Example: IPO Charts and Pseudocode

Your old primary school teacher has heard that you are studying Software Engineering and has approached you with a request for help.

‘My Year 4 maths class are learning about different types of triangles and I would like some educational software that would help them identify each type.’

In discussion with this ‘client’ you have familiarised yourself with the rules for identifying triangles:

• All triangles have 3 sides.

• Equilateral: equilateral triangles have 3 equal sides and 3 equal angles of 60°.

• Isosceles: isosceles triangles have 2 equal sides and 2 equal angles.

• Right-angled: one of the angles is a right angle (90°) in right-angled triangles.

• Scalene: scalene triangles have no equal sides and no equal angles.

Specification 1: To keep your software simple and age appropriate you will keep the entry of data into the software as the length of each side of the triangle:

• Side a=?

• Side b=?

• Side c=?

Specification 2: The user will click a button labelled "What type of triangle has these sides?" to reveal the triangle type and the reason why it is classified as such to reinforce the key facts.

IPO Chart

A useful tool to understand the problem and clarify the design is to use an IPO (Input, Process, Output) chart.

Step 1: Start with the output - specify what the program is required to do.

Step 2: What are the inputs you need to get to the output?

Step 3: What processes will change the inputs (calculate/combine/collate) to get to the output?

Processes

The processes used to turn inputs into outputs at the fundamental level are;

• Sequence - step by step commands

• Selection - binary IF statements or multiway.

• Iteration - looping (counted, pre- or post-test loops).

These processes can be combined in many ways to solve most problems.

Process 1

Check for Equilateral Triangle

An equilateral triangle has all three sides of equal length.

Logical Check: If a=b AND b=c then the triangle is equilateral.

Process 2

Check for Isosceles Triangle

An isosceles triangle has at least two sides of equal length.

Logical Check: If a=b OR b=c then the triangle is isosceles.

Process 3

Check for Scalene Triangle

A scalene triangle has all sides of different lengths.

Logical Check: If a<>b AND b<>c AND a<>c then the triangle is scalene.

Process 4

Check for Right-Angled Triangle

A right-angled triangle satisfies Pythagorean theorem.

Logical Check: If a^2 + b^2 = c^2 where c is the length of the longest side of the triangle.

Processes as Algorithms - Pseudocode

We use pseudocode in the design phase to represent how an algorithm will function without having to program and test it. Pseudocode is a great tool for simplifying our algorithms in plain language.

We will complete more activities on this later, but for now, here are a few examples of the above program:

Process 1

BEGIN Equilateral
    Get SideA
    Get SideB
    Get SideC
    IF SideA = SideB = SideC THEN
        Display “Equilateral triangle”
    ENDIF 
END Equilateral 

Process 2

BEGIN triangle
    Get SideA
    Get SideB
    Get SideC
    IF SideA = SideB OR SideB = SideC OR SideA = SideC THEN
        Display “Isosceles triangle”
    ENDIF
END triangle

Process 3

BEGIN triangle
    Get SideA
    Get SideB
    Get SideC
    IF SideA <> SideB <> SideC THEN
        Display “Scalene triangle”
    ENDIF
END triangle

Process 4

BEGIN triangle
    Get SideA
    Get SideB
    Get SideC
    IF SideC^2 = SideA^2 + SideB^2 THEN
        Display “Right angle triangle”
    ENDIF
END triangle