4 Wheel robot car basic example

http://arduinolearning.com/robots/4-wheel-robot-car-basic-example.php

#include <AFMotor.h>
 
AF_DCMotor motor1(1, MOTOR12_64KHZ); // create motor #1, 64KHz pwm
AF_DCMotor motor2(2, MOTOR12_64KHZ); // create motor #2, 64KHz pwm
AF_DCMotor motor3(3, MOTOR34_1KHZ); // create motor #3, 1KHz pwm
AF_DCMotor motor4(4, MOTOR34_1KHZ); // create motor #4, 1KHz pwm
 
void setup()
{
  Serial.begin(9600);//set up Serial library at 9600 bps
  Serial.println("Motor test!");
  MotorSpeed(200);
  AllForward();
  delay(1000);
  AllBackward();
  delay(1000);
  AllStop();
  delay(1000);
}
 
void loop() {
 
}
 
void MotorSpeed(int Speed)
{
  motor1.setSpeed(Speed);     // set the speed to 200 (255 max)
  motor2.setSpeed(Speed);
  motor3.setSpeed(Speed);
  motor4.setSpeed(Speed);
}
 
void AllForward()
{
  Serial.print("forward");
  motor1.run(FORWARD);      // turn it on going forward
  motor2.run(FORWARD);
  motor3.run(FORWARD);
  motor4.run(FORWARD);
}
 
void AllBackward()
{
  Serial.print("backward");
  motor1.run(BACKWARD);      // turn it on going forward
  motor2.run(BACKWARD);
  motor3.run(BACKWARD);
  motor4.run(BACKWARD);
}
 
void AllStop()
{
  Serial.print("stop");
  motor1.run(RELEASE);      // turn it on going forward
  motor2.run(RELEASE);
  motor3.run(RELEASE);
  motor4.run(RELEASE);
}