What are INPUT PROCEDURE and OUTPUT PROCEDURE?

INPUT PROCEDURE- It defines the operations where input files are first opened. After opening, records are read, edited and altered. It then goes for sorting operations and finally the files are closed.
[plain]RELEASE recordname FROM inputrecord [/plain]

OUTPUT PROCEDURE- It defines the operations where output file is first opened and it receives the sorted record in output record. Then the file is written and finally closed.

[plain] RELEASE recordname FROM inputrecord[/plain]