standar and continous servo

I was just learning the Arduino. I connect Arduino with a standard servo and continuous servo. standard servo rotates from 0 - 180 degrees and then back to 0. continuous servo rotate continuously. why??. I want to be a continuous servo rotates from 0 - 180 degrees and 0.

#include <Servo.h> 
#include <NewSoftSerial.h>
 
Servo standarservo;  
Servo continousservo;     
int pos = 0;   

void setup() 
{ 
 Serial.begin(115200);
  standarservo.attach(9);  
  continousservo.attach(10);
} 

 
 
void loop() 
{ 
  Serial.println("forward");
  for(pos = 0; pos < 80; pos += 1) 
  {                                  
    standarservo.write(pos);             
    continousservo.write(pos);
    delay(15);                      
  } 
  delay(3000);
  Serial.println("back");
  
  for(pos = 80; pos>=0; pos-=1)    
  {                                
    standarservo.write(pos);             
    continousservo.write(pos);
    delay(15);                       
  } 
  delay(3000);
}

I want to be a continuous servo rotates from 0 - 180 degrees and 0.

Standard and continuous servos operate drastically different. A standard servo can be commanded to go to any specific position between 0 and 180 degrees and stop there and hold that position until a new different position command is sent.

A continuous servos is not really a servo anymore due to its modification. A 0 position command will have it turn at some maximum speed in one direction, a 180 position command will have it go some maximum speed in the opposite direction, and a 90 position command will cause it to stop turning. You no longer have the ability to control a continuous servo to move to a specific position and stop. It has been converted such that it's actually a variable speed bi-direction geared motor, nothing more, nothing less, not a servo.

To be able to move to 0 then 180 and then back to 0 either once or continuously requires a standard servo, not a continuous servo.

I suspect many beginners to this hobby purchase 'continous rotation' servos thinking they are getting a 'standard' servo with some extra added feature, when in fact they are getting something entirely different that can no longer function the same as a simple servo. One proper application for a continuous rotation servo is to drive a wheel for motion control on a small car or robot, usually used in pairs.

Lefty