🚀 go-pugleaf

In article <EGDORF.89Jul21195924@zaphod.lanl.gov> egdorf@zaphod.lanl.gov (Skip Egdorf) writes:
>	   - The family of computers which the DEC 20 was based didn't
>	   originally use a stack.  There are a bunch of instructions
>	   which allow subroutine calls to occure with linked lists
>	   instead of stacks.
>
>I believe that even the PDP-6 had stacks built in from the beginning.
>From the same paper as above: (discussing original design issues)

The 10, which was based on the 6, had stack operators that worked
on regular registers. For example, PUSHJ (Push and Jump) would push
the PC using the specified register as a stack pointer, and then
jump to the effective address. POPJ would reverse that operation. The
pair provided a subroutine call mechanism. You could push arguments
onto the stack with PUSH and POP operators, although most assembly
language hackers would just use a few of the general registers
to hold arguments.

We found one difference between the KL and KI 10 when we discovered
some old code written by a long gone hacker that failed on the KL.
It did a POP P,P (pop a value off of the stack controlled by register
P and load register P with it). In one CPU version, P would be decremented
before the operation, while in the other, it would be decremented
afterwards.

I found the ability to define multiple stacks to be very handy.
A FORTH interpreter can be written in that instruction set that
is very efficient. Also, I once wrote a binary tree balancing routine
that used a pair of recursive co-routines. It took about 30
instructions for both routines. Try that with today's architectures! 
-- 
John Moore (NJ7E)           mcdphx!anasaz!john asuvax!anasaz!john
(602) 861-7607 (day or eve) long palladium, short petroleum
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The 2nd amendment is about military weapons, NOT JUST hunting weapons!