AQA A2 Computing 7.2 Design

Question 1

During the design phase, the systems requirements must be translated from the logical model of the system into the physical model.

This happens in two stages - what are they?

Answer 1

1. System design, aka high-level design

2. Detailed design, aka low-level design

Question 2

High-level design: The outline solution should consist of…

Answer 2

1. The components of the system
2. The user interface, aka a human-computer interface
3. Test cases

Question 3

Systems flow-chart

Answer 3

A high level picture of a physical system

Question 4

What should be considered when designing a user interface?

Answer 4

The type of user - expert/novice/frequent/occasional/young child/technical etc.

User needs and accessibility issues - sight impairment/limited hand mobility etc.

Choice of appropriate input/output devices, including size of screen

Use of colour - alerts/house style

Use of icons/symbols/text

Type of interface - command line/graphical

Type of menu - drop down/full screen/pop up

consistency of design e.g. conventional menu groupings like file-save as

Question 5

Good user interface design provides:

Answer 5

Feedback to the user e.g. save successful

confirmation e.g. before deleting a record

Clearly marked exits e.g. back a screen, home

Online help

Helpful error messages at a level appropriate to the user

Optional keyboard shortcuts

Question 6

Low-level design: The detailed design should consist of…

Answer 6

Hardware specification
Hierarchy charts and structure charts
Design data dictionary
Object diagrams and class definitions
Data structures such as records or arrays
File organisation
Entity-relationship diagrams
Normalised database tables
Algorithms using pseudo-code or structured English
Queries using SQL
detailed design of printed output
Preliminary test plan
Detailed test data

Question 7

The design data dictionary consists of…

Answer 7

Variable name
Data Type
Max size/length (if appropriate)
Validation
Purpose