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I was reading this GitHub book on Bitcoin
They state that "True or False: Only UTXOs can be used as inputs to transactions."
Is the answer, True because you can only spend what you have.
Or False, you can out a spent output in the transaction as input, but the network or the miner will reject it.
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This question makes no sense.
Of course you can make an invalid transaction that doesn't spend an unspent output. If you're fine with calling invalid things transactions, I could just take a piece of random data and call it a transaction.
A valid transaction can only spend unspent outputs.
Thank you, I think I was getting confused. Your concise answer cleared things up for me. – Kyle Graham – 2018-03-19T21:08:29.217
If everyone rejects your transaction, can you call that spending? – alcio – 2018-03-19T17:56:13.607
@alcio no, you can still use it for an input though right? There's nothing stopping you – Kyle Graham – 2018-03-19T18:00:28.597
In a technical sense, yes, you are not limited to the UTXO set for inputs, but in a practical sense, you are if you want your transaction to confirm. – alcio – 2018-03-19T18:31:55.487