FORTH & HP: where to start?

[Didier Lachieze]

From THE HP-41 TRANSLATOR PAC FOR THE HP-71 by Bill Wickes:

Quote: RELATION TO THE FORTH/ASSEMBLER ROM

The Translator Pac FORTH system is very similar to that contained in the HP 82441A Forth/Assembler ROM. At first approximation, the Translator Pac just is the FORTH/Assembler ROM, with the HP-41 vocabulary substituted for the Assembler (the KEYBOARD IS lex file is also not present in the Translator Pac). This has the drawback noted previously that both modules can not be plugged into the HP-71 simultaneously. But further, the two FORTH systems cannot share the same RAM files. This is due to the differing organizations of the system portions of the RAM files, and to the fact that the ROM-based FORTH dictionaries are different, so that the compilation addresses of the ROM words are not the same for the two systems. The FORTH/Assembler ROM’s RAM file is named FORTHRAM; the Translator Pac’s is named FTH41RAM. The different names should help programmers keep the two types of files sorted out.

Here is a brief summary of the primary differences between the two
FORTH systems:

• The Translator Pac does not contain the Assembler, the associated words ASSEMBLE, PAGESIZE, LISTING, and VARID, and the Assembler user variables.
• With the exception of the Assembler words, the Translator Pac Rom dictionary is a superset of that of the FORTH/Assembler ROM. The Translator dictionary is organized into two vocabularies: FORTH and HP41V. The former is the parent vocabulary of the latter, so that FORTH words are available when the context vocabulary is HP41V, but not vice-versa.
• The Translator Pac FORTH vocabulary is augmented by numerous HP-41 floating-point words that are not included in the FORTH/Assembler ROM.
• Translator Pac floating-point words follow the HP-41 convention that errors leave the floating-point stack intact. The FORTH/Assembler words drop the stack, update LASTX, etc., before error-checking.
• The Translator Pac HP41V vocabulary contains HP-41 words that depend on HP-41 data structures or use post-fix notation.
• The user variable area in the FTH41RAM file contains the HP-41 flags, program pointer, return stack, alpha register, size and sigma register variables, and other HP41 system variables.
• The FTH41RAM user dictionary begins with the FORTH word, but also contains the HP41V vocabulary word, and a null word used to link the various RAM and ROM dictionaries together.
• The outer interpreter loop in the Translator Pac checks an emulator-active flag following interpretation of the input buffer. If the flag is clear, the OK { n } message is displayed. If set, a vectored HP-41 display word is executed (typically, to display the X-register).
• HP-41 error messages (Alpha Data, Data Error, etc.) are added to the system error table in the Translator Pac.
• The [ATTN] key and poll check carried out during execution of semicolon and branching has been rewritten for the Translator Pac, resulting in somewhat faster FORTH execution.
  

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