Int 21 Fn 5F83  - Lantastic - Get Username Entry                           [N]

   AX = 5F83h
   BX = login entry index (0-based)
   ES:DI -> 16-byte buffer for username currently logged into

Return: CF clear if successful
       DL = adapter number (v3+)
   CF set on error
       AX = error code

Note:  the login entry index corresponds to the value BX used in AX=5F80h

See Also: AX=5F80h