CLOSE

A file must be opened for a program to gain access to it. Files may be opened for output or for input. When a file is closed, its contents are finalized on the disk and a program no longer may access it. When a program ends, any files it has opened are automatically closed

A program can explicitly close a file when it no longer needs access. Of course, the file must first be open, so there is a file number.

CLOSE filenumber

filenumber is a number 1 through 255 of an already open file.

Usually it is fine to just let the files close automatically when the program ends. But sometimes a program creates a file, writes to it, closes it, and then opens it again for input. Or a program may work with several files in sequence and must close each file before it starts working on the next.