Correcting Algorithms
Computer Science: OCR GCSE, topic 2.1.7
Correcting Algorithms
As well as knowing what an algorithm does, it's important to be able to fix it if it all goes wrong.
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Incorrect identifiers
- A common mistake in programs is incorrect identifiers.
- Be very careful with uppercase and lowercase letters.
- Be careful with similar looking characters:
- 0 and O.
- 1 and l (lower case L).
Incorrect operators
- Look out for the difference between similar operators such as testing if a number is less than another, rather than less than or equal to the other.
Missing processes
- Sometimes a line of code has been forgotten, which can lead to issues such as infinite loops, where the code will never end.
Examples of how to Correct Algorithms
Incorrect identifiers
- In this example, there is a problem on line 1.
- Weather has initially been misspelt.
- If the program were to run, the programmer would see an error indicating that there is no variable that is named weather, because instead, it was defined before as whaether. So, the program can not see if the value of sun is stored within the weather variable.
Incorrect operators
- This code determines whether a number is odd or even.
- A number is even if it is EXACTLY divisible by 2 with NO REMAINDER.
- The error is on line 3.
- Whilst >= does include 0, it also includes the only other answer of 1.
- If this program were to be run, all numbers would be shown as even.
- To fix the code, we need to replace > with =
Test yourself on Correcting Algorithms
Which of these characters gets most commonly confused in programming?
What is the most common operator mistake?