File:  [gforth] / gforth / model
Revision 1.5: download - view: text, annotated - select for diffs
Tue Nov 7 18:06:55 1995 UTC (23 years, 11 months ago) by anton
Branches: MAIN
CVS tags: v0-4-0, v0-3-0, v0-2-1, v0-2-0, gforth-0_1beta, HEAD
added copyright headers
changes to loadfilename & co. to make savesystem transparent to
 assertions and ~~

    1: This file describes the implementation model of Gforth. The things
    2: described herein are valid in all implementations of Gforth.
    3: !! needs updating
    4: 
    5: \ Copyright (C) 1995 Free Software Foundation, Inc.
    6: 
    7: \ This file is part of Gforth.
    8: 
    9: \ Gforth is free software; you can redistribute it and/or
   10: \ modify it under the terms of the GNU General Public License
   11: \ as published by the Free Software Foundation; either version 2
   12: \ of the License, or (at your option) any later version.
   13: 
   14: \ This program is distributed in the hope that it will be useful,
   15: \ but WITHOUT ANY WARRANTY; without even the implied warranty of
   16: \ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   17: \ GNU General Public License for more details.
   18: 
   19: \ You should have received a copy of the GNU General Public License
   20: \ along with this program; if not, write to the Free Software
   21: \ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   22: 
   23: The instruction pointer (ip) is post-incremented.
   24: 
   25: Branches are relative:
   26: 	branch
   27: offset:	target - offset
   28: 	...
   29: target:	...
   30: 
   31: The top-of return stack is in memory
   32: 
   33: The top of data stack need not be in memory. Other data stack items
   34: are in memory.
   35: 
   36: The stacks grow downward
   37: 
   38: flags are represtented by 0 and -1
   39: 
   40: The loop control parameters are the index on the top of return stack
   41: and the limit on the second item.
   42: 
   43: Everything except the virtual machine registers (ip, sp, etc.) is
   44: addressable.
   45: 
   46: The return address on the return stack occupies one cell.
   47: 
   48: There is a floating point stack
   49: The floating point numbers are the same as C's double numbers
   50: 
   51: The error returns of the file word set are FALSE or TRUE. (or should
   52: we use errno? Does this work with stdio functions?)
   53: 
   54: No assumptions can be made about the order of fetching the xt of the
   55: next word wrt the other operations in a forth word. This makes a
   56: difference only if you want to execute code lying on the stack or if
   57: you store into the very next word that is executed.

FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>