Do we’ve got to look all transactions of Alice saved on blocks and to calculate her steadiness

No one aside from Alice cares about her steadiness. That is as a result of Bitcoin is money, not a checking account. If you hand over a $10 banknote to a shopkeeper, they do not need to know the way a lot whole money you’ve gotten in your pockets, they only have a look at the $10 to see whether it is real. Bitcoin doesn’t preserve monitor of steadiness per account holder – there aren’t any accounts, no folks, no balances within the Bitcoin community or blockchain.

Bitcoin works on the idea of retaining monitor of Unspent Transaction Outputs (UTXOs). A UTXO is roughly equal to a banknote or coin. When somebody spends a UTXO, all different nodes examine that the UTXO exists and hasn’t been spent already.

You may create a listing of UTXOs by studying the blockchain from the beginning as soon as.

A Bitcoin pockets resembling Bitcoin core might present strategies of wanting on the knowledge in its copy of the blockchain. For instance Bitcoin core has an RPC API together with capabilities resembling getreceivedbyaddress – which usually solely works by yourself addresses, not different folks’s.

there are instruments to know the steadiness of an adress. However my query is how this instruments works ? How they request the blockchain?

They will use the Bitcoin community protocol to gather their very own copy of the blockchain, index it after which carry out their very own evaluation of that knowledge.

The Bitcoin community protocols enable any new node, resembling a pockets, to find just a few different nodes and to request from them copies of blockchain knowledge, piece by piece.

Typically talking, deal with balances are of no curiosity in any way. They play no half in the way in which Bitcoin operates. You would possibly rummage by your pockets and rainy-day coin-jar to write down down the whole sum of money you discover however nobody else actually cares.