interesting Univac ad from 1956

[Les Bell]

(06-06-2014 03:24 AM)rprosperi Wrote:  Yes, pretty sure the PDP-8 was an octal-based machine; the PDP-11 I got to use in college was as well, IIRC, as were Data General machines (Nova, Eclipse?).

I think the Vax was the DEC machine that ushered in use of Hex, but this is all rather fuzzy; in fact it's a bit like trying to recall a dream - the harder I try to recall details, the furthur away they seem to be sliding...

The PDP-8 was a 12-bit machine, which lent itself to octal, since a word was expressed as 4 octal digits. I'm not sure about the DG machines - I used to have some Nova documentation around here somewhere, but I think it's long gone.

The Intel 8080, despite being 8-bit, was another machine that lent itself to octal; for example, a MOV instruction was always 1xy where x and y specified the destination and source locations, respectively, from this list:

B = 0
C = 1
D = 2
E = 3
H = 4
L = 5
M = 6
A = 7

It didn't take long before one could assemble 8080 machine code in one's head, although I've forgotten it all in the years since.