AT&T assembly style significantly predates C++ (and C# by like two decades), and co-evolved with C. And strictly this isn't an assignment, anyway. Assignment is an abstract operation in a programming language. This is a machine instruction[1] for a physical machine, which does exactly one thing.

[1] Pause while the peanut gallery points out that in fact there are like ninety six different instructions in x86 called some variant of "MOV". Yeah, yeah, we know.