This post is written in Chinese. Please consider using Google Translate

自從比特幣火起來以後，網上對比特幣的解釋可謂汗牛充棟，紛繁複雜。但對於程序員來說，最直接的方式莫過於直接看程序代碼了。嫌比特幣代碼龐雜沒關係，我找到一段簡明扼要的代碼，用來理解比特幣再好不過了。

以下這段程序轉自知乎上Wu Hao的回答。

function mine()
{
    while(true)
    {
        longestChain = getLongestValidChain()

        -- A number that changes every time, so that you don't waste 
        -- time trying to calculate a valid blockHash with the same
        -- input.
        nonce = getNewNonce()

        currentTXs = getUnconfirmedTransactionsFromNetwork()

        newBlock = getNewBlock(longestChain, currentTXs, nonce)

        -- http://en.wikipedia.org/wiki/SHA-2
        -- and this is what all the "mining machines" are doing.
        blockHash = sha256(newBlock)

        if (meetReqirements(blockHash))
        {
            broadcast(newBlock)
            -- Now the height the block chain is incremented by 1
            -- (if the new block is accepted by other peers),
            -- and all the TXs in the new block are "confirmed"
        }
    }
}
////////////////////////////////////////////////////////////////
function sendBTC(amount)
{
    sourceTXs = pickConfirmedTransactionsToBeSpent(amount)
    tx = generateTX(sourceTXs, targetAddrs, amount, fee)
    signedTx = sign(tx, privateKeysOfAllInputAddress)
    broadcast(signedTx)
}
////////////////////////////////////////////////////////////////

下面是我的解釋：

挖礦過程就是不斷從比特幣網絡中獲取所有未確認交易getUnconfirmedTransactionsFromNetwork()，把它們打包成一個區塊並掛載目前最長的區塊鏈上getNewBlock(longestChain, currentTXs, nonce)，然後計算新的區塊的散列值sha256(newBlock)，如果散列值正好滿足挖礦難度了meetReqirements(blockHash)，那麼就挖礦成功了。所謂挖礦難度，指的是要求的二進制散列值小於某個閾值，閾值越小，挖礦的難度就越大。

付款過程就是把一些有餘額的已確認交易拿出來作爲發送地址pickConfirmedTransactionsToBeSpent(amount)，然後根據目標地址支付一定交易費生成新的交易generateTX(sourceTXs, targetAddrs, amount, fee)，並用錢包私鑰對交易簽名sign(tx, privateKeysOfAllInputAddress)，然後廣播出去。