how do I unlock my macbook air system lock pin code?
After a while when I turned on my MACBOOK air, it prompted for a FOUR digit code to unlock. Please help me resolve the issue
MacBook Air, iOS 8
If you forget your firmware password
If you can't remember the password you set using the Firmware Password Utility or Find My Mac, schedule a service appointment with an Apple Retail Store or Apple Authorized Service Provider. Bring your proof of purchase (original receipt or invoice) with you. If you plan to visit an Apple Retail Store, make a reservation (available only in some countries).
From here > Use a firmware password on your Mac - Apple Support