8086-8088 V10 - Forth Interest Group

Fig-Forth 8086/88 Version 1.0 Notes Page 1
Fig-Forth for the 8086/88
Version 1.0
Thomas Newman
This document will briefly describe Forth-86 and how it differs
from the Fig model. It is assumed that the reader is familiar
with the 8086/88 CPU and Fig Forth's installation manual.
This version of 8086 Forth was derived from 8080 Fig Forth
(version 1.1). The extra registers and extended addressing modes
of the 8086 were used to optimize the code portion of Forth-86
(refer to the source listing for 8086 register usage).
IMPLEMENTATION
--------------
Forth was implemented and tested on an 8088 CPU running Digital
Research's CP/M-86 (version 1.0).
All console, printer and disk drivers call tneir res?ected
routines in the "BIOS" through the "BDOS" function #50. These
calls are all located in a common program area and can be easily
modified to call your own 1/0 routines (if your're not using
CP/M) .
The following are notes about loading and executing Forth:
o The source program was assembled using CP/M's ASM86. The
mnemonics should be compatible with Intel's assembler
(except for the far CALLS and JMPs which are not used in
this version of forth).
o The forth program can be loaded into any free portion of
memory that is large enough to hold the forth kernel,
dictionary and buffers (from "ORIG" thru "EM").
o The program is executed at the offset address 10B hex with
the Code Segment (CS) equal to the base address (this is the
way CP/M executes "CND" type files).
o The "COLD" entry routine in forth will set all other segment
registers to the value of the CS register. This version of
forth assumes all data, code and stack offset addresses are