• Why not?

      I didn’t have the specific Unicode codes memorised. Those I found on Wikipedia. But the knowledge that there exist spaces of different sizes and the non-breaking space just comes out of my general interest in computers across the board.

        • I have a few alt codes memorised, but not very many. 0151 and 0150 are — and – (em and en dash) respectively 8230 is ellipsis, except for some reason that doesn’t work in all applications, including web browsers.

          255 is apparently the non-breaking space, so same as U+00A0 mentioned above. It can also be written in some websites (including here) with  . Like this.