From mboxrd@z Thu Jan  1 00:00:00 1970
From: ron@ronnatalie.com (Ron Natalie)
Date: Wed, 21 Mar 2018 16:55:01 -0400
Subject: [TUHS] FORTRAN
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>    DEC did a BASIC compiler for RSTS and RSX

BasicPlus was about the only good thing about RSTS.    In fact, we were allowed to replace the RSTS with UNIX at JHU if we could get BASIC PLUS ported over.
Fortunately, RSTS used EMT instructions for system calls (bizarre if you read the PDP-11 Processor Handbook) where as UNIX used the expected TRAP instruction.   All we had to do was add a "nostack" system call (I think we put it in, it might have already been there) to disable UNIX's idea of how a stack should work.