Battery terminal corrosion prevention

I believe all modern cars use the negative side as a ground, but, not vehicles are that way. I know many of the older British cars (among others) used the positive side as a ground. Also, keep in mind that on computer controlled cars with various smog sensors, disconnecting the battery resets them to a default mode that takes a certain amount of miles and cycles to get them running in peak performance again. This is important if you have to get the car smogged at a test station. Without proper sensor output to the computer, the test will fail.