File:  [gforth] / gforth / model
Revision 1.10: download - view: text, annotated - select for diffs
Mon Dec 31 19:02:24 2007 UTC (9 years, 11 months ago) by anton
Branches: MAIN
CVS tags: v0-7-0, HEAD
updated copyright year after changing license notice

This file describes the implementation model of Gforth. The things
described herein are valid in all implementations of Gforth.
!! needs updating

\ Copyright (C) 1995,2000,2003,2007 Free Software Foundation, Inc.

\ This file is part of Gforth.

\ Gforth is free software; you can redistribute it and/or
\ modify it under the terms of the GNU General Public License
\ as published by the Free Software Foundation, either version 3
\ of the License, or (at your option) any later version.

\ This program is distributed in the hope that it will be useful,
\ but WITHOUT ANY WARRANTY; without even the implied warranty of
\ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
\ GNU General Public License for more details.

\ You should have received a copy of the GNU General Public License
\ along with this program. If not, see http://www.gnu.org/licenses/.

The instruction pointer (ip) is post-incremented.

Branches are relative:
	branch
offset:	target - offset
	...
target:	...

The top-of return stack is in memory

The top of data stack need not be in memory. Other data stack items
are in memory.

The stacks grow downward

flags are represtented by 0 and -1

The loop control parameters are the index on the top of return stack
and the limit on the second item.

Everything except the virtual machine registers (ip, sp, etc.) is
addressable.

The return address on the return stack occupies one cell.

There is a floating point stack
The floating point numbers are the same as C's double numbers

The error returns of the file word set are FALSE or TRUE. (or should
we use errno? Does this work with stdio functions?)

No assumptions can be made about the order of fetching the xt of the
next word wrt the other operations in a forth word. This makes a
difference only if you want to execute code lying on the stack or if
you store into the very next word that is executed.

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