contains all the knowledge an Irken ever needs to know. It also contains the Irken's job. The Control Brains can re-encode an Irken's PAK to encode the Irken to have a different job, and PAKs function much like a credit card, allowing Irkens to make purchases wirelessly or with a small cord that comes out of the PAK's side.
However, Irkens can only live ten minutes without their PAK before perishing, as all knowledge of how to perform vital processes is held in the PAK. In addition, if any other species were to don one of these PAKs, they would also perish in ten minutes, due to the PAK trying to override their whole systems' inner workings.
In the ten minutes that it takes for an Irken to die without their PAK, many Irkens will spend time customizing their PAKs with new features or, more commonly, spot colors. The Irken tradition of getting one's PAK colored to match one's eyes goes back to a fad started by Almighty Tallest Vak, in which he had his PAK colored with the three spots that are common today rather than the standard at the time: A blank grey PAK. A few Irkens even go to the lengths of changing the shape or overall design of their PAK.