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PostPosted: Tue Feb 23, 2021 7:44 am 
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Posts: 357
Just for fun I wanted to see how much memory could be saved with a headerless Forth and I came up with this definition.


0 VARIABLE BSCNTR

: HDRLESS LATEST BEGIN DUP C@ 1F AND 3 + BSCNTR +! PFA LFA @ DUP 0= UNTIL DROP BSCNTR @ . ;

The +3 is for: one byte for the Name Field byte and two for the Link field address, which would not be needed as well.

Currently I could save about 2700 bytes out of 16.4 k used so far. Which is about 16.5%. Doesn't seem like a lot.
The 16.4 k is just strictly memory used by word definitions and does not included memory used by errors, buffers or the User Area.


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PostPosted: Tue Feb 23, 2021 8:56 am 
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On the automated test equipment I did at my last place of work around 30 years ago, I got a much bigger percentage; but I had a lot of longish names like PAUSE_TEST# which was a two-byte variable.

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PostPosted: Tue Feb 23, 2021 4:22 pm 
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GARTHWILSON wrote:
On the automated test equipment I did at my last place of work around 30 years ago, I got a much bigger percentage; but I had a lot of longish names like PAUSE_TEST# which was a two-byte variable.

I can see a few factors affecting the percentage.
Working on an 8-bit, 16-bit, 32-bit or 64-bit system would have various percentages saved. An 8-bit system with 32-bit support creates a lot of overhead in the main part of the Forth system, which is probably why my percentage is so low. A 16-bit system would probably show a higher percentage of space saved due to a much smaller footprint for the Forth system due to better 16-bit mnemonics.

I suppose in all actuality, one should really only take in account new words added to the Forth system since the words are more likely to be definitions rather than primitives. Which would make the percentage-saved closer among all systems.


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PostPosted: Sun Feb 05, 2023 9:47 pm 
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Joined: Fri May 05, 2017 9:27 pm
Posts: 895
IamRob wrote:
Just for fun I wanted to see how much memory could be saved with a headerless Forth and I came up with this definition.


0 VARIABLE BSCNTR

: HDRLESS LATEST BEGIN DUP C@ 1F AND 3 + BSCNTR +! PFA LFA @ DUP 0= UNTIL DROP BSCNTR @ . ;

The +3 is for: one byte for the Name Field byte and two for the Link field address, which would not be needed as well.

Currently I could save about 2700 bytes out of 16.4 k used so far. Which is about 16.5%. Doesn't seem like a lot.
The 16.4 k is just strictly memory used by word definitions and does not included memory used by errors, buffers or the User Area.


With Fleet Forth I would define this:
Code:
: HSIZE  ( -- )
   0 WITH-WORDS
   C@ $1F AND 3 + + ;

And use it like this:
Code:
ASSEMBLER HSIZE .
EDITOR HSIZE .
FORTH HSIZE .

Or like this:
Code:
ASSEMBLER HSIZE
EDITOR HSIZE +
FORTH HSIZE + .



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