File Data
A file is a collection of data records existing on some input-output device. (See File Section.) A file can be considered to be a group of physical records; it can also be considered to be a group of 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 may itself be a physical record (that is, be contained completely within one physical unit of data); several logical records may be contained within one physical record, or one logical record may 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).)
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.
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.