As mobile technology becomes widespread and computers are getting smaller the advantages of mobile learning are getting common. How can we use this new technology in mathematical instruction? Our review covers three topics. (1) Computers can be used as textbooks with the possibilities of hypertext and pictures. (2) Computers can be effective interactive instructors teaching (a) facts and (b) procedures though they are quite bad at (c) complex processes of understanding. Finally it can be used as (3) a teaching aid (like calculators) though the usefulness of such function is debated. The possible applications and assertions about them mentioned above are supported by recent findings in cognitive science like multiple representation (analogue, verbal and symbolic) and sophisticated processing mechanisms.