Aims

• Know why files are used in programming code and the different modes that are used to interact with text files.

• Be able to write pseudocode that writes data to a text file and reads data from a text file.

Files

Whilst program is running, data is held inside variable/constant/array etc. all held data is lost when the program ends.

To permanently keep data it needs to be held in an external file. e.g. text file

Text files need to specify mode:

• READ - data to be read from the file.

• WRITE - data to be written to the file, new file is created & any new existing data in the file is lost.

• APPEND - data to be added to file after any existing data currently in file.

Writing To A Text File

Syntax

E.g. allow user to input their name & then add this to a text file called names.txt

DECLARE name : STRING

INPUT name

OPENFILE “names.txt” FOR APPEND

WRITEFILE “names.txt” , name

CLOSEFILE “names.txt”

Reading To A Text File

Syntax:

Variable should be STRING, when READFILE command is executed, next line of text in file is read and assigned to the variable.

E.g. Read first line from text file called test.txt

DECLARE lineOfText : STRING

OPENFILE “test.txt” FOR READ

READFILE “test.txt”, lineOfText

CLOSEFILE “test.txt”

Function EOF can be used to test whether there are any more lines to be read from a given file. Function returns true if there are no more lines to read/empty file & false otherwise

E.g. DECLARE lineOfText : STRING

OPENFILE “test.txt” FOR READ

WHILE NOT EOF (“test.txt”)

// READFILE “test.txt”, lineOfText

// OUTPUT lineOfText

CLOSEFILE “test.txt”

Example of A Level question - how to copy from one file to another