Project 10 off book Zoetrope

Hardware The Arduino Starter Kit
1

I have made the programming like in the book but I get an error

void loop() {
onOffSwitchState = digitalRead(onOffSwitchStateSwitchPin);
delay(1);
directionSwitchState = digitalRead(directionSwitchPin);
motorSpeed = analogRead(potPin)/4;

if(onOffSwitchState ! = previousOnOffSwitchState) { // error: expected ')' before '!" token
this is the error place

if(onOffSwitchState == HIGH) {
motorEnabled = !motorEnabled;

I have programmed it like in the book, so I think I make a mistake but I don't know what the mistake is.

Thank you for helping me.

2

Dear All,

I found the problem.

It's not ! =
but !=