Function keys should be provided for interim command entries, i.e., for actions taken before the completion of a transaction.
Additional Information:
Function keys will aid such interim actions as DITTO, CONFIRM, and requests for PRINT, or HELP, and also interrupts such as BACKUP and CANCEL. Interim control refers to an action taken by a user while working with displayed data, e.g., while still keying data entries or changes. Function keys will aid interim control entries partly because those entries may be frequent.