Locations in the document are represented as a line/column number pair, with both indices being zero-based. There are some words for manipulating locations:
+col ( loc n -- newloc )

+line ( loc n -- newloc )

=col ( n loc -- newloc )

=line ( n loc -- newloc )


Miscellaneous words for working with locations:
lines-equal? ( loc1 loc2 -- ? )

validate-loc ( loc document -- newloc )