HP 71B FORTH/Assembler ROM

[Garth Wilson]

(09-02-2022 09:16 AM)KimH Wrote:  The "Manual" does not have a single example "to learn from". Do you have a suggestion/source on how one can get more examples like what you did here. Is there a good paper/book/page to go look at?

This was a slight difficulty I ran into when I got into Forth in 1990, which was on the 71. KeithB linked to the excellent "Starting Forth" book above, on Forth, Inc.'s own website, a version with a few modernizations over the original but keeps the original beloved cartoons. KeithB, BTW, was the one who originally made me aware of Forth, and got me interested in looking into it. The book more or less assumed you had something to practice on, while the Forth ROM's manual assumed you were already familiar with Forth and just needed to know a few particulars about the 71's unusual implementation with 20-bit cells and 4-bit data at each address; so they were kind of left pointing at each other. I did eventually get going though.

The 71's Forth seems to be Forth-79, although I'm not intimately acquainted with all the differences between Forth-79 and Forth-83 which I later got a lot more experience on with the 6502, or the differences between Forth-79 and the earlier fig-Forth. The 71's implementation was pretty inefficient; but since it's Forth, it of course allowed me to make a lot of improvements, including speeding up existing Forth words. In the extreme case, which I think was CHR$, I was able to make it 14 times as fast, without even resorting to assembly language.

Last year, I saw an interview with Leo Brodie, the author of Starting Forth, and of the sequel, "Thinking Forth" which is almost more about programming philosophy but shows how to do all kind of unexpected things in Forth. (It has a lot of power that does not immediately meet the eye, and which even the intermediate user won't yet be aware of.) Brodie still looks a lot like his picture on the back of the paper book—just add a few years—and is still very sharp, humorous, and good-natured. He drew the cartoons for the book himself.

(09-02-2022 07:06 PM)robve Wrote:  Mistakes can hurt (more) with FORTH.

I have to disagree; but I do seem to have an RPN brain, and Forth came much more naturally to me than algebraic languages, and it's easier for me to write without mistakes in Forth.