Thanks! am dl'ing now.

While I'm waiting (re dl'ing the blockchain, was having problems with dbase errors) I am wondering exactly how bitcoin transactions are formatted.

Does the entire output of a transaction have to be spent when using it as an input for a new transaction? If so can the address of that original output be an output on the subsequent transaction ie. returning the change to the original address?

Working with offline wallet concept so will be generating and signing raw transactions through the API.