AS Computing – F452 Designing Solutions to Problems

3 Key Stages to Program Design Designing the User Interface Designing the Data Designing the Processing

The method where the user tells the device what to do and the device responds.The method where the user tells the device what to do and the device responds. – Computer – Mobile Phone – ATM – Sat Nav User Interface

Command Line Interface (CLI) Menu Driven Natural Language Graphical User Interface (GUI) Types of Interface

Purely based on command setsPurely based on command sets Difficult to learnDifficult to learn Technically orientated systemsTechnically orientated systems Command Line Interface DOSUNIX

Menu Driven Easy to useEasy to use Require little technical knowledgeRequire little technical knowledge Limited to the options availableLimited to the options available

Enter commands in sentence structureEnter commands in sentence structure “Hello computer, create a spreadsheet with income and expenditure to calculate my monthly outgoings…““Hello computer, create a spreadsheet with income and expenditure to calculate my monthly outgoings…“ Difficult to construct. Human language is very ambiguousDifficult to construct. Human language is very ambiguous Artificial Intelligence of computer systems is not developed enoughArtificial Intelligence of computer systems is not developed enough Is used to some extent in Sat Nav car systemsIs used to some extent in Sat Nav car systems Natural Language

First developed commercially by Apple in the early 1980’s Graphical User Interface

Windows Graphical User Interface Icons Menu Pointers

``Advantages Commonly usedCommonly used Easy to learnEasy to learn Require limited trainingRequire limited training IntuitiveIntuitive Fewer mistakes can be made when using the program Use of GUI objects such as drop downs, option buttons, dialogue boxes to alert on validation errors User can associate icons with real world objects – eg Filing Cabinet and recycle bin Advantages of GUI

Disadvantages of GUI Disadvantages Require more processing power and system resourcesRequire more processing power and system resources Not always suitable for the environment it is being used inNot always suitable for the environment it is being used in Can be restrictive for more advanced usersCan be restrictive for more advanced users

Factors to consider when designing a user interface… The userThe user Screen layoutScreen layout ValidationValidation Online helpOnline help ReadabilityReadability Choice of fonts and coloursChoice of fonts and colours Technology PlatformTechnology Platform Designing a User Interface

HelpHelp ConsistencyConsistency Clear LayoutClear Layout ClarityClarity NavigationNavigation CustomisingCustomising Well designed user interface

Designing Report Layouts Similar factors to a user interface

Data Requirements When designing software you need to specify what data is needed and who it will be stored.

Data Dictionary Contains descriptions and details of data used Eg. Field Name, Field Data Type, Size, Validation

Modular Design Top-Down Stepwise Refinement Advantages to Top-Down modular design Smaller modules – each one is easy to write and test individually Different programmers can work on different modules each Modules can be reused easily

FlowchartsFlowcharts Useful to design algorithms

Pseudo Code Structured English Half English – Half programming Useful to get order of events before beginning coding x=0Repeat x = x + 1 x = x + 1 Print x Print x Until x = 10 x=0Repeat x = x + 1 x = x + 1 Print x Print x Until x = 10

Rapid Application Development RAD Method for designing and programming software. RAD is a method for designing software Where a prototype with reduced functionality is produced Then tested and evaluated by end user Next prototype is refined This process is repeated (with a more refined prototype each time) Until Prototype is accepted by end user Final product is produced based on prototype

RADRAD Spiral Method of system life cycle Iterative Development End user is more involved in software development, so it should be more suited to their requirements

Advantages of RAD Involvement of end user Programmers can tailor make the software specifically for the end user. More feedback. Prototyping irons out any bugs or flaws in the requirements of the software Quicker to develop final product

Disadvantages of RAD Not always suitable for large scale software projects. Prototype maybe very different to what is actually required. May not produce the most efficient solution if processing large volumes of data Software produced often inefficient due to over-emphasis on the end result.