What address displays when you send a coin?

[venom]

Sorry if this has been answered before, I did search and couldn't find a straight answer.

Basically, using a tool such as blockexplorer.com I was trying to figure out what address or identifying information is displayed in a send transaction.  I know it doesn't show up in the Bitcoin client, but I do remember reading that some kind of information is in the publicly viewable block chain, using a tool like blockexplorer.  So for instance I sent 1BTC to an exchanger earlier.. which address shows as being the 'sender' address in the public block chain?  That's my 1st question.. the next question is, can we choose/create a new sending address for each send transaction?

[grue]

you can't control what addresses you send from. All of the coins you sent is from addresses that you received coins with.

[Rob P.]

Said another way.  The address that has the coins that you're sending will be displayed as the sending address.

If you wish to control the address, then you need to move the coins from one address to another prior to sending them.

[unfinishe]

Actually, I think you can control the address that you send from if you use "bitcoind.exe" with the command "sendfrom". https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_calls_list

[Pieter Wuille]

Actually, I think you can control the address that you send from if you use "bitcoind.exe" with the command "sendfrom". https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_calls_list

You cannot, sendfrom simply indicates which account's balance to deduct the amount from. It has nothing to do with which coins are selected.

Also, bitcoin technically does not have a "from address". Assuming it was a standard transaction, you can look up which address the input coins were last sent to, but there may be multiple input coins, and each can have one address, multiple addresses (eg. in contracts) or no address at all. These do require non-standard transactions though.