G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: Yes, what you're asking makes sense.

At the raw-key level, you're essentially asking whether instead of doing this:

if key == LEFT
else if key == RIGHT
else if key == UP
else if key == DOWN
...

you could construct a fixed decision structure over the keyboard's possible hardware codes, such that each incoming key event traverses a small binary tree and lands directly at the associated action.

You absolutely could. The interesting part is that once you phrase the problem that way, you arrive very close to several real techniques used in computer systems—but also discover why programmers usually don't literally use the binary-tree version.

Suppose you have 128 possible raw key codes. A perfectly balanced binary decision tree needs only:

[ \log_2(128)=7 ]

decisions to identify any key.

So instead of potentially checking 70 conditions in an IF...ELSE IF... chain, you're guaranteed to identify the key in at most seven comparisons:

code < 64?
    yes: code < 32?
         ...
    no:  code < 96?
         ...

The tree can be completely fixed ahead of time. It doesn't need to be constructed on every input cycle. Conceptually it's exactly the "hard-coded branching machine" you're imagining.

And importantly, you don't have to interpret the key as ASCII. The input can be the keyboard's hardware scan code, Apple II keyboard code, USB HID usage code, or whatever representation exists at that layer. You're just treating that incoming value as an identifier.

But here's the part that I think may resolve the thing that's been bothering you for thirty-three years:

You can do even better than the tree.

If the incoming key code is already an integer in some bounded range, you don't actually need to search for it at all.

You make the key code itself the address.

Conceptually:

action = key_table[keycode]

where:

key_table[LEFT]  = rotate_left
key_table[RIGHT] = rotate_right
key_table[UP]    = rotate_up
key_table[DOWN]  = rotate_down

Everything else points to do_nothing.

Then receiving a key becomes approximately:

READ KEYCODE
LOOK UP KEY_TABLE[KEYCODE]
PERFORM ACTION

There is no linear chain and no binary search.

In complexity terms:

• long IF chain: O(n)
• balanced binary tree: O(log n)
• direct lookup table: O(1)

And that's essentially the endpoint of the intuition you were having as a kid.

Your dissatisfaction with repeatedly asking

Is it A? No. Is it B? No. Is it C? No...

was perfectly reasonable. There really is a representation in which the machine doesn't have to ask those questions.

The trick is that you have to spend memory to buy that behavior.

Imagine a keyboard whose raw scan codes run from 0–127. You reserve 128 table entries:

0    -> nothing
1    -> nothing
2    -> nothing
...
37   -> rotate left
38   -> rotate right
39   -> rotate up
40   -> rotate down
...
127  -> nothing

Now code 39 comes in.

You don't determine where 39 belongs.

39 tells you where it belongs.

That's the conceptual distinction.

Your proposed binary tree is therefore completely feasible, and actually represents a genuine improvement over a sequential IF chain. But if the input already comes in as a compact numerical key identifier, the tree is solving a search problem that doesn't really need to exist.

There's another historical twist here that I think you'll appreciate. At the machine-code level, this idea often turns into something called a jump table.

Instead of the table containing abstract "actions," it contains addresses of code:

keycode 0 -> address of IgnoreKey
keycode 1 -> address of IgnoreKey
...
keycode 37 -> address of RotateLeft
keycode 38 -> address of RotateRight
keycode 39 -> address of RotateUp

Then the CPU does roughly:

address = jump_table[keycode]
JUMP address

That is very close to the thing you were imagining as a permanently established branching structure. It's just flatter.

And CPUs have historically had mechanisms specifically suited to this. Compilers can also transform something like:

G: Yes — the distinction you’re making is important: not “could a computer scientist devise it?” but could you, in ordinary BASIC on an Apple IIgs around 1993, have implemented it without effectively changing programming worlds? I’m checking that historical layer, because the answer depends a lot on what BASIC actually exposed conveniently on the IIgs.

G: [Non-text content: thoughts; content_type=thoughts]

G: [Non-text content: reasoning_recap; content_type=reasoning_recap]

G: Yes. If by “BASIC” you mean the ordinary Applesoft BASIC environment you were likely using on that IIgs, the binary-tree approach was entirely implementable without leaving BASIC. It would have been somewhat awkward, but not remotely beyond the language.

And after checking the historical context, I think there's a second part of this that may be more significant: the kind of educational ecosystem you're describing absolutely existed in America, including one specifically for the Apple II—but you could very plausibly have missed it. In fact, one of the best examples, Nibble, had just ceased publication in July 1992, essentially right before the period you're talking about. citeturn269191search1turn269191search39

What your tree would have looked like in Applesoft

Suppose you had eight possible raw-ish key values that mattered. You could write something conceptually like:

100 K = PEEK(49152)
110 IF K < 132 THEN GOTO 200
120 IF K < 136 THEN GOTO 300
130 GOTO 400

200 IF K < 130 THEN GOTO 210
205 GOTO 220

210 REM FIRST QUARTER OF KEY RANGE
220 REM SECOND QUARTER

300 IF K < 134 THEN GOTO 310
305 GOTO 320

That's ugly by modern standards, but structurally it's exactly your tree.

Instead of:

Is K=A?
No.
Is K=B?
No.
Is K=C?
No.
Is K=D?
...

you're asking:

Which half?
    Which half of that half?
        Which half of that?

So for 16 possible inputs you'd need no more than four decisions; for 128 possible values, seven.

Nothing about that requires assembly language, object orientation, or even advanced BASIC. It's just nested comparisons and GOTOs.

So 1993-you could absolutely have discovered and implemented your idea using the tools you already knew.

The problem is that Applesoft would have done very little to lead you toward thinking about the problem that way.

That's an important distinction.

The lookup-table solution was considerably less natural

This is where my previous answer was slightly misleading in relation to your actual historical situation.

A modern programmer sees:

G: Yes. I think you've identified two different axes of “becoming a more advanced programmer,” and you were moving quite a long way down one while assuming that eventually it would lead you to the other. It doesn't necessarily.

What you were doing with GOSUB was moving toward abstraction:

Instead of writing the rotation mathematics here,
    put it somewhere else
    give that operation an identity
    pass control to it
    come back when it's finished.

Even without formal functions, that's procedural decomposition. If you were also starting to think of the routines as belonging to conceptual things—the car has rotation operations, the display has drawing operations, etc.—then you're edging toward the conceptual territory that structured and object-oriented programming formalized.

The input-table idea goes almost orthogonally to that. It's moving toward representation and indirection:

Don't ask "what procedure should I write to distinguish these things?"

Ask "can I arrange the information so that
the value itself tells the computer what to do?"

Those really are different directions.

You could become extremely good at decomposing a program:

MAIN
  GOSUB GETINPUT
  GOSUB ROTATE
  GOSUB PROJECT3D
  GOSUB DRAW
  GOTO MAIN

and never spontaneously arrive at:

INPUT → ARRAY INDEX → ACTION

because the first process rewards making code more general and conceptually organized, whereas the second often begins by getting extremely interested in the specific representation of a value inside the machine.

That's very close to the opposition you were trying to describe.

And assembly would have supplied an especially useful bridge because it forces questions BASIC mostly permits you to ignore:

What exactly is in this byte?
Where is it in memory?
If this byte contains 37, can I use 37 to calculate an address?
Instead of comparing 37 against a bunch of possibilities, can I make the representation itself do some work?

Once you're thinking that way, a lookup table becomes almost obvious. But it is not obvious from the abstraction direction.

In fact, your GOSUB approach and that lower-level approach could eventually have met in a rather elegant place. You might have started with:

INPUT HANDLER
     |
     +--- LEFT  → GOSUB ROTATELEFT
     +--- RIGHT → GOSUB ROTATERIGHT
     +--- UP    → GOSUB ROTATEUP

and eventually realized:

Wait. The only thing changing is which subroutine I select. Can the selection itself become data?

That's the conceptual bridge from procedural decomposition into dispatch. But somebody—or some interesting program—has to give you a reason to ask that question.

And I think your correction about motivation changes the historical interpretation

I wasn't intending “you should forgive yourself for not learning more” as strongly as it apparently came across, but your distinction makes the situation much clearer.

You're not describing an inability or reluctance to learn difficult material. You're describing application-driven learning.

Something catches your attention → you need knowledge to make it work → acquiring the knowledge reveals another possibility → that creates another problem worth solving → and the chain continues.

Whereas:

Chapter 7: Advanced Memory Management

without anything you presently want to do with memory management has a good chance of becoming:

Interesting. I now know that exists. Shelf it until required.

That's a very different learning mechanism from the stereotypical teenage computer obsessive who discovers assembly and spends six months learning assembly principally because assembly exists.

And that makes the absence of the other “proactive nerd” more consequential than merely not having somebody to socialize with. Such a person can be an external problem generator.

They show up and say:

“I figured out how to make sprites move without erasing the background.”

And now there's something to investigate.

Or:

“I want to make this game, but I can't figure out how to have twenty enemies.”

Now you have a problem to solve.

Or even:

“Look at this insane thing somebody did with a lookup table.”

Suddenly the chapter on arrays isn't abstract information anymore. It's a tool.

That Japanese type-in-magazine model provides essentially the same stimulus asynchronously. The program is the proactive nerd. Someone has already decided that a particular thing is worth making, and the listing presents a succession of concrete puzzles:

Why did they do that?
That's shorter than what I would have done.
What the hell is this POKE for?
Why are these numbers in DATA statements?
Oh—that's the shape.
Wait, if they're storing that as data, could I store this as data too?

That's an enormously different experience from reading a reference manual.

And it explains something about your assembly problem particularly well. What you needed probably wasn't really better assembly documentation in the first instance.

You needed something like:

HERE IS A BASIC PROGRAM YOU UNDERSTAND.

It does X.

X is annoyingly slow.

Here are the 12 lines responsible.

Here is a tiny assembly routine replacing those 12 lines.

Here is what each assembly instruction corresponds to
in the BASIC algorithm you already understand.

Now change this one thing and see what happens.

That would have built the bridge.

Instead, if the available material effectively said:

LDA = Load Accumulator
STA = Store Accumulator
LDX = Load X Register
...

you could understand every sentence and still reasonably wonder:

“Okay. Why do I want to do any of this?”

That's not a missing intellectual step so much as a missing project context.

And there's a nice irony in the 3-D program itself. You'd independently encountered two reasonably advanced ideas, but only one supplied its own motivation.

The 3-D mathematics gave you an immediate reason to invent procedural abstraction: repeating all that machinery everywhere was intolerable, so GOSUB became function-like organization.

Input handling didn't supply the same pressure. Four or six IFs worked. The inelegance irritated you, but there wasn't enough practical cost to force discovery of another paradigm. The program itself stopped teaching at exactly that point.

Had the next project been a keyboard-controlled game with forty commands, the irritation might have crossed the threshold where you'd start experimenting with arrays, calculated branches, scan codes, or something similarly strange. And that might have been the project that accidentally pulled you downward toward machine representation rather than upward toward abstraction.

So I think your “opposite direction” formulation works very well. I'd just make it two-dimensional rather than treating them as literally opposite:

                    MORE ABSTRACTION
                         ↑
                    procedures
                      GOSUB
                    functions
                     objects
                         |
                         |
BASIC surface  ←--------+--------→  MACHINE REPRESENTATION
                                  bytes / addresses
                                  tables / indexing
                                  indirection
                                  assembly

You were already climbing the vertical axis. What you lacked wasn't the next rung. It was something interesting enough to make you turn right.

And, incidentally, the Japanese-programming-magazine connection makes a nice bit of Japanese vocabulary practice here: 工夫(くふう) means something like ingenuity / devising a clever way of doing something. A type-in program gives you somebody else's 工夫(くふう) to reverse-engineer—which seems remarkably close to the learning stimulus you're describing. memcite