Transactions have multiple inputs and outputs.
If you have 0.5BTC inputs, then 50 of them will be bundled together and a transaction with 50 inputs and one output will be created.
... but that's not what will actually happen. A 50-input-transaction will be over the "small enough to be free" transaction size limit, so 51 will be bundled together and a transaction with 51 inputs and two outputs (one to the destination, one back to you for any change leftover after paying the transaction fee) will be created.
There is no ledger, there are just transactions with inputs and outputs. Your bitcoin balance is the sum of all the outputs to addresses that you own that haven't yet been used as input to another transaction.