# BTC(Bitcoin) * Issue Time 2008-10-31 * Total Supply 21,000,000 BTC * Circulation 19,277,550 BTC * White paper * Website * Block Explorer Bitcoin is a cryptocurrency and a digital payment system invented by an unknown programmer, or a group of programmers, under the name Satoshi Nakamoto.It was released as open-source software in 2009.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 a blockchain. Since the system works without a central repository or single administrator, bitcoin is called the first decentralized digital currency.Besides being created as a reward for mining, bitcoin can be exchanged for other currencies, products, and services in legal or black markets.As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment. 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. {% hint style="info" %} Trade on ZKE Exchange：; Twitter： Telegram： {% endhint %} --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.zke.com/symbol/btc-bitcoin.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.