ICL 1900 Series George 3 Operating System Commands

MODE (MO)

Function

Sets the mode of operation of the specified (switchable) deck, or informs GEORGE that the mode has been switched on a deck that is only switchable by the operator.

Format

  1. NO USER context:
        MODE unit number,mode,T
  2. USER context:
        MODE unit number,mode

unit number is the geographical number of the tape unit in question.
mode is the character M followed by the setting required, constructed additively as follows:

Note that short gap is not allowed with 800 bpi density.
T is optional; if included it indicates that the change is temporary and the previous value will be reverted to as soon as the deck is released.
The parameters may occur in any order.

Forbidden contexts

REMOTE

Execution

  1. NO USER context

    Assuming that the tape deck is currently unloaded and switchable the deck is switched and the appropriate records are updated (that is the current and permanent settings or only the former depending on whether or not the change is temporary). If a tape is currently on the deck, its header will be re-read in the new mode, after switching. If the unit number is omitted, the change will apply to all decks which do not contain tapes.
    If the deck is only switchable by the operator, the settings will be updated and the header re-read if a tape is loaded.
    In all cases, if the tape is in use, the command will fail.

  2. USER context

    Provided that the deck is online to the user, the mode will be switched (if switchable). The change will always be treated as temporary.

Examples

MODE 32,M36,T This will temporarily change deck 32 to odd parity, long gap and 800 bpi.
MODE M36 This will change all free switchable decks to odd parity, long gap and 800 bpi. In this example any otherwise applicable deck that does not have 800 bpi will be set to 556 bpi.
MODE *MT1,M32 This will temporarily set the deck to even parity, long gap and 800 bpi

Error Messages

UNIT z IS ALREADY ALLOCATED
UNIT z IS WRONGED
NOT ALLOWED TO USE UNIT z
UNIT z NOT ON THIS INSTALLATION
MODE MISSING
z IS NOT A VALID NUMBER FORMAT
UNIT z IS NOT SWITCHABLE
UNIT z HAS FAILED TO SWITCH
z IS NOT AN ONLINE MAGNETIC TAPE
z IS NOT A VALID MODE