How to control stepper motor?

CODE & CIRCUIT DIAGRAM

 #define A 2

#define B 3

#define C 4

#define D 5

int i=0;

#define NUMBER_OF_STEPS_PER_REV 500

void setup() {

  // put your setup code here, to run once:

pinMode(A,OUTPUT);

pinMode(B,OUTPUT);

pinMode(C,OUTPUT);

pinMode(D,OUTPUT);}

void write(int a,int b,int c, int d) {

  // put your main code here, to run repeatedly:

digitalWrite(A, a);

digitalWrite(B, b);

digitalWrite(C, c);

digitalWrite(D, d);}

void onestep(){

write(1,0,0,0);

delay(2000);

write(0,1,0,0);

delay(2000);

write(0,0,1,0);

delay(2000);

write(0,0,0,1);

delay(2000);

write(0,0,0,0);

delay(2000);

write(1,1,0,0);

delay(2000);

write(1,1,1,0);

delay(2000);

write(0,0,0,1);

delay(2000);

write(1,0,1,0);

delay(2000);

write(0,1,0,1);

delay(2000);

write(0,0,0,0);

delay(2000);

}

void loop(){

while(i< NUMBER_OF_STEPS_PER_REV){

onestep();

i++;

}}