Ok that makes sense, thank you. Can you tell me whether it's possible to combine tiny BTC amounts in your wallet and spend them? Say you have ten 0.00010
BTC amounts, can you make them into one 0.0010
BTC?
Also you did not answer this part, do you care to?
"How does the entire world know that I received 2.0 mBTC, sent 0.4 mBTC, and am only left (of the original 2.0 mBTC) with only 0.6 mBTC? Is that supposed to be public knowledge? And, as before, why are such big amounts taken from my initial sum, just for sending small micropayments?
I am left with 0.6 mBTC (in my Blockchain.info wallet) + 0.4 mBTC (in my online wallet) = 1.0 mBTC out of a initial sum of 2.0 mBTC, so half my money was taken by the miners in just one micro transaction?"
To answer the first question.
Bitcoin does it automatically when it gathers the change it searches for the unspent outputs then lumps them all together to make that 0.001
(Assuming they are all in the same wallet of course)
(If you wait long enough and get coin age you can do it for free but its a factor of time and priority on the network so the fee speeds it up)
__
Second Part
(small error) 1.6 I believe not 0.6
It's confirmed in the blockchain the ledger records that you recieved 2.0 mbtc from someone then it records that you sent 0.4 mbtc to someone else and deducts that amount from the ledger so the amount of unspent transactions is 1.6 mBtc. The miners all observe this transaction and confirm that you sent it to Bob and he recieved the balance. So yep the record of the transaction is recorded and public knowledge, the person behind the address is unknown usually hence psuedo anonymous.
And with small amounts the transaction fee would probally eat the remainder.
As mintxfee 0.0001 (BTC)
https://en.bitcoin.it/wiki/Transaction_feesSending
A transaction may be safely sent without fees if these conditions are met:
## It is smaller than 1,000 bytes.
## All outputs are 0.01 BTC or larger.
## Its priority is large enough (see the Technical Info section below)
Otherwise, the reference implementation will round up the transaction size to the next thousand bytes and add a fee of 0.1 mBTC (0.0001 BTC) per thousand bytes[1]. As an example, a fee of 0.1 mBTC (0.0001 BTC) would be added to a 746 byte transaction, and a fee of 0.2 mBTC (0.0002 BTC) would be added to a 1001 byte transaction. Users may increase the default 0.0001 BTC/kB fee setting, but cannot control transaction fees for each transaction. Bitcoin-Qt does prompt the user to accept the fee before the transaction is sent (they may cancel the transaction if they are not willing to pay the fee).
Also as a note
If your using an older Bitcoin client it has a higher default transaction fee than the new ones
So its possible it used 1 MBTC as the fee.
https://bitcointalksearch.org/topic/bitcoin-qt-bitcoind-082-final-available-219504From 0.8.2 onwards fee dropped from 0.0005 to 0.0001