AT&T 6300 Programmer's Manual page 667

Converting Programs
FILE I/O
In GWBASIC, the reading and writing of
information to and from a disk file is achieved
by opening the file to associate it with a
particular file number, then selecting
particular I/O statements that specify that file
number. In some other BASICs, the I/O to
disk is somewhat different. Refer to Chapter 4,
"Disk File Handling," and to the Reference
section under the OPEN statement, for fuller
descriptions.
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