2.1.2 - Designing, creating and refining algorithms

What is an algorithm?

An algorithm is a logical step-by-step process fro solving a problem

What are structure diagrams?

Structure diagrams show the smaller tasks of a larger program

They are made by decomposing the program into manageable modules - which are then decomposed even further until you get modules that perform individual tasks

What are the advantages of using a structure diagram?

• coding is easier as you’re only writing code to carry out very simple tasks

• Lots of programmers can work on one program as each module can be written indepentabley

• Easier to test your program as each module can be tested individually

• Individual sub programs and modules can be fixed and updated without affecting the rest of the program

• Able to reuse the sub programs and modules in programs you write in the future

What is this symbol in flow diagrams?

A line - represents the flow from one components to the next

What is this symbol in flow diagrams?

Process - an action

What is this symbol in flow diagrams?

Input / output

What does this symbol mean in flow diagrams?

Decision - a yes / no / truth / false

What does this symbol mean in flow diagrams?

Termination - so the start or end of the process

What are trace tables used for?

Trace tables are ways of testing that a piece of code is working correctly - a dry run of a program used to identify logic errors

What are the advantages of flow diagrams?

• It is easy to see how a program flows. For example, where does following one path as opposed to another take the program?

• Flow diagrams follow an international standard so it’s easy for any flow diagram user to pick up a diagram and understand it.

What are the disadvantages of flow diagrams?

• with a large program, the diagrams can become huge in size and unwieldy to follow

• any changes to the design may mean a lot of the diagram has to be redrawn

What are the advantages of pseudocode?

• As pseudocode is similar to a programming language, it can be quickly and easily converted into an actual programming language

• it is fairly easy to understand, even for non-programmers

• it does not matter if there are errors in the syntax - it is usually still obvious what is intended

• changes to the design can be incorporated quite easily

What are the disadvantages of pseuedocode?

• It can be hard to see how a program flows, for example, where does following one path as opposed to another take the program?

• It can be time consuming to produce.