The Digital World: I - Bitcoin: from history to real live.

Summary Bitcoin can be considered as a medium exchange restricted to online markets, but it is not a unit of account and a store of value, and thus cannot be considered as a money. Bitcoin value is very volatile and traded for different prices in different exchanges platforms, and thus can be used for arbitrage purpose. His behavior can be associated with a high volatile stock, and most transactions in Bitcoin are aimed to speculative instruments. The high volatility in Bitcoin and the occurrence of speculative bubble depend on positive sentiment and confidence about Bitcoin market: several variables may be considered as indicators (volume of transactions, number of transactions, number of Google research, wikipedia requests). The star of the crypto-currencies has attained the 19 716 dollars in December 2017 and decreased to 6 707 dollars March 29, 2018. In capitalization it is at this time the 30th mondial currency. We explain some limits and interests of the Bitcoin system and why the central bankers and regulators need to take some decision on its existence, and what could be the possible evolution of the Bitcoin Blockchain.