Newbie Question: Make a servo turn 90 degrees and stop.

Tried this...
#include <Servo.h>

Servo myservo; // create servo object to control a servo
// a maximum of eight servo objects can be created

int pos = 0; // variable to store the servo position

void setup()
{

myservo.attach(9); // attaches the servo on pin 9 to the servo object
myservo.write(100);
Serial.begin(115200);
Serial.println("Setup called");

}

void loop()
{

}

Just goes slowly in one direction and doesn't stop.