An input file is one from which a program reads information. It can contain data records, arrays, or tables, or it can be a record-address file.
An output file is a file to which information is written.
An update file is an input file whose records can be updated. Updating alters the data in one or more fields of any record contained in the file and writes that record back to the same file from which it was read. If records are to be deleted, the file must be specified as an update file.
A combined file is both an input file and an output file. When a combined file is processed, the output record contains only the data represented by the fields in the output record. This differs from an update file, where the output record contains the input record modified by the fields in the output record.
A combined file is valid for a SPECIAL or WORKSTN file. A combined file is also valid for a DISK or SEQ file if position 16 contains T (an array or table replacement file).
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