decoded without a password.
The end user is involved in:
It is a linear model
Minimal resources required to implement
Documentation produced at each stage
Cant go back
Until the final stage of development cycle is complete a working model doesn’t lie in the hands of the client
prototype is built to understand the requirements.
Prototype is developed based on the currently known requirements.
Development of the prototype undergoes design, coding and testing
Rapid Application Development (RAD)
Requirements Planning:
combines elements of the systems planning and analysis phases of the SDLC
Project Management
Project planning:
a project must be planned + broken into smaller work tasks with time estimates.

Risk analysis:
must outline the risks: scenarios that could lead to project failing.

Staff availability :
will the right people be available to carry out the tasks?

Budget control:
project must be profitable, all spending must be justified+ development costs under control

People management:
team members must remain motivated and focused on the objective.
Computer Aided Software Engineering (CASE)
Normally contain components for:
Modelling a system: graphics tools can be used to construct DFDs + ERDs
Data dictionary development and control: data dictionary is a file containing a description of data structure
Interface generator: this allows the automatic creation of a user interface such as a menu, dialogue box and report
Developing new software
Off- the-shelf
Errors can be detected earlier
Quicker user feedback
May increase complexity of the system
User Design:
use a combination of JAD techniques and CASE tools
programming, application development, coding and system testing
SDLC implementation phase
Will be aimed at non-ICT specialists- is often used to refer to the user guide
A process of review must be undertaken to ensure its free of jargon.
Will rarely leave the developers unless it's been distributed to a partner firm
The Waterfall Model
Calculated by adding together all the bytes in a packet of data which is sent as part of the data.
It is then recalculated, if checksum is incorrect the data is likely an error
Mobile Communication
This connects computers over a small geographical area.
All network computers are equipped with wireless network interface cards (WNIC).
Radio frequency waves are used for communication information.
When a mobile connects to a network it communicates with the nearest base station.
Accounting Software
Audit Trails
records each event within a system

If a hacker enters a system everything they do is logged

Log files show what someone has did and when – if a person damages data they can be apprehended.

Are needed:

To meet formal or legal audit requirements

For billing purposes

For maintenance reasons

For security reasons
Improves software quality by performing error checking
Will automatically produce documentation
End Users:
People who use computer systems on a daily basis.
European Computer Driving License (ECDL)
Training courses may be specific to the software they are using.
Software licences are often for a set length of time. If a company wants to continue using the package, regular fees must be paid.
Upgrade costs may be unavoidable
Server software upgrades may be required to permit the full functionality of modern applications for effective data sharing via a network.
In-house development
A company has programmers on its staff and develops software internally
Satisfy unique business requirements
Require less technical development staff
Customising a Software Package
Purchase a basic package vendors will customise
Direct negotiation
Paying for the changes
Make your own modifications
software testing continues until agreement reached between developer + purchaser.
final stage before system is accepted. Testing system with data supplied by system purchaser.
package distributed to potential users who test and report faults
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