This script defines break utilities and is included in the J standard library. Definitions are loaded into the z locale.
setbreak 'default' is done by the profile.
setbreak creates file
~break/Pid.Class and writes 0 to the first byte.
Pid is the process id and Class is normally 'default'.
setbreak calls 9!:47 with this file.
9!:47 maps the first byte of file, and JE tests this byte for break requests.
Another task writes 1 or 2 to the file for attention/break.
9!:46 returns the filename.
break y sets break for JEs with class y.
JEs with the same class all get the break. A non-default class protects JE from the default break.
A new setbreak replaces the old.
|break||v||break J execution|