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colorForth and the Art of
the Impossible
Howerd Oakford,
Inventio Software Ltd, 19 Oct 2001
www.inventio.co.uk
"I choose
a block of marble and chop off whatever I don't need" Auguste Rodin ( when
asked how he managed to make his remarkable statues ).
The direction
of computer science in the early twenty-first century is the same as the
culture which is creating it – global, standardised uniformity. How refreshing
to find a new programming environment which bucks the trend.
ColorForth
Chuck Moore
described his ColorForth as "brutally simple". Using it has been
compared to "programming an alien computer". It is gloriously
non-standard.
·
ColorForth uses only 27 of the 102
or more keys available, and the letters are not the ones printed on the
keyboard. The Enter key is not used, and the space bar is used to enter a
command.
·
The font provided as standard is the
conventional Latin alphabet, but is not in alphabetical order,
and can be modified by the Icon editor to display any pattern you like.
·
Characters are stored using Huffman
encoding, not ASCII. Yes, ASCII is not used. 'a' is 5, not 97, 'b' is 19, not
98. Definitely not ASCII...
·
The text editor stores pre-parsed Huffman
encoded strings ( one or more 32 bit values ) into
Blocks, and must Huffman decode before
displaying them.
·
One call to the BIOS to set up the
video card is all that remains of the layers of operating system which usually
cripple your PC.
So you've found a
computer with the right sort of AGP ( or PCI ) video card, and ( in my case )
dug up an old multi-function ISA card with a compatible floppy disk chip and
got colorForth to boot. What next?
The bottom right hand corner of the screen displays a table of the
functions of the 27 active keys on your keyboard. Press "e" and the
enter key, ( or "d" and the space bar as they are more commonly
known, ) to start the editor.
Something like
a Forth block appears on the screen, but without the line numbers, and in lots
of different colours, and the keyboard pattern changes to show you the new set
of functions which define the editor. "-" and "+" ( the
"M" and "/" keys ) move up and down the blocks 2 at a time (
documentation is on odd numbered blocks ).
Having viewed
the source, exit the editor ( by pressing the space
bar ), and load the Icon editor by typing "icon" . You can now edit
the font.
If you edit the
pattern for a character which is currently being displayed on the screen you
will see all occurrences of that character change. This is because there is a
display task which continuously executes the Forth code following the word
"show".
Everything you
see on the screen is being continuously updated, at 24 Hz in my case,
synchronised to the video display frame rate.
This is your
opportunity to edit all of the character set to say, the Greek or Cyrillic
alphabet, if that is what you are more comfortable with.
Type
"save" to save the system to disk, but keep
plenty of backups!
So you've learnt
how to type using only 27 keys, to edit in colour, to setup a new keypad and
actions. What next?
I visualise
this new Forth environment as an infinitely large granite table, thinly marked
out with a square grid. Each square is a Forth block. Some of the squares are
filled by little islands of coloured text - these are the programs. One square
is "home", where you start from. When you first run colorForth, this
home square is the Forth outer interpreter, something like QUIT. If you type a
Forth word's name here, you will execute it.
When you run
one of these programs, you "jump" to that square, and you then see
the world from there. Lets
jump to the editor. The keypad actions change, and a new keypad display appears
on the screen. The outer interpreter is no more, just editor functions. Now
jump to the icon editor - yet another keypad design and set of functions.
ColorForth has several innovations - circular
stacks, the splitting of the @ and ! atoms, the use of ones' complement
subtraction and other improvements which have come out of Chuck's hardware
designs.
But for me, the
big one is the way that Chuck has applied the Forth “philosophy” to the Forth
language, and created an environment which connects program context to the
human brain in a simpler way :
The keypad
display is a visual mnemonic for the program context and keypad actions. These
actions have all of the possibilities that we are used to in Forth,
but live in a world with even fewer boundaries.
The Art…
In conventional
computer languages the system is divided up into functionally different
components – editor, compiler, linker, debugger, emulator etc. An interface is
defined between each component, and often this is a file containing ASCII
characters. ColorForth has utilities to create such a file, in order to
interface to the rest of the world, but does not use
this format internally. It is easy to overlook the magnitude of this last
sentence.
What are the
advantages of discarding so much that is taken as fundamental by the rest of
the computing world? This is in fact the wrong question,
because it assumes that the decision to use or discard each and every
standard was made on the basis of its relative advantages or disadvantages,
taken separately. If you start with that mindset you
will discard colorForth at the first hurdle. It is discussing the pile of
rubble on the floor, not the work of art.
ColorForth is
the way it is because it is necessary to be that way. It has its roots in the
reality of its own environment, not in layers of artificially constructed
interfaces.
…of the
Impossible
Suppose for a
moment that a computer removed from a crashed alien craft was powered up and
its software analysed. What would it be like?
The keyboard
would be more likely to have 27 keys than 102. The QWERTY keyboard has evolved
from mechanical typewriters which needed one key for each character. If the
aliens are carbon-based life forms they probably have
relatively few digits, like us, so 27 keys would be more than enough.
The use of two
stacks and multiple small procedures ( i.e. Forth )
can be discovered by any sufficiently advanced civilisation as a good way to
write programs, likewise Huffman coding is a universal expression of data compression
using a binary tree.
ASCII is just
an Earth-bound agreement. The “operating system” approach with its manifold
API's is merely an artefact of 21st century Western business
practices.
Is it possible
that two different civilisations, separated by time and space, could discover
the same reality? Could ET have created colorForth?
Conclusion
Many people
have been using Forth to create programs which are impossible with any other
language. ColorForth is one of those programs. I like it.