Help with placing a function please I am trying to call a function that will turn a stepper motor a number of steps depending on the value submitted through the serial console. For an example, if I submit 50, the motor should turn 50 steps clockwise (and counter clockwise for  a negative value).

#include &lt;Stepper.h&gt;
#define STEPS 200
Stepper stepper(STEPS, 8, 9, 10, 11);

int serial_input = Serial.read();

void setup() {
Serial.begin(9600) ;
stepper.setSpeed(30);
}

void loop() {
}

void turnMotor(serial_input){
  stepper.step ( serial_input ) ;
}  


And here are the errors I get:

Motor4.ino:12:28: error: variable or field ‘turnMotor’ declared void
Motor4.ino:12:16: error: ‘serial_input’ was not declared in this scope
Motor4.ino:117:28: error: variable or field ‘turnMotor’ declared void


Thank you
As Juraj already explained, you cannot use Serial.read() outside a function.

What you probably want is to call it within the loop, or a function called from loop (via other functions).
Than you can call also turnMotor from Loop or a function called from loop. The value (int serial_input) probably doesn't have to be global anymore, but that depends on the time where you assign the value and where you call turnMotor.