Andrew Warren wrote:
>     I guess... But as long as EQU and CBLOCK can be used in a
>     program that also uses RES, the block isn't really "allocated";
>     it's just protected from reuse by other RES directives, in the
>     same way that registers named using CBLOCK can be kept from
>     being renamed by other CBLOCK directives.

The RAM is truly allocated by the linker, and that only happens when you use
RES.  Of course there is nothing preventing you from creating a symbol that
happens to have the value of a RAM address, but that has nothing to do with
allocating the RAM.  This is the distinction between RES on one hand, and
CBLOCK and EQU on the other.  The only reason there is any confusion is
because valid RAM addresses also happen to be integer values that can have
other meanings.

For example, the assembler can't prevent you from doing something boneheaded
like:

  bkcnt  equ  h'20'    ;number of buckets left to fill

because there is no way to tell this inappropriate useage from an
appropriate one such as:

  buckets equ h'20'    ;number of buckets in each tray

And by the way, one CBLOCK statement does not prevent other CBLOCK
statements from assigning the same values to different symbols.  Each CBLOCK
merely assigns sequential values to a list of symbols.  It has absolutely
nothing to do with RAM allocation.

>     This is in contrast to what I think of as "real" allocation...
>     Which would be the sort of thing you see in high-level
>     languages, where (generally speaking) once a variable name is
>     declared/used, other variable names will never be assigned to
>     the same RAM.

But that is exactly what RES does.  It is not possible to RES the same
memory location twice.


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