Those coming from a Windows device may be used to using a pin code to log in. ChromeOS has that option, too. You’ll need to set it up first.
To do it…
 On the ChromeOS device, go into Settings.
 In the People section, select Screen lock.
 Tap or click the Pin or Password option and tap or click the Set Up Pin button.
 Enter your password, and then select Confirm.
 Select PIN or password Set up PIN.
 Enter a PIN of six digits or more, and then select Continue.
 Re-enter your PIN, and then select Confirm.
Now when you log in or come out of standby, you’ll be prompted with a number pad where you can either enter your Pin or your Password.
If you go 24 hours without accessing the ChromeOS device, you’ll need to enter your password (instead of the Pin) again.