first you need to find the type of stepper you are using.
incase of unipolar stepper then
the control algorithm willbe
if(condition for forword)
while(condition for forword)
{
control port=0x11; 0001
delay(); define as per the motor
control port=0x22; 0010
delay();
control port=0x44; 0100
delay();
control port=0x88; 1000
delay();
if(condition for backword)
while(condition for backword)
{
control port=0x88; 1000
delay();
control port=0x44; 0100
delay();
control port=0x22; 0010
delay();
control port=0x11; 0001
delay();
}