1. Coding Concepts (Standards and Testing)
Topic 2: Programming
Coding Concepts (Standards and Testing)

2. Programming Standards
Whenever we program in specific languages, there are always standards we can try and stick to
These standards describe
What capitalisation to use for variables/functions/classes
Where to make curly braces
What comments to include
We don’t have to adhere to these standards at all
However, they do make program code easier to read for other programmers
Programming: Coding Concepts (Standards and Testing)

3. Programming Standards: Python
Python is the easiest to understand standards for
It has one rule
All variable/function names are in lower case, and use underscores between words
Programming: Coding Concepts (Standards and Testing)

4. Programming Standards: C#
In C#, we have one key standard for variable/function names
Each word in the name starts with a capital letter
However, local variables in C# (i.e. ones made in a function) start with a lower-case letter
Then use capital letters for every word thereafter
Functions in C# skew this standard slightly
And always start with a capital letter
They call this naming standard CamelCase
Programming: Coding Concepts (Standards and Testing)

5. Programming Standards: Java
Java and C# are nearly identical in the standards department
The only difference is that both variables and functions in Java use the ‘lower-case first letter’ naming standard
Programming: Coding Concepts (Standards and Testing)

6. Programming Standards
Another thing to note about names of functions/variables
Try and make their names descriptive
Do NOT use i, x, y, and so on for variable names
They need to describe, at least a little, what the variable is used for
For example, if a variable is being used as the index in an array, use currentIndex/current_index instead of i
Programming: Coding Concepts (Standards and Testing)

7. Programming: Coding Concepts (Standards and Testing)
Comments
The other thing we can do to make our work more readable and understandable is to add comments
Comments can help explain why a certain sequence was used, or what parts of the program do in general
Whenever we create a program, we should always comment our work
But not over comment it
Programming: Coding Concepts (Standards and Testing)

8. Programming: Coding Concepts (Standards and Testing)
Comments
First, we need to see how we can add comments
In C# and Java, we can include two different types of comment
Inline comments (using //)
Block comments (using /* to start, and */ to end)
We’d use inline comments to explain why certain expressions/sequences were used in a function
We’d use block comments to explain what a function/program does
Programming: Coding Concepts (Standards and Testing)

9. Programming: Coding Concepts (Standards and Testing)
Comments
In Python, we use # for inline comments
Also, technically block comments don’t exist in Python
If we really want them, we can use multi-line strings
Started with “““ and ended with ”””
Programming: Coding Concepts (Standards and Testing)

10. Programming: Coding Concepts (Standards and Testing)
Find two programs that you have made previously
Add inline/block comments to describe/explain
What the program does
What certain sequences are doing
Why certain values were used
Try and make your comments descriptive!
Also, change any variable names used if they are not descriptive
Programming: Coding Concepts (Standards and Testing)

11. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
Programmers are not infallible
We very often make mistakes
Some small, some big
Whenever we make a mistake in a program, one of two errors can happen
Syntactical errors: these stop the program from running
Also known as compile-time errors
Semantic errors: these cause the program to crash/behave oddly while it is running
Also known as runtime errors
Programming: Coding Concepts (Standards and Testing)

12. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
When creating programs, we will need to deal with these issues regularly
The easiest one to deal with is the syntactical/compile-time error
Depending on the Integrated Development Environment (IDE) we use, we may be shown ‘hints’ of where the error is
Usually appear as red underlines
Some IDEs even show a hint of the exact problem when we hover over it
Programming: Coding Concepts (Standards and Testing)

13. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
Whenever we see these, we need to work out what went wrong
Common problems are
Missing semi-colons (for C# and Java)
Incorrect indentation (for Python)
Missing/too many brackets
The program won’t run unless all these errors are gone
Programming: Coding Concepts (Standards and Testing)

14. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
Semantic/runtime errors are a little trickier to deal with
That’s because they don’t show up as red underlines in the program code
The error happens while the program is running
There are two ways in which these errors manifest
Bugs in the program (meaning the program doesn’t crash)
Program crashes (where the program stops completely)
Programming: Coding Concepts (Standards and Testing)

15. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
Program crashes are a lot easier to deal with
Depending on the IDE, a message can appear in the console area
This message may include detailed comments on
What the error is
Where the error happened
Programming: Coding Concepts (Standards and Testing)

16. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
If the program crashes completely, we should see something called a stack trace
This is the stack of current functions being executed
We’ll also see the specific runtime error near the top
Common ones include StackOverflow, ArrayIndexOutOfBounds, and NullPointer
The name of the error usually gives us a hint as to what went wrong
ArrayIndexOutOfBounds: we used an index for an array that wasn’t valid
StackOverflow: a recursive function is running itself too much
NullPointer: we haven’t given a variable a value yet
Programming: Coding Concepts (Standards and Testing)

17. Programming: Coding Concepts (Standards and Testing)
Debugging Programs
If the program didn’t crash, but behaved oddly, then we have a bug on our hands
These are trickier to deal with, as we won’t often be told why the bug is there
The best thing to do is work through the program code with a trace table and see if it shows where the error is
Programming: Coding Concepts (Standards and Testing)

18. Programming: Coding Concepts (Standards and Testing)
Testing Programs
The final thing we should be able to do with our programs is test them
We’ve seen testing before
Using a trace table
If we have the program at hand, we can just run it using different values of input
However, when testing programs, we need to test every possible location where input is allowed
Not just the start of the program
Programming: Coding Concepts (Standards and Testing)

19. Programming: Coding Concepts (Standards and Testing)
Testing Programs
When testing programs, we can use three different sets of data
Normal Data: the usual, valid data we may input
Boundary Data: valid data, but the absolute smallest/highest/most extreme accepted value
Erroneous Data: data that is invalid
We need to use each type of data when testing programs
To ensure the program behaves correctly for each one
Programming: Coding Concepts (Standards and Testing)

20. Programming: Coding Concepts (Standards and Testing)
Testing Programs
To test the program, we come up with a test plan
This plan lists
All the possible places where input is accepted
The normal, boundary, and erroneous data to test with
The expected output of using each piece of data
The actual output from using each piece of data
The result of the test (e.g. PASS or FAIL)
Programming: Coding Concepts (Standards and Testing)

21. Programming: Coding Concepts (Standards and Testing)
Testing Programs
This test plan can be written in a table form
Like the example below
Program asks user if they would like to play another game
Test
Data
Input Value
Expected Outcome
Actual Outcome
Result
When asking user if they want to play another game
Normal
“yes”
Program continues
FAIL
Boundary
“no”
Program stops
Erroneous
“25”
Asks question again
Programming: Coding Concepts (Standards and Testing)

22. Programming: Coding Concepts (Standards and Testing)
Create a test plan for the programs you commented earlier
Find every possible place where input is accepted
Come up with a test for all types of data
Normal, boundary, and erroneous
Make sure to state the expected outcome and the actual outcome as well
Programming: Coding Concepts (Standards and Testing)