In this paper the number of directions determined by a set of q-n poin
ts of AG(2, q) is studied. To such a set we associate a curve of degre
e it and show that its linear components correspond to points that can
be added to the set: without changing the set of determined direction
s. The existence of linear components is guaranteed by Well's theorem
concerning the number of GF(q)-rational points of an absolutely irredu
cible curve, if it is small enough. (C) 1996 Academic Press, Inc.