That was an enjoyable read. I, too, when I was a child sometimes thought the same thing about my C64 “magically” being able to load some game-related images with just a few lines of code that are… just somewhere inside it? A super bizarre thought, but as a child you’re still prone to a lot of magical thinking.
> and the convoluted logic "440 IF GOTO 450“
To expand a little bit on that, while some instances in the code of your book could indeed use some cleanup (line 440 is especially egregious), the code in the book was likely written for the common BASICs of home computers of the time, which only operated on line numbers and had very limited branching statements?
The BASIC you use seems to be “structured”, which was extremely unusual for home computers of the time. I just recently saw that a C64 magazine from 1984 spent at least 3 issues of the magazine on a lengthy article series that introduced the readers to the wonders of structured programming!
The severe restrictions of the IF statement made assembly-language style conditional branches (using GOTO) extremely common and necessary.
You definitely could not nest IFs (as done in your code), so if you wanted to combine IFs together, you had to jump over the ones not taken. Commodore/C64’s BASIC (effectively Microsoft BASIC) did not even have ELSE, so usually ELSE had to be implemented with a negated condition and jumping over what would be the “ELSE” branch.
C64 BASIC did however have the interesting quirk that any other statement on the same line would belong to the THEN, e.g.
10 IF A=1 THEN PRINT “FOO” : PRINT “BAR”
Would print FOO BAR if A=1, and nothing otherwise. This of course worked only so far as you could fit statements on a (limited) single BASIC line. Other BASIC dialects would consider the PRINT “BAR” to not belong to the ELSE anymore, which is syntactically cleaner, but could be less convenient depending on what else the dialect offered.
A lot of the convenience and rigor we take as granted today wasn’t there. C64 BASIC seemed especially “dirty” to me, having lots of bizarre quirks that are more the result of its implementation. (Another random instance: Every function had to have an argument, whether it was required or not, so you had to write something like “?FRE(123)” to print the amount of free memory, where the 123 did not matter at all.)