Blocks

Blocks are an important concept in Ethereum. They are containers for a transaction. A block contains multiple transactions. Each block has a different number of transactions based on the gas limit and block size. The gas limit will be explained in detail in later sections. The blocks are chained together to form a blockchain. Each block has a parent block, and it stores the hash of the parent block in its header. Only the first block, known as the genesis block, does not have a parent.

A typical block in Ethereum is shown in the following screenshot:

Figure 1.12 – A typical block in Ethereum

There are a lot of properties associated with a block, providing insights and metadata about it, and the following are some of the important properties along with their descriptions:

• The difficulty property determines the complexity of the puzzle/challenge given to miners for this block.
• The gasLimit property determines the maximum gas allowed. This helps in determining how many transactions can be part of the block.
• The gasUsed property refers to the actual gas used for this block for executing all transactions in it.
• The hash property refers to the hash of the block.
• The nonce property refers to the number that helps in solving the challenge.
• The miner property is the account identifier of the miner, also known as coinbase or etherbase.
• The number property is the sequential number of this block on the chain.
• The parentHash property refers to the parent block's hash.
• The receiptsRoot, stateRoot, and transactionsRoot properties refer to the Merkle trees discussed during the mining process.
• The transactions property refers to an array of transactions that are part of this block.
• The totalDifficulty property refers to the total difficulty of the chain.