Software
Main article: Bitcoin network
Electrum – sample bitcoin client
Bitcoin client software called a bitcoin wallet allows a user to transact bitcoins. A wallet program generates and stores private keys, and communicates with peers on the bitcoin network. The first wallet program called Bitcoin-Qt was released in 2009 by Satoshi Nakamoto as open source code.[41] It can be used as a desktop wallet for payments or as a server utility for merchants and other payment services. Bitcoin-Qt, also called Satoshi client is sometimes referred to as the reference client because it serves to define the bitcoin protocol and acts as a standard for other implementations.[41] As of version 0.9, Bitcoin-Qt has been renamed Bitcoin Core to more accurately describe its role in the network.[42] When making a purchase with a mobile device, QR codes are used ubiquitously to simplify transactions. Several server software implementations of the bitcoin protocol exist. So-called full nodes on the network validate transactions and blocks they receive, and relay them to connected peers.[41]