04.01.07

The text read off it

[04.01.07]

Since the actual physical units involved need not be designated, this provides a particularly simple way of:

1. Switching the system input, output, or peripheral punch to its alternate unit;
2. Providing continuity of unit assignment between programs.

For example, the system tape updating program, (IBEDT) produces the updated system tape on SYSUT1.

The card

1                16
$SWITCH          SYSLB1, SYSUT1

will then cause operation to continue using the updated system in place of the old. Note that density specifications are not transferred in the switching process.

Tape Operation Cards

A card of the form:

1                16
$ENDREEL
$REWIND          unit.function.name
$REMOVE

requests that the specified operation be performed upon the Functional Unit unit.function.name.

The operations are:

1. $ENDFILE — Write an end of file on the tape assigned to the specified unit.function.name.
2. $REWIND — Rewind the tape assigned to the specified unit.function.name.
3. $REMOVE — Rewind and unload the tape assigned to the specified unit.function.name.

$DETACH Card

And I/O unit which for any reason is disabled may be made unavailable for any use by a card of the form:

1                16
$DETACH          unit.name

The unit named remains unavailable until referenced by a $ATTACH card or until the Nucleus is refreshed.