DISPLAY statement causes data to be transferred to hardware or software of the operating environment.
DISPLAY comes in two forms,
UPON device or for display of
SCREEN data. Environment variables can also be set with
DISPLAY UPON in some implementations of COBOL, along with other extensions for data transfer of graphics or other device specific needs.
DISPLAY "An error occurred with " tracked-resource UPON SYSERR DISPLAY A, B, C UPON CONSOLE DISPLAY group-data UPON user-device ON EXCEPTION WRITE device-exception-notice NOT ON EXCEPTION WRITE device-usage-log END-DISPLAY
UPON CONSOLE is a default, rarely written. Messages with DISPLAY are one way of debugging COBOL code, but many COBOL programs are transactional in nature, and might not ever interact with a human operator once a job is submitted.