Annotation of gforth/model, revision 1.1

1.1     ! anton       1: $Id: model,v 1.3 1992/09/11 12:13:54 anton Exp $
        !             2: Copyright 1992 by the ANSI figForth Development Group
        !             3: 
        !             4: This file describes the implementation model of ANSI figForth. The things
        !             5: described herein are valid in all implementations of ANSI figForth.
        !             6: 
        !             7: The instruction pointer (ip) is post-incremented.
        !             8: 
        !             9: Branches are relative:
        !            10:        branch
        !            11: offset:        target - offset
        !            12:        ...
        !            13: target:        ...
        !            14: 
        !            15: The top-of return stack is in memory
        !            16: 
        !            17: The top of data stack need not be in memory. Other data stack items
        !            18: are in memory.
        !            19: 
        !            20: The stacks grow downward
        !            21: 
        !            22: flags are represtented by 0 and -1
        !            23: 
        !            24: The loop control parameters are the index on the top of return stack
        !            25: and the limit on the second item.
        !            26: 
        !            27: Everything except the virtual machine registers (ip, sp, etc.) is
        !            28: addressable.
        !            29: 
        !            30: The return address on the return stack occupies one cell.
        !            31: 
        !            32: There is a floating point stack
        !            33: The floating point numbers are the same as C's double numbers
        !            34: 
        !            35: The error returns of the file word set are FALSE or TRUE. (or should
        !            36: we use errno? Does this work with stdio functions?)
        !            37: 
        !            38: No assumptions can be made about the order of fetching the xt of the
        !            39: next word wrt the other operations in a forth word. This makes a
        !            40: difference only if you want to execute code lying on the stack or if
        !            41: you store into the very next word that is executed.

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