pdp-11 assembly standards

[Don North]

On 1/8/2017 9:10 PM, Brent Hilpert wrote:
> OK, what was the standard (if there was one) number-base syntax for PDP-11 assembler?
>
> Despite all the PDP-11 assembly info on web sites, this seems to be a buried bit of info.
> One assembler doc uses a prefix of "&o", another specifies octal as default and prefix of zero for decimal (opposite of the common C-derived standard . . great).
>
> Is this for example standard?:
>
> 		BIT #&o200, @#&o177564		; test 2^7 bit at address octal 177564
>
> (I'm just trying to make some written commentary consistent with common policy.)
>
>
MACRO11 Language Manual v5.5 section 6.4

All numbers are octal radix, unless the default radix is changed via the .RADIX 
N directive (N can be 2, 8, 10, or 16). N blank resets the radix to octal.

So 0100, 100 would be octal 100, decimal value 64.

Any number followed by a period (decimal point) is forced to be base 10.

So 100. would be decimal 100, octal 144.

Prefix operators ^B (binary), ^O (octal), ^D (decimal), ^X (hexadecimal) force 
the following digits/characters to the designated radix.

So ^B101000 == ^O50 == ^D40 == ^X28 all represent the same value (decimal 40.) 
irrespective of the current .RADIX N setting.