pdp-11 assembly standards
pete at dunnington.plus.com
Wed Jan 11 09:01:59 CST 2017
On 11/01/2017 14:07, Noel Chiappa wrote:
> Although I note the documentation says "any valid value recognised by BBC
> BASIC" - does BBC basic use the leading '%' notation for constants?
Sort of. BBC BASIC uses the prefix '&' to specify hexadecimal numbers,
so &FFFE is the exact equivalent of 0xFFFE in C. Similarly, BASIC IV
and later (IIRC) use '%' to represent binary, thus %11111110 is the
exact equivalent of 0xFE in C. Anything without a prefix is decimal.
The use of "%o" for an octal constant is specific to Jonathan's PDP-11
cross-assembler, though, and isn't part of BBC BASIC.
There are additional prefixes in BBC BASIC, but used for indirection
rather than base notations. There are also other uses for '%' as a
suffix, to denote special integer variables with single-character names
which have fixed size and location (eg A%, B%, and @% which is used for
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