CW-V1 SDD 0201 Principals of Software Design and Development Introduction to Programming Languages

2 Learning Objectives Revisit prior learning Describe the factors that influence the programming languages. Select an appropriate language for a given scenario Justify the choice of language CW-V1 SDD 020

Quick Quiz Write down all the objects you can think of that we use in Visual Basic Now write down properties that can be changed on these objects Describe what an event is? Now give events that can be attached to these objects Why do we use naming conventions Give naming conventions for a label, a text box, a form and a command button CW-V1 SDD 0203

4 Types of Programming Language Procedural Object-Oriented Visual – event driven CW-V1 SDD 020

Factors that influence programming languages If you were going to choose a programming language to develop software for a large company what would you think about before you bought it? organisational policy; development and maintenance costs; Ease of use The Interface – features and tools it offers Reliability Expandability Availability of trained staff to use or teach others 5CW-V1 SDD 020

Organisational Policy Some organisations have an organisational policy as to which hardware and software is to be used. Eg may choose Microsoft as very large company and need this level of support 6CW-V1 SDD 020

Development and Maintenance costs When embarking on a project some organisations will look at costs. Some languages have a reputation for cutting maintenance time where others don’t! 7CW-V1 SDD 020

8 Procedural Factors Ease of Use Easy to create small programs but larger ones become very complex. Large bank of commands and syntax has to be learnt. InterfaceAll instructions must be typed directly into an editor. Basic help files may be available. ReliabilitySimple programs run reliably, but become less so as more procedures are added CW-V1 SDD 020

9 Procedural Factors ExpandabilityAdding on extra routines quickly leads to messy, unreliable and hard-to-read code Training Requirement The editing environment is very simple and easy to learn – may just be a text editor. However a lot of specialist knowledge in needed as debugging tools and help files will often be very basic and ‘unfriendly’. This can make training from each new language a long, expensive process. CW-V1 SDD 020

10 Object Oriented Factors Ease of Use Can make creating large, complex applications easier as objects, once coded, can be used multiple times in slightly different ways. However the languages themselves and the concepts involved tend to be very complex and difficult to learn. Very difficult to track errors as objects can be closely related. InterfaceUsually a text editor. Later versions of languages have visual prompts, debugging tools and help files which can make the programmer’s life easier CW-V1 SDD 020

11 Object Oriented Factors ReliabilityPrograms are usually very reliable as multi-use objects will have been thoroughly tested. ExpandabilityDesigned for this purpose. Extra objects can be added at any time. Objects can be changed once and will all share the changes Training Requirement Intensive, specialist training needed to begin with but little needed once the concepts have been learnt CW-V1 SDD 020

12 Visual(event driven) factors Ease of Use Designed to be easy to pick up. Becomes progressively more difficult as used for more complex programs. InterfaceStandard Windows controls (e.g. option button, drop-down list) can be placed on a screen. Code is added using a user friendly editor that suggests actions that can be taken with the control and useful key command words. Help files are usually detailed and involve examples. CW-V1 SDD 020

13 Visual(event driven) factors ReliabilityVariable, depending on programmer skill. Mixture of procedural and OO concepts can make code messy and difficult to follow / structure. ExpandabilityBecomes less reliable and harder to manage as more functionality is added although large programs can be created if initially designed that way. Training Requirement Minimal – designed as a non-expert programming tool. CW-V1 SDD 020

Activity Read the scenario Select the type of programming language you think is best Open SDD021 and fill in the headings Justify why you have chosen it in terms of: organisational policy; development and maintenance costs; Ease of use The Interface – features and tools it offers Reliability Expandability Availability of trained staff to use or teach others 14CW-V1 SDD 020

What do you have to do now? Task 1 presentation – now add slides on the following using today's presentation and your scenario notes SDD 021 Describe the factors influencing the choice of 3 types of languages. One of these must be a visual language. Give your reasons for the choice of language (P2) 15CW-V1 SDD 020