Evaluation

Learning Intentions

Describe and exemplify evaluation of a solution in terms of: fitness for purpose, efficiency, robustness and readability.

Success Criteria

I am able to describe the terms: fitness for purpose, efficiency, robustness and readability and how these relate to software development

Fitness for purpose

Fitness for purpose is how well a program fulfils it original functional requirements.
The functional requirements were agreed at the analysis stage by both the developer and the client.
If any of these requirements are not met, the software is considered to not be fit-for-purpose.

A program is written to take in 20 numbers. It must then ensure that the numbers are between 0 and 100 (inclusive). The program then displays the average of these numbers. The program is written as below. Is this program fit-for-purpose or not and why?

Try it yourself

total = 0

for i in range(20):
  print("Please insert number", (i + 1))
  n = int(input())
  total = total + n

average = total / 20

Try it yourself

total = 0

for i in range(20):
  print("Please insert number", (i + 1))
  n = int(input())
  total = total + n

average = total / 20

Efficiency

Efficiency is, without any doubt, the most crucial component of large-scale software development.
Any software that is inefficient needs improved to improve efficiency and ensure that the software doesn't waste time and resources.
Think about something like Windows where time is very important.
Think about when you use Python. Do you want a loop to take as little time to complete or as much time as possible?

Efficiency

Inefficiency can normally be outlined as:
- Not using loops to repeat something over and over again
- Where an algorithm such as a running total could be used to make the code easier to implement
- Using a fixed loop where a conditional loop may have been better
- Not using an array where appropriate

Inefficiency examples

number1 = int(input())
number2 = int(input())
number3 = int(input())
number4 = int(input())
number5 = int(input())

total = number1 + number2 + number3 + number4 + number5
print(total)

Using an array

Using a loop

Using predefined functions

This can be made more efficient by:

Using a conditional loop

Using a fixed loop

Inefficiency examples

print(0)
print(2)
print(4)
print(6)
print(8)
print(10)

Using an array

Using a loop

Using predefined functions

This can be made more efficient by:

Using a conditional loop

Using a fixed loop

Inefficiency examples

for i in range(0, 30):
  print("Please insert a number")
  if n > 50:
    print("You gave me a number > 50")
    break

Using an array

Using a loop

Using predefined functions

This can be made more efficient by:

Using a conditional loop

Using a fixed loop

Robustness

Robustness is another way of evaluating software.
A robust program should be able to cope with errors (or exceptions) during runtime.
Input validation allows us to check that the value the user has inserted is within the range and is also valid.
For example, imagine a program that takes in two numbers. The user then types their name for the first number. What would happen as a result of this?

Other ways of dealing with exceptions

Try and Except can be used to deal with exceptional data too.
Whilst it is beyond the scope of the National 5 course, it is useful to know that the industrial standard of using try and except to stop errors (exceptions) interfering with the running of the program.

try:
  x = int(input())
  print(x + 5)
except:
  print("Cannot add the numbers together. Are you sure you provided an integer?")

Readability

Readability is all about how easy the code is to understand.
There are four ways discussed at National 5:
- Comments
- Meaningful identifiers
- Indentation
- White space

Comments

Comments are something you should all be doing at National 5.
The most important comment that should be in every program that you write is the first comment which describes what the program does.
To comment your code you use the # sign at the start of a comment.

#Program to calculate the average
#Written by J Balfour 2020

Meaningful identifiers

Identifiers are names given to variables and functions (both known as first-class citizens)
A meaningful identifier is one that describes the purpose of it within it's name.
You can use underscore case or camelCase when you are writing variable names or subprogram names (at least, in Higher, that is)
Variable names and subprogram names cannot be keywords in Python.

def john:
  alice = 10
  bob = 20
  
  zelda = alice + bob
  return zelda

iNDENTATION

Indentation is used to show the structure of a program.
Python enforces indentation and is one of the only languages to do this.
When you write an if statement, you'll notice the lines after are indented.

if c > 10:
  print("This line is indented")

Lookup the rules for identifiers in Python. For example, can they start with underscores?

Task

White space

White space is another way of making code more readable.
White space involves creating sections of the code with no content. For example, spacing out lines by adding a blank line after each line.
White space is employed in website design to make a website more readable, too.

Answer the questions on software evaluation

Task

Past Paper Questions

Try out the following past paper questions:

2018 Question 21(b)(ii)
2021 Question 12(c)
2022 Question 8(c)(iii)