Compatible fortran, A. Colin Day. Cambridge University Press, 1979. No. of pages: 107. Price: £5.95
DAVID W. BARRON · Software Practice and Experience · 1980
ported by the hardware and are little used.I removed the input/output procedures from the kernel and made it possible to program peripheral devices in Concurrent Pascal, using the ideas of Heimbigner.' Finally, I simplified scheduling by using a round-robin scheduler and by letting each process run until it either terminates or delays itself.In addition, process switching takes place whenever a process has performed one hundred conditional jumps.This reduces the time to schedule processes by an order of magnitude.By these simplifications the kernel and interpreter were reduced from 4 K words to 1.5 K words (compared to the 2.6 K words of Mattsson).Since the standard operating system for the PDP-11/45, Solo: requires 39 K words of storage to compile programs, I had to write a smaller operating system that would fit in 28 K words.This operating system was developed using Solo on the PDP-11/45.It supports the execution of the Concurrent and Sequential Pascal compilers.T h e compilation speed using dual floppy disks is 3 lines per second (compared to the 5-8 lines per second of Mattsson).T h e development of the kernel, interpreter, and new operating system required an estimated two months of full-time work.The result is a system with none of the linkage problems inherent in using two slightly incompatible versions of Pascal together.My approach was made possible by the availability of a PDP-11/45, with which an initial operating system for the LSI-11 could be developed.T h e LSI-11 operating system has been used at the University of Southern California since the spring of 1979.I t is not available for distribution.