*ACS stands for Antoniak Coding System and attempts to classify and code everything in the world starting with People, Locations, Events, Things and Abstractions. Each of the above categories in turn is further broken down into logical sub categories with particular attention paid to making sure that each subcategory within the parent category starts with a mutually exclusive different pair of letters.

People as a category is broken down into Leaders, Artists, Authors, Scientists, Discoverers Athletes and Nefarious People. The first sub category for People is the highest and most notable thing the person is famous for. For George Washington, as an example, it would be President and not General. However, because of the fact that multiple codes can be used, he can have both codes.

Each subcategory in turn is further broken down as far as is necessary to define the category of the Round. A president of the United States would be People, Leader, Political, US, President-Vice President and First Lady. A congressman would be People, Leader, Political, US, Congressman. General Patton would be People, Leader, Military, Army, General, US. A governor of California would be People, Leader, Political, US, State, CA, Governor

Each of these categories are represented by their first two letters. In the above examples they are bold. A President of the US would be PeLePoUSPr and the Governor of California would be PeLePoUSStCAGo.

There is one field in each Round devoted to categories but it can have multiple sets of codes. A presidential assassination would have a code to cover the fact that it is about a president, a code that it was a historical event, a code that it was a disaster, and a code that it involved a person dying. If the location was important, that too might have its own set of codes Location Historic etc.

In addition to the Category field in a Round, there is a Education field that answers the question "In what school class would this be taught?". This too is broken down by two letter pairs. An item on a presidential assassination might carry an Education code of HiUS20 for History, US, 20th Century. In as much as this would also be a world important event, it might also carry an Education code of HiWo203Q for History, World, 20th Century, 3Q-3rd Quarter.

What about pair letter conflicts? Well they do exist, but in most cases there are ways around them, usually by using a different word to define the category. Locations could also be places for example. If that doesn't work, then we use a substitute letter and a dash and then the correct word. Baseball is Ba, basketball is BK-Basketball. This works especially well for state codes like AZ-Arizona for Arizona etc.

There are three other fields devoted to defining a Round and they are Geographic Area -GeoCode, Trivia Code -TrivCode and Key Words. The GeoCode and TrivCode follow the same convention as the ACS code.