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P5, M1, D1. Explain where software design structures fit into the systems development life cycle. (P5) Explain the importance of creating program code.

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Presentation on theme: "P5, M1, D1. Explain where software design structures fit into the systems development life cycle. (P5) Explain the importance of creating program code."— Presentation transcript:

1 P5, M1, D1

2 Explain where software design structures fit into the systems development life cycle. (P5) Explain the importance of creating program code which is of high quality. Describe how the code quality can be improved. (P5, M1) Discuss the ways in which a programmer can make codes easier to read. (D1) Where possible include examples of the methods for improving the quality and readability of program code.

3 The software development Life cycle The SDLC is a process divided into a number of stages. – there are usually 6 stages 1.Gather user requirements: understanding the scope of the project 2.Create specification: identifying the requirements 3.Create design: designing the system 4.Write Programs: writing (coding) the programs 5.Test programs: testing the programs work properly 6.Maintain system: maintaining the system once it has begun to be used.

4 Designing the system The software design and structure fit within the 3 rd stage of the SDLC, that is the……. You will need to draw up a design for the program which defines: – The user interface that will be provided: this might include designs for the screens that users will use to input data and the reports that will be output from the system. – The general structure of the program, including how it will be broken up into procedures and how those procedures will relate to each other (Structured Diagrams) – The detailed design, showing how each of the procedures will carry out their required tasks (structured Diagrams) – How data will be stored by the system, including the variables that will be used and the file structures required (Data Dictionary)

5 Designing the system

6 P5, M1, D1 - Readability Programmer comments: you have already demonstrated this within the program you created in C++. – Explains what that line of code does – Makes it easier for other people to read – Important if modifications needed to be done by other programmer in order to maintain and fix bugs Using appropriate names for variables. Example using ‘Length’ instead of ‘a’. Again you have demonstrated this within the codes you created. – Programmers recommend prefixing the variable name with its data type. E.g. integer variable called Points might be names IntPoints Using indentation: this is normally used to indicate when a loop or selection starts and ends making it easier to read.

7 P5, M1, D1 – Quality of Code Reliable and Robust: Although you might imagine users will use the program in the way it was intended, sometimes they may misuse it. For example, users may make a text input where a numeric one is expected. A well written robust program will be able to cope with such a user error and display an error message rather than crashing. The best way to ensure a program is as robust as possible, is by thoroughly testing it to ensure it works properly and can cope with being used incorrectly. Usability: the best programs are easy to use and intuitive. There are some easy things you can do when designing the user interface to make program easier to use. Clearly labelled controls (Buttons, text boxes etc.), logically arranged controls (that is arranged in order they are likely to be used) and controls grouped by function all make it easier for the user to figure out how the program is to be used.

8 P5, M1, D1 – Quality of Code Portability: this is the ability of a program to run on different hardware or software platforms. This maybe important for some systems. Java for example can run on multiple platforms. Maintainability: every commercial software product needs to be maintained with updates, bug fixes and new features. There are a number of things that can be done to make software easier to maintain. – These include: good detailed technical documentation describing the design and implementation of the software. – Well written programs- which we looked into earlier


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