Design

Learning Intentions

Describe and compare different means of software design

Success Criteria

Be able to describe and use structure diagrams, flowcharts and pseudocode.

Design notations

There are 3 different design notations that we need to know at National 5. These are:
- Structure diagrams
- Flowcharts
- Pseudocode

Design notations: Structure diagrams

A structure diagram uses a variety of standard symbols with text to represent the order of events required to solve a problem.

Design notations: Structure diagrams

total = 0

for counter in range (0, 10):
  print("Please insert a number")
  number = int(input())

  while number < 0 or number > 10:
    print("Try again")
    number = int(input())

  total = total + number

print(total)

Structure diagram Symbols

Design notations: Structure diagrams

for counter in range (1, 6):
  print(counter)

Design notations: flowcharts

A flowchart uses a variety of standard symbols with text to represent the order of events required to solve a problem.
Flowcharts aren't just used in software design

Design notations: flowcharts

Special symbols represent each different action or control sequence in the code.

Class task and discussion

Create a flow chart or structure diagram for making a cup of tea.
Create a flow chart or structure diagram that loops, asking the user for a number each time and adding it to a total variable, until the user types in 0. Extension: try creating this in Python.
Create a flow chart or structure diagram for taking in 10 grades and verifying they are between 0 and 100 (inclusive) and adding them to an array.

A cup of tea - flowchart

A cup of tea - structure diagram

Pseudocode

Pseudocode is a kind of structured English for describing algorithms and intended for human reading.
It is a textual design notation.
It can look like code but it doesn’t have the same strict syntax.
We should start by thinking about the main steps to solve a problem. We should then refine the steps so we have one line of pseudocode for each line of program code.

Pseudocode example

Lets consider calculating the volume of water in a swimming pool.

What would be the main steps for the problem?

Main Steps

Ask user to enter dimensions of pool in metres

Calculate volume of pool

Display message stating the volume of the pool

Pseudocode example

How would we refine these main steps?

Main Steps

1. Ask user to enter dimensions of pool in metres

2. Calculate volume of pool

3. Display message stating the volume of the pool

Refinement

1.1 Ask the user to enter the length of pool

1.2 Ask the user to enter the width of pool

1.3 Ask the user to enter the depth of pool

2.1 Volume = length x width x depth

3.1 Display "The volume of the pool is", volume

Wireframes

Wireframes are not just used in web!
A wireframe is a diagram or sketch of the input and output screens with which the user will interact.
The wireframe should contain placeholders where data is to be input and labels next to where the output will be.
It should also include relevant buttons to submit the data.

Past Paper Questions

Pseudocode was used to design the program. State another technique that could be used to design the program.

1 mark

2019 Q9(a)(i)

Past Paper Questions

Sam is creating a program to calculate and display the total cost of laying new flooring. Flooring is charged at £15 per square meter and skirting boards are charged at £60 per room.

The total cost is calculated by multiplying the total floor area by 15, then adding the number of rooms requiring skirting multiplied by 60.

Using the information above, design a user interface for the program.

3 marks

2022 10 a)

Past Paper Questions

2022 Q6 a) i)

Line 3 RECEIVE score FROM KEYBOARD
Line 4 IF score = 5 OR score = 10 OR score = 15 THEN
Line 5 IF NOT(score >= 3 AND score <= 12) THEN
Line 6 SEND "Success" TO DISPLAY
Line 7 END IF
Line 8 END IF

State the score that should be input in Line 3 to display ‘Success’.

1 mark

2022 Q6