The way I picture it; see the caps set (10) as the default. From there you can shift to the lower-case (11) set, figure (01) set, or control (00) set. But the

The way I picture it; see the caps set (10) as the default. From there you can shift to the lower-case (11) set, figure (01) set, or control (00) set. But then there's no such thing as CTRL+; - you're switching to two different sets (figures and control) simultaneously. Your keyboard and OS may (should) be able express that, but ascii can't.