Why does Objective-C use YES/NO macro convention instead of true/false?

Question

Most languages use the true/false keywords for boolean values. I found that even Smalltalk is using true/false. I know Objective-C is just borrow

Answer 1

The best way to think of this is that it's parallel evolution.

Objective-C's BOOL and YES/NO dates all the way back to early 1980s, and was likely intended to not only mimic other languages but miss C's future development. _Bool, true/false in C were only made part of the standard in 1999.

So are YES and NO historical? Yes. Are they only historical? No. Just as NULL is not the result of 3-3 in a pure sense (despite NULL often being defined as 0, or casually usable if it were), true is not a value for BOOL.

You would not (I think) write this code:

int matches = NULL;
for (int i = 0; i

This is less obviously wrong, but it's on the same spectrum:

BOOL foundMatch = false;
for (int i = 0; i