Errors and Bugs

• Computing
• Lower Secondary (Key Stage 3)

Do Now - What happens if we have errors in our program when we are writing code?

Do now - When you press RUN on a program, what do you think happens inside the computer?

Toxicode

https://compute-it.toxicode.fr/

Nitrotype

https://www.nitrotype.com/

KidzType

https://www.kidztype.com/

The CPU reads each instruction in order line by line, storing and updating variables in memory and waiting for any needed input. It then sends commands to output devices like the screen, any errors/bugs stop the program running or make it behave unexpectedly.

Learning Objective: 

To understand how errors and bugs affect our programs and apply this through identifying, fixing and debugging errors.

Errors

• Errors in programs are often referred to as bugs

• Errors can cause a program to produce unexpected results, or crash

• There are two types of error that need to be considered:

• syntax error
  
• logic error

Errors & Bugs

What is a bug?

1. An error in an algorithm
2. An error in a program
3. A way of stopping a program that is running
4. An insect in the computer

• Syntax is the spelling and grammar of a programming language

• Programming languages have rules for spelling, punctuation and grammar, just like the English language. 

• In programming, a syntax error occurs when:

1. There is a spelling mistake
   
2. There is a grammatical mistake
   

• Syntax errors will cause a program to crash or not run at all. 

Syntax Errors

1. Spelling Mistake
2. Grammar Mistake

1. Spelling Mistake
2. Grammar Mistake

1. Spelling Mistake
2. Grammar Mistake

Logic Errors

• Logic errors occur when there is a fault in the logic or structure of the program.
  

• Logic errors do not usually cause a program to crash. However, logic errors can cause a program to produce unexpected results.

• More than one type of logic error can exist. Parts of the program may:
  

1. Be in the wrong sequence
2. Have the wrong Boolean expression
3. Be missing altogether

• Any one or more of these errors may exist in a program, and each will cause the program to behave unexpectedly.

Turn and talk

What is the difference between syntax errors and logic errors?

In pairs recreate this broken Christmas chatbot code, fix the errors until it runs and works!

CLICK HERE FOR SMALL BASIC

Click here to download broken code