When an externally-described WORKSTN file is processed, the IBM i system transforms data from the program to the format specified for the file and displays the data. When data is passed to the program, the data is transformed to the format used by the program.
The IBM i system provides device-control information for processing input/output operations for the device. When an input record is requested from the device, the IBM i system issues the request, and then removes device-control information from the data before passing the data to the program. In addition, the IBM i system can pass indicators to the program indicating which fields, or if any fields, in the record have been changed.
When the program requests an output operation, it passes the output record to the IBM i system. The IBM i system provides the necessary device-control information to display the record. It also adds any constant information specified for the record format when the record is displayed.
When a record is passed to a program, the fields are arranged in the order in which they are specified in the DDS. The order in which the fields are displayed is based on the display positions (line numbers and position) assigned to the fields in the DDS. The order in which the fields are specified in the DDS and the order in which they appear on the screen need not be the same.
For more information on processing WORKSTN files, see Valid WORKSTN File Operations.