Steppermotor connect with 89c51

i am working on robotics project and today i am searching about microcontroller. so plz help me .
i want a complte description about atmel 89c51 how we connect stepper motor to atmel89c51 and in one atmel 89c51 we connect only one motor or either we connect 3 or 4 motors in single atmel 89c51? and i also want to know about the stepper motor why we use a unipolar steper .