Access control list

An access control list, in the broadest sense used in computers and security, is a list of entries that specify if some input value is permitted, or forbidden, to perform some action. While the entries can be explicit, as in a list of human names with a given permission, they are commonly bit strings or numbers, and associated with some type of mask. The mask can qualify the match of the incoming value so that either an exact bit match is required, or a "don't care" condition can be specified so the single list entry can match a range of possible inputs.