Bitcoin is a worldwide cryptocurrency and digital payment system[13]:3 called the first decentralized digital currency, since the system works without a central repository or single administrator.[13]:1[14] It was invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto[15] and released as open-source software in 2009.[16] 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.
Besides being created as a reward for mining, bitcoin can be exchanged for other currencies,[17] products, and services. As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.[18] Bitcoin can also be held as an investment. 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.[19] On 1 August 2017 bitcoin split into two derivative digital currencies, the classic bitcoin (BTC) and the Bitcoin Cash (BCH).[
