# Could someone explain how the TX operation here works?

I know this is a BCH address, but it's the best example I could find. The same concept holds for BTC, so understanding what's going on is relevant.

https://explorer.bitcoin.com/bch/tx/5d0af59f43f8e8388839518243c743279e7c3dd526385fcc5bbcd907cd61bd2a

What one sees is one transactions with two inputs and two outputs.

1. How does it happen that there are multiple inputs/outputs in a transaction?
2. How did `12WsyKG89bxTGWV1iguxPWh6UX2ye1X8hD` end up with 208.448 and `18Q43boBRU8Sk57SjSfjgFbjvXhBccBrKq` with 18.816 - where in that transactional data does it specify which address gets what from the inputs?

## 1 Answer

• Multiple outputs are usual, just like e-mail.

• If one of your friends has sent you 5 BTC, and another friend has sent you 2 BTC, you should combine and spend them if you need to buy something for less than 7 BTC and greater than 5 BTC.

(By the way, do you know what a change is?)

• There is no "This output gets its value from this input" All input values are summed, then spent.
• Thank you for the link to Change. I was aware of it, but the link provided a much better explanation. If all inputs are summed, do we assume that all inputs are from the same account holder/entity? Mar 18, 2018 at 7:18
• @EvilJordan No, take a look at SIGHASH_SINGLE. It's how CoinJoin works. For more information: en.bitcoin.it/wiki/CoinJoin Mar 18, 2018 at 7:37
• Thanks for walking me through this. I thought I understood how this worked, but it's suddenly become a lot more complex. So, from what I gather, if Bob has 2 BTC and wants to send Alice 1 BTC, somehow Tom, with his 1 BTC he wants to go to Jane can also get in the mix, and a transaction will show two inputs (Bob:2, Tom:1) and three outputs (Alice:1,Bob(change):1,Jane:1). I guess my question is how did Tom's transaction to Jane end up in the mix? Is the software doing that to save on bandwidth? Mar 18, 2018 at 7:57
• @EvilJordan Oops, CoinJoin uses SIGHASH_ALL. If you're looking for how CoinJoin works, here's the answer. bitcoin.stackexchange.com/a/57276/38618 Mar 18, 2018 at 8:33
• Did you initially bring up CoinJoin because this particular transaction I referenced is using it? Seems like a very niche service. Mar 18, 2018 at 17:46