What causes code?

What causes code?
A vehicle's computer will give the mechanic specific codes but usually the underlying problem is obvious to you; for example if you unplug the electrical in seats in most newer cars, it will turn on the airbag light which will send codes to your mechanic when hooked up to their diagnostic equipment. These codes usually allow the mechanic to electronically reset the computer in the vehicle therefore turning off the dashlight, or whatever caused the computer to trip electronically... have you had the mechanic hook your car to the computer? They should know what the code means if they have the right equipment..........Hope this helps, wish you question was more specific. If your car's radio screen reads, CODE, this is usually due to a dead battery and happens the first time you go to turn radio back on......