Upload
angelica-lynette-day
View
221
Download
0
Embed Size (px)
Citation preview
BTEC Unit 06 – Lesson 08
Principals of Software Design
Mr C JohnstonICT Teacher
www.computechedu.co.uk
Session Objectives Understand the principles of software development, Understand the principles of software structure.
System Development Lifecycle
Developing software is a complex process which requires a number of stages to ensure that it is successful and does what it is supposed to do,
We break the process of developing software down into a number of stages known as the system lifecycle,
Each stage has a specific focus to ensure that the next stage can be completed,
Much of the early work is done is done by a systems analyst rather than a programmer.
System Life Cycle When developing software we follow the stages in
the system lifecycle in order to complete it......
IdentifyOutline of the
problem
AnalyseThe needs of the system
Evaluate / MaintainRefining the system
DesignPlanning all parts of the system
ImplementCreating the system
TestMaking sure the system works
System life cycle
Stages Identification of Problem
Define the scope Analysis
Gather user requirements Create Specification
Design User interface Structure of program Procedure design Data structure design
Implementation – Write Program Testing Evaluation and Maintenance
BTEC Book – Unit 06 p14-16 Section 2.1
Software Structures The structure of the program depends on the type
of programming language been used… Procedural splits into procedures or functions whilst
in OO programs are spilt into objects which are based on classes.
Programming terms… Functions, Procedures, Classes and Objects, Predefined
Code.
BTEC Book – Unit 06 p16-18 Section 2.2
BTEC Book – Unit 06 p14-18 Section 2.1 and Section 2.2
Presentation – Tools Used During the Investigation, Analysis and Design Stage
Creating High Code Reliable and Robust
Can deal with user errors Usable
Programs need to be intuitive Portable
Ability to run on different hardware and software platforms Maintainable
Make sure that the programs written have documentation and are easier to read
Efficient Code Using loops to repeat code instead of writing the same thing
several times one after the other Using subroutines to repeat code common to several sections of a
program Using CASE statements instead of nested IFs
Suitable Design Defining correct data types to store things Defining variables in the correct place – as locally as
possible so don’t bloat other routines, Use predefined code and functions where possible to save
writing their own.
Making Code Easier To Read
Using the comment facility to add comments to the programming code,
Using appropriate names for variables,
Indent blocks of selection and iteration code.
Use a software development application rather than a text editor,
Colour codes different parts of the code to make it easier to read.
BTEC Book – Unit 06 p18-20
• M1 and D1 are best combined as the topics are related.• To cover M1 adequately you need to make sure you explain all the quality
issues from the unit content (efficiency, reliability, robustness, usability, portability, maintainability). Remember for a merit criterion you need to provide more than a descriptive list – You need to explain why the issues discussed are important when developing software.
• For D1 again a descriptive list of techniques to make the code easier to read is not enough to cover this criterion. You need to discuss the issue involved, the benefits and limitations of each technique. Give examples of actual code showing the technique in use and explain what issue may arise if it is not used.
P5 – Explain the role of software design principal and software structures in the IT Systems Development Lifecycle,M1 – Explain the importance of the quality of the codeD1 – Discuss factors which can improve the readability of the code
P5 – Explain the role of software design principal and software structures in the IT Systems Development Lifecycle,M1 – Explain the importance of the quality of the codeD1 – Discuss factors which can improve the readability of the code