5.1.5.1 "COBOL Language Reference" IBM Library Server

5.1.5.1 File Data

File data is contained in files. (See "File Section" in topic 5.2.1.) A file is a collection of data records existing on some input-output device. A file can be considered as a group of physical records; it can also be considered as a group of logical records. The Data Division describes the relationship between physical and logical records.

A physical record is a unit of data that is treated as an entity when moved into or out of storage. The size of a physical record is determined by the particular input-output device on which it is stored. The size does not necessarily have a direct relationship to the size or content of the logical information contained in the file.

A logical record is a unit of data whose subdivisions have a logical relationship. A logical record can itself be a physical record (that is, be contained completely within one physical unit of data); several logical records can be contained within one physical record, or one logical record can extend across several physical records.

File description entries specify the physical aspects of the data (such as the size relationship between physical and logical records, the size and name(s) of the logical record(s), labeling information, and so forth).

Record description entries describe the logical records in the file, including the category and format of data within each field of the logical record, different values the data might be assigned, and so forth.

After the relationship between physical and logical records has been established, only logical records are made available to you. For this reason, a reference in this manual to "records" means logical records, unless the term "physical records" is used.

Adobe, the Adobe logo, Acrobat, the Acrobat logo, and Acrobat Reader are registered trademarks of Adobe Systems incorporated.

5.1.5.1 File Data

IBM Library Server Copyright 1989, 2005 IBM Corporation. All rights reserved.