# 4.4 Data structure

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Header: Used to identify a specific block in the entire blockchain. Processes all blocks in the blockchain. As part of routine mining operations, miners periodically hash block headers by changing the nonce value.

Previous block address/hash: Used to connect the i+1th block and the ith block using a hash. That is, it is a reference to the hash of the previous (parent) block in the chain.

Timestamp: A system that verifies the data contained in a block and assigns the time or date of creation to a digital document.

Nonce: A nonce number that is used only once. This is a key part of the POW within the block. If it is less than or equal to the current target, it is compared to the live target.

Merkel Root: A type of data structure composed of various data blocks. Merkle trees store all transactions in blocks by creating a digital fingerprint of the entire transaction. This allows users to verify whether a transaction can be included in a block or not.


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