405 exec's

[utzoo!duke!mhtsa!ucbvax!DYER at HARV-10]

405 exec's have been around a while at Harvard, but only recently
have been anything more than a curiosity.  The maintainer of PPL,
a large interpretive teaching language running on our 11/70's, finally
ran out of I-space to implement a number of new features.  He used
405 exec's to implement little-used functions, exec'ing back to the
main 411 when they were finished.

Getting the Harvard MACRO-11 LINKR to produce such a file was a bit
of a mess.  Basically, one had to hand-assign the needed addresses
(based on the 411 file) and adb a 405 in the front.  Usually, several
"nm ... vi ... macro ... linkr" iterations were necessary.  However,
because these functions looked at only a small part of the available
data space, the job wasn't too laborious.  So it works, if you take the
time.

Steve