AUTO [start|.][, [increment]]
Automatic line numbering for manual program entry. If the line already exists, then an asterisk is displayed and pressing ENTER leaves the line as-is. If the line does not exist, then an asterisk is not displayed and pressing ENTER skips to next line. AUTO mode is terminated by any ERROR or by pressing Control-C.
If start argument omitted, then 10 used as default. Dot means usage of last entered line in auto mode.
If increment argument omitted, then 10 used as default.