Bitcoin (abbreviation: BTC; sign: ₿) is a protocol which implements a highly available, public, and decentralized ledger. In order to update the ledger, a user must prove they control an entry in the ledger. The protocol specifies that the entry indicates an amount of a token, bitcoin with a miniscule b. The user can update the ledger, assigning some of their bitcoin to another entry in the ledger. Because the token has characteristics of money,[10][11] it can be thought of as a digital currency