You're right, not that hard to hand translate, with the table on page B-4. Human error in splicing together the photocopies.
So the missing lines are, as we figured:
50 F = N
60 N = N-1
I made little pencil marks on the tape so I can take more photocopies and splice them together and post it to Flicker, but I think this dead horse is sufficiently beaten now (until I get stuck on real work and need to divert for few minutes...)
In every Basic I've ever used the interpreter would tell you if you had an uninitialized variable. In fact, one of my favorite computer pranks was when I was at the remote end of a software demo. Two very clever guys from a different high school had created a program in Basic that allowed separate time-shared teletype sessions to chat, using shared files as storage.
OK, so they're in the other room and the program is working fine. We're sending back and forth the usual "HELLO", "HOW ARE YOU?", "FINE THANKS", and other unimaginative messages you can expect from teen-agers who did math instead of literature. I got a diabolical inspiration and sent the message "UNDEFINED VARIABLE IN LINE 1320". They panicked, and started giving commands like "LIST" and "RUN", not realizing that the program was still running perfectly. I dashed into the next room and asked "what happened?" and let them sputter a bit before confessing.
Wirth's Law: "Software is getting slower faster than hardware is getting faster."
I did take a Tic-Tac-Toe (on a cylinder or something funky) I'd written for Data Structures and it was an amazing example of Moore's Law. In 1982 each move took the computer about three hours. In 2005 the same code was running in interactive time (and I learned it was a very boring game, guaranteed win for the first mover.)
I don't recall pre-initialized variables, certainly not to 1, so I suspect there are lines missing, given there are no lines 50 or 60, and the GOTO 60.
@Chesler....you could initialise F by saying F=1 or F=N, but unless the machine defaults to initialising variables to 1 your initial program would not work. But I don't know how that machine behaved....
> "What am I doing debugging/reverse engineering this?"
Well you can see how far you have come since those early days,,,,and a bit of nostalgia is always a good thing I find.
I loved playing with GWBASIC again but I was forever trying to position the cursor with the mouse, or cut and paste....NOT! But as I remarked above, the power of that little program in 60K is awesome compared to todays's bloated code. But then would I want to go back to Wordstar or MS-Word DOS versions without WYSIWYG? I don't think so..... Then again GWBASIC appears on the screen ready to work about 0.4 second after clicking it. You never gain anything without also gaining a disadvantage.....
What am I doing debugging/reverse engineering this? Since N is set to N-1 before the loop, I'm thinking F was initialized to N, not to 1.
I remember being amazed at how quickly the answer came back (relative to 110 baud -- but a state-of-the-art TI-30 of the same vintage has noticable lag coming back with a trig value) so maybe I was trying to be clever and save a multiplication.
@Chesler....no problem, I had lots of fun with it. (If MS had not updated everything I'd still be quite happy with DOS and BASIC and Wordstar :-)
In your original program, if Nwas input as 1, it would have got 1 subtracted from it first, and you would have got an endless loop. Mine can cope with 1 but not 0 or negative Ns.
I remember being taught that unconditional jumps like GOTO 60 were a no-no, and to use DO WHILE or FOR N = x TO y instead. Good point.
I did a FORTRAN course once and put and endless loop in a program, I got presented with a 2 inch high stack of paper and a very stern talking-to from the computer centre manager when I went to collect my printout. We all have to start somewhere.....