Question 1

What happens if I try to open a non-existent file in READ mode?

Accepted Answer

This will cause a run-time error. Your program will likely crash unless it has error handling routines (which are beyond the scope of the P2 syllabus but good to know about). In an exam, you can assume the file exists unless told otherwise.

Question 2

What is the difference between `WRITEFILE` and `APPEND`?

Accepted Answer

This is a common point of confusion. `WRITE` and `APPEND` are file *modes* set when you `OPENFILE`. `WRITEFILE` is the *command* used to write data. You use the `WRITEFILE` command whether the file was opened in `WRITE` mode or `APPEND` mode. The mode determines *where* the data is written (start of file vs. end of file).

Question 3

Can I read from and write to a file at the same time?

Accepted Answer

In Cambridge pseudocode, a file is opened in only one mode at a time (`READ`, `WRITE`, or `APPEND`). To read from a file and then write to it, you would need to open it, read it, close it, and then re-open it in a different mode to write.

Question 4

Do I need to include the file extension like `.txt` in the filename?

Accepted Answer

Yes. In pseudocode, the filename is a string literal and should exactly match the name of the file you are targeting, including its extension (e.g., `OPENFILE "MyData.txt" FOR READ`).

Files

What you need to know

Your Programme's Long-Term Memory