Just to add a little to the correct answers you've already received, all cars have computers from about 1981 on. Most vehicles use a combination of cam and crankshaft sensors. Taking a reading from the crankshaft alone doesn't give the computer all the information it needs in some cases, depending on the fuel and ignition systems in the car. Not only does the computer need to fire the spark plugs at the proper time, it also needs to actuate the fuel injectors at the proper time.