Files flashcards

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What is a text file?

A type of file that stores data as a sequence of characters, organised into lines. It can be opened and read by a human using a simple text editor.

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What is a 'record' in the context of a file?

A collection of related data items, often stored on a single line in a text file. For example, a student's ID, name, and grade could form one record.

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What is a 'field' in the context of a file?

A single data item within a record. For example, in the record '123,John Smith,A', the name 'John Smith' is a field.

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What is a 'file handle'?

A reference or pointer to a file that is returned when you open it. In Cambridge pseudocode, the filename itself is used as the handle (e.g., `READFILE "MyData.txt", ...`).

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What does opening a file in `READ` mode do?

It opens an existing file and allows the program to read data from it, starting from the beginning. You cannot write to a file in READ mode.

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What does opening a file in `WRITE` mode do?

It creates a new, empty file with the given name. If a file with that name already exists, its contents are permanently deleted and overwritten.

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What does opening a file in `APPEND` mode do?

It opens an existing file and allows the program to add new data to the very end of it. If the file does not exist, it is created.

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What is the `EOF()` function used for?

`EOF(<filename>)` stands for End-Of-File. It is a boolean function that returns TRUE when the program has attempted to read past the last piece of data in a file. It's used to control loops for reading files.

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What is a common mistake when using `WRITE` mode?

Accidentally using `WRITE` mode when you meant to use `APPEND`. This will erase all existing data in the file without warning.

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Why is `CLOSEFILE` essential, especially after writing?

Data written to a file may be held in a temporary buffer in memory. `CLOSEFILE` ensures this buffer is flushed (written) to the disk, saving the changes permanently and releasing the file.