Could someone help me understand the output from blockexplorer please

[Justin00]

So I'm still trying to figure out exactly what I am looking at on blockexporer and how it all works etc etc...

I Am looking at transactions for 11.00 BTC that I transfered to someone
http://blockexplorer.com/tx/588ae3330171da854f77c850b8acf3a4e3c78b7296024871ad116332dc917041#o1

I can see 2 inputs... The first one for 10 BTC is from my account. (*edit* I recently recieved 10 BTC at that address, so i guess that would be them)
the second input for 1.3 BTC is from some where I am not familiar with

Then on the outputs there is 0.3 BTC (same figure as the 1.3 but minus the 1 BTC) going to some random place again...
second output is for 11 BTC and its to the person I sent the 11 BTC to, so I am familiar with that account.

I can see the 2 inputs (10 + 1.3 = 11.3) and 2 outputs ( 0.3 + 11 = 11.3) are the same figure.....

Few questions... =) What is the second input ? what is first output ? How did this extra 0.3 come into things ? The person only recieved 11.00 BTC as planned, which is good.

all so confusing  

Any help would be great. I am hoping once I get this it should make all this stuff alot chearer.

thanks

[1714814835]

1714814835

[DeathAndTaxes]

Both inputs are addresses in your wallet.

Bitcoin doesn't work on the concept of "value" in an address it works on the concept of prior outputs.

All inputs all prior tx outputs.

Bitcoin can't spend part of an output.

So your wallet took
A prior tx output worth 10 BTC from one address.
A prior tx output worth 1.3 BTC from a second address.

You spent 11 BTC so that was sent to the receiver's address.  

Remember Bitcoin can't spend part of an output.  You have inputs worth 12.3 and 11 going to the destination so that leaves 0.3 left.  WE call that the "change".

The remaining 0.3 BTC was sent back to YOUR wallet in a brand new (as in never before used) address.

You may not recognize all these addresses because to provide anonymity your wallet will generate a never before used addresses for "change" automatically on each spend.  

[Justin00]

Ok I think I get it, but why was it 11.3 as oposed to 11 ?

thanks heaps

[DeathAndTaxes]

Ok I think I get it, but why was it 11.3 as oposed to 11 ?

thanks heaps

Addresses & wallets don't have unified value that is just an abstraction.  Each input must be a prior TX output.  If your wallet says you have 30.5 BTC it simply means (as an example) your wallet has the following unspent outputs.
10 BTC, 1.3 BTC, 20 BTC, 0.2 BTC.

Your wallet had no outputs that sum up to EXACTLY 11.  If it idid it would have sent that and no change would be needed.  If it had found a set of tx which sum up to 11.1 it would have sent that instead (and given you 0.1 change back).  If the only unspent output you had was a single 10,000 BTC it would have sent that and sent 11 to receiver and 9,989 back to a change address.

Think of each output as a bill.  Lets imagine you wallet has the following bills:
10 BTC bill
1.3 BTC bill
20 BTC bill
0.2 BTC bill

you owe me 11 BTC how would you pay me?  
how much change (in form of new bills) would I have to give you back?
Obviously you have a couple different options but which one makes the most sense?

[Justin00]

aaaaaaaaaaaaaaah I get it now

I'd pay you 11 using 10 + 1.3 and then  get 0.3 in change.

Thanks heaps for taking the time to explain it. The second post really cleared it up.

[Matthew N. Wright]

The correct response to this thread should have been "Use http://blockchain.info".

[arby]

thank you also for explaining, it is indeed very interesting how bitcoin works.

[Justin00]

was having a look at this just now.. thanks for that.
raises more questions though when i search for my IP.. why does it only show a couple of transactions i have sent under "relayed by ip"

The correct response to this thread should have been "Use http://blockchain.info".

[Justin00]

me again =)

Have another question haven't been able to figure out... How does the network know which addresses you have in wallet ?
When you load up client it advertises them or something ?

thanks

[Raoul Duke]

me again =)

Have another question haven't been able to figure out... How does the network know which addresses you have in wallet ?
When you load up client it advertises them or something ?

thanks

All the adresses that were ever used in the network are registered in the blockchain, and you have the whole blockchain in your computer. It just matches all the addresses in your wallet with their respectives blockchain registries and calculates what you have spent and what you still have to spend in each one of them.

You can call the blockchain a ledger, if that's more simple to you.

That's the reason when you load a new wallet into your Bitcoin client you have to tell it to rescan the blockchain and match those addresses in your new wallet to figure out the transactions.

It's pretty neat, the rescan process, as you will see the transactions popping up in your transaction list as your client rescans the blockchain looking for your addresses and finds the transactions

Also, your client has knowledge, sooner or later of ANY transaction that occurs in the network. The transactions that don't match any address in your wallet, it will only save in the blockchain file, the ones that match any of your addresses will also be shown in your transaction list.

It's not your client that broadcasts your addresses, it's more the network that broadcasts all transactions to your client. It just figures out which ones are yours and which aren't

[Justin00]

ah yeah, that makes sense. I should of thought about it abit more

thanks heaps