To understand NCU, first you have to undertand what a Nano Program is.

A Nano Program is any 'spell' or 'nano' that is currently running on your character.

Now, every nano program takes a certain amount of space. Obviously it wouldn't do to have every buff in the game running on a level 1 character ;).

Everyone in AO started the game with 0/8 NCU. This means that they have 8 slots to run nano programs in, and 0 of them are being used. If someone cast a nano program on you that buffed (raised) your hp, your NCU would perhaps change to 2/8. This shows that two of your NCU slots are being used to run a nano program.

All nano programs in Anarchy Online have a timer that tells you when the nano program will terminate. Upon termination of the nano program, it will also cease taking up room in your NCU. So, once the hp buff runs out, your NCU would go back to 0/8, showing that you have no nano programs running.

So, the natural question becomes, 'How do I get more NCU?'. Well, that's where belts and NCU Memory comes in!

A belt is an item worn on the belt slot of the character that determines which slots are open to put NCU Memory in. NCU Memory is an item that raises the users MAX NCU and goes in a spot specially designed to hold NCU. (Called NCU Slots)

You'll hear them referred to as a '4 slot belt' or a '3 slot belt'. The maximum number of slots that a belt can open up is 6. This allows 6 NCU Memory chips to be put in. Each chip adds a specific amount to the users max NCU. The amount added can range from +1 ncu to +64 on normal NCU chips. (There are special types that add more, but those are for very high levels).

To put in either NCU Memory Chips or an NCU Belt, you'll need IP in the skill 'Comp. Lit'. This is a very important skill for every profession.