Text files · ⁨Текстовые файлы⁩

A file keeps data after the program stops

• The 2026–2028 syllabus (section 8.3) stores data in a text file.
• You open the file, read or write one item, then close it.
• This course keeps the file in memory for the one run, so you can see the result.

DECLARE LineOfText : STRING
OPENFILE "Note.txt" FOR WRITE
WRITEFILE "Note.txt", "Hello"
CLOSEFILE "Note.txt"
OPENFILE "Note.txt" FOR READ
READFILE "Note.txt", LineOfText
CLOSEFILE "Note.txt"
OUTPUT LineOfText

READ and WRITE

• OPENFILE "name.txt" FOR READ reads what is already there.
• OPENFILE "name.txt" FOR WRITE starts a new file. Anything already in it is lost.
• READFILE puts the next item into a variable. WRITEFILE stores a value.
• CLOSEFILE when you have finished. A file is open in only one mode at a time.

DECLARE LineOfText : STRING
OPENFILE "FileA.txt" FOR WRITE
WRITEFILE "FileA.txt", "Saved"
CLOSEFILE "FileA.txt"
OPENFILE "FileA.txt" FOR READ
READFILE "FileA.txt", LineOfText
CLOSEFILE "FileA.txt"
OPENFILE "FileB.txt" FOR WRITE
WRITEFILE "FileB.txt", LineOfText
CLOSEFILE "FileB.txt"
OUTPUT LineOfText

Read every line

• EOF("List.txt") is TRUE when there is no further line to read.
• WHILE NOT EOF(...) reads the whole file. Each READFILE puts the next line into a STRING.
• Close the file when you finish. A later open can use it again.

DECLARE LineOfText : STRING
OPENFILE "List.txt" FOR WRITE
WRITEFILE "List.txt", "Red"
WRITEFILE "List.txt", "Blue"
CLOSEFILE "List.txt"
OPENFILE "List.txt" FOR READ
WHILE NOT EOF("List.txt") DO
    READFILE "List.txt", LineOfText
    OUTPUT LineOfText
ENDWHILE
CLOSEFILE "List.txt"

Watch out

• Declare the variable before you READFILE into it.
• WRITE replaces the file. Read it first if you still need the old text.

Common mistakes

• Open for READ or WRITE, then READFILE or WRITEFILE, then CLOSEFILE.
• The name of the file is a string, in double quotes.

Now you try

• Write a line, read it back, and OUTPUT it.
• Press Check answer to test it.