6.1.8.8 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. Permissible statements for each type of file organization are shown in Table 45 in topic 6.2.26.3 and Table 46 in topic 6.2.26.3.
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.
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