PaulS:
i intend to use the Arduino to control the motion of five Bipolar stepper Motors
Pretty easy, really. Create 5 instances of the Stepper class, and call step() for the appropriate instance at the appropriate time.
The step() function will toggle the appropriate pins to tell the stepper motor driver to make the stepper motor step.
You do have appropriate stepper motor drivers for your stepper motors, right?
I have L297,L298 and L293 but i haven't yet figured out the best driver.