Input-Output Statements
COBOL input-output statements transfer data to and from files stored on external media, and also control low-volume data that is obtained from or sent to an input/output device.
In COBOL, the unit of file data made available to the program is a record, and you need only be concerned with such records. Provision is automatically made for such operations as the movement of data into buffers and/or internal storage, validity checking, error correction (where feasible), blocking and deblocking, and volume switching procedures.
The description of the file in the Environment Division and Data Division governs which input-output statements are allowed in the Procedure Division.
See Appendix F. File Structure Support Summary and Status Key Values for a file structure support summary.
Discussions in the following section use the terms volume and reel. The term volume refers to all non-unit-record input-output devices. The term reel applies only to tape devices. Treatment of direct access devices in the sequential access mode is logically equivalent to the treatment of tape devices.