[theamk]

x86 had 6 general-purpose working registers total. Using length + pointers would have caused a lot of extra spills.

[masklinn]

“Sure your software crashes and your machines get owned, but at least they’re not-working very fast!”

[tialaramex]

Right. This is so often the excuse for terrible designs in C and C++. It's wrong, "But it's faster". No, it's just wrong, only for correct answers does it matter whether you were faster. If just any answer was fine there's no need to write any of this software.