BITCOIN

Bitcoin is a worldwide cryptocurrency and digital payment system[13]:3 invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto.[14] It was released as open-source software in 2009.[15]

Bitcoin
Bitcoin logo.svg
Prevailing bitcoin logo
ISO 4217
Code XBT[a]
Denominations
Subunit
 10−3 millibitcoin[1]
 10−6 microbitcoin, bit[8]
 10−8 satoshi[9]
Symbol BTC,[note 1] XBT,[note 2] ₿ (U+20BF, BitcoinSign.svg)[note 3]
 millibitcoin[1] mBTC
 microbitcoin, bit[8] μBTC
Coins Unspent outputs of transactions denominated in any multiple of satoshis[7]:ch. 5
Demographics
Date of introduction 3 January 2009; 8 years ago
User(s) Worldwide
Issuance
Administration Decentralized[10][11]
Valuation
Supply growth 12.5 bitcoins per block (approximately every ten minutes) until mid 2020,[12] and then afterwards 6.25 bitcoins per block for 4 years until next halving. This halving continues until 2110–40, when 21 million bitcoins will have been issued.
^ Unofficial.
File:Bitcoin explained in 3 minutes.webmPlay media
Bitcoin explained in 3 minutes
The system is peer-to-peer, and transactions take place between users directly, without an intermediary.[13]:4 These transactions are verified by network nodes and recorded in a public distributed ledger called a blockchain. Since the system works without a central repository or single administrator, bitcoin is called the first decentralized digital currency.[13]:1[16]

Besides being created as a reward for mining, bitcoin can be exchanged for other currencies,[17] products, and services in legal or black markets.[18][19]

As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.[20] According to research produced by Cambridge University in 2017, there are 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[21]