screen^aなどを実行するとき

人間のスクリーン:

   ├─────────────────┼─────────────────┼─────────────────────┤
   │C-a a            │ (meta)          │ Send  the   command │
   │                 │                 │ character  (C-a) to │
   │                 │                 │ window. See  escape │
   │                 │                 │ command.            │
   ├─────────────────┼─────────────────┼─────────────────────┤

または：

   -e xy
        specifies the command character to be x and the character generat‐
        ing a literal command character to y (when typed after the command
        character).   The default is "C-a" and `a', which can be specified
        as "-e^Aa".  When creating a screen session, this option sets  the
        default  command character. In a multiuser session all users added
        will start off with this command character. But when attaching  to
        an  already  running session, this option changes only the command
        character of the attaching user.  This option is equivalent to ei‐
        ther the commands "defescape" or "escape" respectively.