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Previous Block

Introducing the Previous Block field in the block header.

What is the Previous Block​

The previous block refers to the hash value of the preceding block included in the current block header. This field is used to link blocks together to form the blockchain. Each block (except the genesis block) contains the hash value of its previous block, making the blockchain a continuous, immutable record.

Functions of the Previous Block​

1. Forming the Blockchain​

The previous block field allows each block to link to its preceding block, forming a continuous chain. Each block determines its position in the blockchain through the hash value of its previous block.

2. Validating Block Validity​

When a node receives a new block, it checks whether the hash value of its previous block exists and is valid. If the previous block is invalid or nonexistent, the block will be rejected.

3. Preventing Tampering​

Since the block's hash value is generated from the block content, including the hash value of the previous block, any modification to the block content will change its hash value. This makes tampering with any part of the blockchain extremely difficult and costly, as it would require recalculating and changing the hash values of all subsequent blocks.

Importance of the Previous Block in the Blockchain​

1. Ensuring Data Integrity​

The hash value of the previous block ensures the integrity and continuity of blockchain data, allowing all blocks to be sequentially traced.

2. Promoting Consensus Mechanism​

The hash value of the previous block helps network nodes reach a consensus, ensuring that all nodes recognize the same version of the blockchain.

Retrieving Previous Block Information​

Retrieving Block Information​

Using the Bitcoin Core client, you can obtain detailed information about a block, including the hash value of the previous block, with the following command:

mvc-cli getblock <blockhash>

Retrieving Latest Block Hash​

mvc-cli getbestblockhash

Summary​

The previous block field is a crucial part of the blockchain structure. It links each block to form the blockchain, ensuring data continuity and immutability. Understanding the function of the previous block helps to deeply understand the working principles and technical details of the blockchain.