Is one's complement a real-world issue, or just a historical one?

Question

Another question asked about determining odd/evenness in C, and the idiomatic (x & 1) approach was correctly flagged as broken for one\'s complement-based systems, which

Answer 1

This all comes down to knowing your roots.
Yes, this is technically an old technique and I would probably do what other people suggested in that question and use the modulo (%) operator to determine odd or even. But understanding what a 1s complement (or 2s complement) is always a good thing to know. Whether or not you ever use them, your CPU is dealing with those things all of the time. So it can never hurt to understand the concept. Now, modern systems make it so you generally never have to worry about things like that so it has become a topic for Programming 101 courses in a way. But you have to remember that some people actually would still use this in the "real world"... for example, contrary to popular belief there are people who still use assembly! Not many, but until CPUs can understand raw C# and Java, someone is going to still have to understand this stuff.

And heck, you never know when you might find your self doing something where you actually need to perform binary math and that 1s complement could come in handy.