GE PAC 4020 System Manual page 5

Software for the GE/PAC 4020 computer includes
the Process Assembly Language (PAL), GE/PAC
Process FORTRAN, the TASC control interpreter,
the Real-Time and Free-Time Operating Systems,
a full set of mathematical function subroutines, a
Direct Digital Control package, numerous other
specific application-oriented programs, the AID
debugging program, and miscellaneous utility
functions.
Unique features of the GE/PAC 4020 central
processor include the TIM/TOM automatic input-
output operations; Quadritect four-level core memory
protection; and the use of quasi-instructions to
encourage and make more efficient the use of
floating-point arithmetic, circular lists, inverse to
2
memory and other advanced operations. Additional
features are its flexible and powerful memory
addressing capabilities and both word-logical and
bit-logical hardware.
Process-oriented features of special value
include automatic prevention of analog scanner and
output controller multiple selections, avoiding upsets
to processes caused by computer failures; three stall
alarms covering a wide range of possible software
and hardware problems; over-temperature detection
in the cabinetry and on the bulk and working mem-
ories; and analog and contact output devices with
enough current and power capability to remove the
requirement for interposing devices or circuits.