It's not just semantics. With synchronous code, the blocking aspects are invisible in when reading code: size_t rcnt = read (fd, buf, sizeof (buf)); /* no

It's not just semantics. With synchronous code, the blocking aspects are invisible in when reading code: size_t rcnt = read (fd, buf, sizeof (buf)); /* nobody knows if we will block */ With some async code, the fact that there will be a wait and then a continuation is visible from just reading the code.