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2. AP1: S-task
• The controlling task sends a sign-off command, which (with the normal
prefix) is:
shû((4Ò0)@ Ìav),')off'
• The controlling task ceases to share the controlling variable by explicitly
retracting it, expunging it, clearing the workspace in which it exists, etc.,
without first notifying AP1 that the S-task is to remain active without a
controlling variable (see “Freestanding S-task,” in this chapter).
• An external command terminates it. This might be the UNIX command
kill or the APL system function Ìbounce.
Prefix Codes
Each character vector sent to or received from AP1 must begin with a prefix.
Sending Prefix Codes
Each time the controlling task sets the variable it shares with AP1, the value it
sets must be a character vector representing one line of input. The line need not
include a trailing newline or carriage return character.
There are five possible prefix codes. One of these, the code for APL input,
precedes any line sent to the session manager or the APL interpreter, including
system commands, lines entered for immediate execution, lines in response to Ìor ì-input, lines sent in response to Ìarbin, and lines sent to the Ç-editor. The
other four codes stand alone. If you send one of the other codes as part of a
longer line, the balance of the line is ignored. The five prefix codes are as follows:
(0 0 0 0 @Ìav),text
APL input.
0 0 1 0 @Ìav
Not meaningful in SHARP APL for UNIX. In SHARP
APL for MVS, this is a request for accounting
information, and the values returned are those in
3ÙÌai. In the UNIX version, the values returned are
3Ò¢1.
0 0 2 0 @Ìav
Interrupt signal.
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