>>1
GW-BASIC
The only, or last, variant with
FORCED NUMBERING OF LINES.
AFAIK the last version was included with DOS 5.0, because 6.0 started to ship QBASIC, that added a
colorful crappy UI, made line numbers optional, and added "SUB" and "FUNCTION". I still don't understand how they work, and error messages were so misleading that I considered going back to GOTO