Rich kids are into COBOL

Jon Elson elson at
Sat Feb 28 23:14:23 CST 2015

On 02/28/2015 04:59 AM, Johnny Billquist wrote:
> Not that Unix was ever written in B anyway, but I believe 
> that B did
>>> exist for the PDP-7.
I looked up the instruction set of the PDP-7, ghastly little 
machine, basically
a PDP-8 extended to 18 bits.  Stored the return address in 
the first word
of the subroutine, just one accumulator, conditionals were 
done with
a skip instruction, so you did this skip / jump structure 
for conditional
branches, unless the conditional code was only one 
instruction.  All the
stuff I disliked on the PDP-8.  One oddity was there was a 
13-bit address
field in the instruction, but it was possible to have more 
than 8K words
of memory on the machine.  Another oddity is there were both
ones-complement and twos-complement add instructions.  I guess
the designer just couldn't decide which arithmetic 
representation to use?


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