Types of errors

Look through the code and write on chat what is wrong here?

Look through the code and write on chat what is wrong here?

Look through the code and write on chat what is wrong here?

No output
Look through the code and write on chat what is wrong here?

Look through the code and write on chat what is wrong here?

Types of errors
Learning objectives
12.5.3.1 describe execution errors at programme startup
12.5.3.5 describe a syntax error in a programme code
12.5.3.6 describe a logic error in a programme code
12.1C: System testing

Learners will be able to:
Know what different types of programming errors can occur.
Describe different error types.
Be able to recognise errors in program code.
Apply skills to fix the error.
Combine this as part of the testing approach.

Activity 2. Group work (7 min)
Task: Complete the mindmap on topic of error types together
Review the text material about error type,
Discuss in group and highlight 3 features that distinguish it from other types
Give 2 specific examples with code
Share your information with class using mindmap
Error types
Syntax Errors (1-group)
Logical Errors (2-group)
Run-time Errors (3-group)
Latent Errors (4-group)
https://www.mindmeister.com/ru

Syntax Errors
Spelling mistakes
Missing out quotes
Missing out brackets
Using upper case characters in key words e.g. IF instead of if
Missing out a colon or semicolon at end of a statement
Using tokens in the wrong order
Undeclared function definitions
Undeclared variable definitions

Run-time Errors
Infinite Loop
Memory De-allocation
Datatype mismatch
Logical errors
Type-checking errors

Logical Errors
Incorrect Logic
Improper Algorithm to code translation
Miscalculations
Infinite loops

Formal logic (also known as “mathematical logic”) is the flavor of logic that comes to mind when we speak about computers. It’s based on “propositions” or “Boolean variables” that can be either true or false.
IF the user is logged in,
AND the user has the correct permissions,
THEN show the user the configuration page.
IF this exception is uncatchable,
OR we haven't provided a way to handle it,
THEN crash.

Case 1
Case 2
What is the difference?
Why do we have such error?

Exception
An exception is an object that describes an error or unexpected behaviour of a script/code.
User defined functions and classes can also throw exceptions.
Exceptions are a good way to stop a function when it comes across data that it cannot use.

Latent Errors
Latent Errors are the ‘hidden’ errors that occur only when a particular set of data is used.
For example:
result = (a+b)/(c-d);
An error occurs only when c and d are equal because that will make remainder zero (divide by zero error). Such errors can be detected
only by using all possible combinations of data.

How to find and fix errors in the system?
Debugging is the process of finding errors in the source code (detection), understanding why they occurred (diagnosis) and correcting them. Errors are found through error messages generated by the program or the operating system or because the program does not behave as expected.
Desk checking or dry running is the process of checking an algorithm for errors. You do this by pretending to be a computer and executing the steps in the algorithm one by one, while keeping a record or track of the results.
Trace table is a very useful tool which allows you to see the state of your algorithm with as much details as you wish. Each row of the table shows the state of one step in the algorithm and each column shows the value of a variable at that step. The trace table allows you to check the algorithm for errors.

Practice 1. Individual work (3 min)
Find the errors and fix them. Parts 4 - 7
https://www.canyoucompute.co.uk/errors.html

Activity 3. Individual work
Worksheet 1
Worksheet 2

Reflection
Do conclusion on the topic of the lesson. Write 3 sentences at least on teachers padlet wall.
What remained unclear for you?
https://padlet.com/

Pair work
Each student writes some lines of code containing a syntax or logical error for their partner to debug.
Partner finds and fixes this errors.

Useful links
https://docs.microsoft.com/en-us/azure/azure-sql/database/troubleshoot-common-errors-issues
https://www.stickyminds.com/article/logic-and-software-testing
https://www.geeksforgeeks.org/php-types-of-errors/
https://www.geeksforgeeks.org/errors-in-cc/