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L2 Unit 18 Software Design A1 P1, P2 and M2
Transcript of L2 Unit 18 Software Design A1 P1, P2 and M2
Object orientated programming is when multiple instances of the code are created within in the same environment in order to interact with each other. It is used when methods like procedural programming become too complex.
It makes it easier for programmers to create and edit codes while they are programming.
Event driven programming
Event driven programming responds to user input and not how the program is structured. This way, event driven, can be written using the procedural programming approach and the object oriented method.
Event driven programming is used with operating system as it responds to user input. When a button on the program has been used by the user, a certain function from the program will take place and then an option is carried out. Therefore it is written in procedures that will take action when input from a user has taken place.
There are two different types of script languages:
A macro is a small program that is used to carry out actions in other applications. Programs like Word and Excel use macro programs to perform repetitive tasks within the documents.
Web page scripts:
Web page scripts are small programs within web pages that carry out task related to the web. Most scripts consist of validating a users input and opening pop up on a web page. One of the most common scripting language is Java.
Procedural programming is when the instructions are written in a series of logical steps.
The benefits of using this form of programming is that the instructions to the program do not need to be duplicated depending on the amount of tasks that need to be carried out by the program.
Object is when the procedure combines the functions and the data needed together to create the object.
The object is based on a real thing that the program can deal with. Like a library or mail order system.
A class is a template that defines each object of a class. This can categorise data and defines certain traits of the object. It's like the basis of a search engine that can search for something based on the class which is the part you have chosen to search.
Because operating systems like Windows are now used by many, a lot of the programming languages used today are known as visual languages.
Visual languages have a user interface that uses many standard features that are known to a PC user. Buttons, dialog boxes, menus and scroll bars are already built in to them, so the programmer has a much easier job at the design of his/her program and doesn't need to create the program from scratch. They normally support event driven procedures.
These can be more restrictive than designing from scratch but are a lot faster and easier to use. A popular example of a visual language is Scratch.
The best known example of a markup language is HTML which is used to format web pages. HTML is not the same as usual programming because it does not support the same features as usual programming like selection structures and loops. HTML is a way in which a text should be displayed on a browser and allows you to use graphic images, links and other features.
HTML and markup languages use 'tags' which are very readable and easy to understand.
When a program performs calculations, accepting user input and outputting data, instructions are followed from top to bottom. When running the program, no step can be skipped in the sequence. Selection is used when programs need to do different things. Sequence is applied to structured features like videos and audio.
Most selection programming is performed using the "if" instruction. The program will use this "if" to compare to the defined variable and will either execute if true or skip the "if" if it is false. Selection is used when logic needs to be applied to the program.
Iteration is when an instruction within a program is repeated. Normally the program would just run and then finish normally but with iteration, loops are inserted to repeat the code. These repeat infinitely until the user stops it. An example of this is used in Java Script when determining the amount of days.
Factors that Influence the choice of programming languages
When it comes to choosing a programming language there are many factors that influence the companies choice:
Staff Training: Some developers could be more skilled in one language than they are in others, which will factor into the over all choice of language.
Limited tools: If a company doesn't have the right tools for one language then this will factor into whether it is used or not.
Development costs: The cost is another factor that could change the final choice. If the it costs too much it won't be used.
Availability: Because of the amount of time it can take to gain a certain level of expertise amongst the staff, availability can influence the choice of programming language.
Expandability: The operating system that the software is being designed for needs to be compatible with the software itself. If the program is being designed for homes and businesses then it will be designed for mac and windows using languages that are compatible with these systems. This is a big factor towards the choice of programming language.