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Bitcoins

Bitcoin
Bitcoin logo.svg
Prevailing bitcoin logo
ISO 4217
Code XBT
Denominations
Subunit
10−3 millibitcoin
10−6 microbitcoin, bit
10−8 satoshi
Symbol BTC, XBT,BitcoinSign.svg (B͈̎), Ƀ
 millibitcoin mBTC
 microbitcoin, bit μBTC
Coins Unspent outputs of transactions denominated in any multiple of satoshis
Demographics
Date of introduction 3 January 2009; 8 years ago (2009-01-03)
User(s) Worldwide
Issuance
Administration Decentralized
Valuation
Supply growth 12.5 bitcoins per block (approximately every ten minutes) until mid 2020, 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.

Bitcoin is a and a payment system invented by an unidentified programmer, or group of programmers, under the name of Satoshi Nakamoto. Bitcoin was introduced on 31 October 2008 to a cryptography mailing list, and released as open-source software in 2009. There have been various claims and speculation concerning the identity of Nakamoto, none of which are confirmed. The system is peer-to-peer and transactions take place between users directly, without an intermediary. These transactions are verified by network nodes and recorded in a public distributed ledger called the blockchain, which uses bitcoin as its unit of account. Since the system works without a central repository or single administrator, the U.S. Treasury categorizes bitcoin as a decentralized virtual currency. Bitcoin is often called the first cryptocurrency, although prior systems existed and it is more correctly described as the first decentralized digital currency. Bitcoin is the largest of its kind in terms of total market value.

Bitcoins are created as a reward in a competition in which users offer their computing power to verify and record bitcoin transactions into the blockchain. This activity is referred to as mining and successful miners are rewarded with transaction fees and newly created bitcoins. Besides being obtained by mining, bitcoins can be exchanged for other currencies, products, and services. When sending bitcoins, users can pay an optional transaction fee to the miners. This may expedite the transaction being confirmed.

In February 2015, the number of merchants accepting bitcoin for products and services passed 100,000. Instead of 2–3% typically imposed by credit card processors, merchants accepting bitcoins often pay fees in the range from 0% to less than 2%. Despite the fourfold increase in the number of merchants accepting bitcoin in 2014, the cryptocurrency did not have much momentum in retail transactions. The European Banking Authority and other sources have warned that bitcoin users are not protected by refund rights or chargebacks.


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