* SOURCE ( -- buffer IN-offset ) the current point of interpret can be gotten through SOURCE. The buffer may flag out TIB or BLK or a FILE and IN gives you the offset therein. Traditionally, if the current SOURCE buffer is used up, REFILL is called that asks for another input-line or input-block. This scheme would have made it impossible to stretch an [IF] ... [THEN] over different blocks, unless [IF] does call REFILL
SOURCE
( -- buffer IN-offset )
REFILL
FORTH/ANS core (dpANS.6.1.2216) ordinary primitive