Controlling Stepper Motor Position w/ Push Buttons

Sorry for not simply posting the code, I was unaware how. I have made the semi-colon correction.

//In this sketch I wish to control a stepper motor using my Arduino Mega 2560 R3, utilizing four push button switches.

#define DIR 22 //setting the direction output of stepper (DIR) to pin 22
#define STP 2  //setting steps output of stepper motor (STP) to pin 2
#define PB1 25 //setting input of push button switch one (PB1) to pin 25
#define PB2 26 //setting input of push button switch two (PB2) to pin 26
#define PB3 27 //setting input of push button switch three (PB3) to pin 27
#define PB4 28 //setting input of push button switch four (PB4) to pin 28

void setup()
{
  pinMode(DIR, OUTPUT);
  pinMode(STP, OUTPUT);
  pinMode(PB1, INPUT);
  digitalWrite(PB1, HIGH);
  pinMode(PB2, INPUT);
  digitalWrite(PB2, HIGH);
  pinMode(PB3, INPUT);
  digitalWrite(PB3, HIGH);
  pinMode(PB4, INPUT);
  digitalWrite(PB4, HIGH);
}
void loop()
{
  byte a=!digitalRead(PB1);
  byte b=!digitalRead(PB2);
  byte c=!digitalRead(PB3);
  byte d=!digitalRead(PB4);
  int stepperPosition0=400;
  int stepperPosition1=(stepperPosition0+400);
  int stepperPosition2=(stepperPosition1+400);
  int stepperPosition3=(stepperPosition2+400);
  
  if (a==1)                             //if PB1 is pressed
  {
    digitalWrite(STP,stepperPosition0); //stepper motor will go to position 0
  }
  else if (b==1)                        //unless PB2 is pressed
  {
    digitalWrite(STP,stepperPosition1); //then stepper motor will go to position 1
  }
  else if (c==1)                        //unless PB3 is pressed
  {
    digitalWrite(STP,stepperPosition2); //then stepper motor will go to position 2
  }
  else if (d==1)                        //unless PB4 is pressed
  {
    digitalWrite(STP,stepperPosition3); //then stepper motor will go to position 3
  } 
}

Can anyone tell me if I'm sending the signal to the EasyDriver Stepper Motor Driver correctly so that the stepper motor will actually move? I feel as if the 400 micro step increments are unit-less in the code I have written and my Arduino will not know what to do with that value. Will it essentially ask "400 what?", and if so, how can I assign 400 a unit so it realizes what action to carryout.