On 02 Apr 2025 16:45:38 GMT, Aharon Robbins wrote:
Octal was used heavily on the PDP-11, if you used the assembler.
All DEC’s systems used octal heavily, prior to the VAX. That’s when they started using hex.
All the DEC machines prior to the PDP-11 had word lengths that were multiples of 3 (12, 18, 36), so octal worked nicely. Even though the
PDP-11 was a 16-bit machine, fields in its instruction format were still designed to line up with octal digits.
On 2025-04-04, Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
On 02 Apr 2025 16:45:38 GMT, Aharon Robbins wrote:
Octal was used heavily on the PDP-11, if you used the assembler.
All DEC’s systems used octal heavily, prior to the VAX. That’s when they
started using hex.
All the DEC machines prior to the PDP-11 had word lengths that were
multiples of 3 (12, 18, 36), so octal worked nicely. Even though the
PDP-11 was a 16-bit machine, fields in its instruction format were still
designed to line up with octal digits.
Why? "octal" means base eight ( as 'ocho' in Spanish, same Latin root).
forth>3 8 lcm .
24
Not very fitting for a 36 bit machine except for opcodes.
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