Re: [BLACKBOX] ARRAY as CONSTANT

From: [at]} <Aubrey.McIntosh{>
Date: Wed, 13 Feb 2008 21:50:56 -0600

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On Feb 13, 2008 9:04 PM, Oleg N. Cher <allot{([at]})nowhere.xy

> BlackBox compiler saves array data one step:
> in machine code, and two step - in memory, when code runned.
> The uneffective use of memory. (It's not good for embedded
> development.)
>

Thanks Oleg,

I have done a lot of assembly programming. There, I can usually
assign a 'group' and the linker will put the same group together in
memory even if it is from different assembly subprograms. So I could
define a group named 'parts' and enter hard coded data
.group part
  db 'screw', 'bin 5', 7
  db 'nut', 'bin 6', 12

The C environment usually restricts this choice of groups to a
standard set of choices, with names such as bss, text. I'm not really
fluent on those choices and their meanings.

I can envision a system where I put data into the ram area and use it
from there. The loader does the work of reading the file and
assigning memory, and I just access it where I expect it to be. The
assembly module might have some descriptive name such as InitDB.asm

When I do embedded programming on a PIC, this fails. The part is a
Harvard architecture. RAM is not defined at power up, and the program
lives in ROM. So, the practice of executing statements from ROM code
works across power cycles with no loader present. This works with the
standard Oberon language with no dross.

Oberon was very aggressive about efficiency, and BlackBox carries this
tradition. In BlackBox, when you execute a command a second time, the
loader is not called. The program is already loaded, why do it twice?
 But, you will still want to have variables correctly initialized.
The choices seem to be to have a routine, typically "Init" that
executes only the data initialization statements. If they do it from
a file, the file has to be online. This is a problem if, say, a
supervisor has taken his memory stick and gone for coffee. If they do
it in the program, it is just there.

So, yes, it is fairly tedious to type all these statements. I
strongly suspect that most of us have little macros that take rows of
values and produce the call to InitHelper. But I am convinced that
the system is well designed.

What I don't know, however, is how Delpi deals with this issue. Do
they do the load trick of loading RAM space once?
The example using a CONST string happens to be one where the Oberon (&
BB?) compilers do put values into permanent place and internally pass
the address around, so duplicate copying is not done.

I suppose at the language design level this is a request for CONST
structures. e.g., CONST a =(record type) 'this', 'that', 42 END;
Hmm. Chris?

-- 
-- 
Aubrey McIntosh, Ph.D.
1502 Devon Circle
Austin TX 78723-1814
http://home.grandecom.net/~amcintosh/aubrey/Search/
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Received on Thu Feb 14 2008 - 04:50:56 UTC