Bitcoin Forum

So I was starting to read Andreas' Antonopoulos' "Mastering Bitcoin" (http://"https://github.com/bitcoinbook/bitcoinbook/blob/develop/ch02.asciidoc") and I was wondering about this diagram:

https://i.imgur.com/ETdiSwm.png

Quoting from the book


My question is:
 ???

Does "Output 1" mean that there will be a new "Input" for Alice's account?

Umm... from what I understand there, this is your own wallet. You are Alice.
So I see that input 1 as the change from an older transaction of yours. (you'll understand this later).

You send money to Bob, but less than your total, hence you create one output (1) that'll be sent to Bob and one output (2), the change, back to yourself.
So this output 2 is money you have sent to yourself. So the wallet sees as money coming to you, or, as an input.
This input can be seen then as input 2. And you can make from it new transactions, like you've done with input 1. And maybe the starting part is clearer too.

All this is "somewhere in the middle" of the "life" of your coins, since at very start, the first input to your wallet clearly came from elsewhere (let's say from John).

This was a transaction involving change and that's why it may be a bit confusing.
If it's the first transaction from the "chain", then we'll have:



Edit:
* If I was not clear, please ask further. I know that sometimes I don't explain best.
* Your link to the is broken, you may want edit the post and fix it = remove the quotes and the extra http:// part.

I think the change output is what are you talking about?

Yes, it will become input again if you create another transaction for now it's output. It's just like you are buying shoes at a price of $59 but you don't have the exact amount of $59 and you only have $100. You pay $100 to the seller and you will get a change amount of $41.

It's the same as what Bitcoin transaction works.

Just adding this sample image below to understand it a bit

https://i.imgur.com/bKRwu9Q.png

This is another image below

https://cryptoarmy.io/wp-content/uploads/2021/12/Instead-Andreas-sends-Alex-all-3-Bitcoins-and-receives-2-Bitcoins-in-balance..png
Source: https://cryptoarmy.io/how-does-instant-bitcoin-transaction-work-worldly/

Just adding to this  answer.
A single address may also have multiple inputs (or UTXO).

For example,  if you receive multiple payments in the same address (such a donation address ) each donativo  will be a new output or a new input (if spent in a transaction)

Take a look at this example:
Wikileaks donation address has multiple outputs
https://blockchair.com/bitcoin/address/36EEHh9ME3kU7AZ3rUxBCyKR5FhR3RbqVo

There are no inputs, only outputs.  8)

Output can be an old address or a change address. The latter one (change address) is recommended to use. If you create and use multiple addresses in a single wallet, Output 1 can be use as input or part of inputs for your future transactions.

You can use a whole Output 1 or part of it and then you will have another change address as Output 2 from leftover of Output 1.

Yes, but it is Alice wallet.

Assuming you are Alice, you were sent 1 BTC. You sent 0.4 BTC to Bob, the 0.4 BTC output you sent to Bob will becoming input for Bob and Bob will be able to spend from it. But not only that, the remaining 0.6 BTC will be sent back to change address generated on your wallet which is what you are referring to. Anytime you want to spend again, you can spend the change address utxo.

It won't become input if you receive a change in your wallet it would be still an output or we can call it (Unspent transaction output)UTXO.

It only becomes inputs when you make a transaction just like what you see on the image above as a sample.

Never mind my mistake. I absolutely agree, both the bitcoin sent to 'Bob' and 'Alice change address' are both utxo.