There are special variables and functions that always exist globally. They are discussed in the upcoming sections.
The block and transaction properties are as follows:
block.blockhash(uint blockNumber) returns (bytes32): The hash of the given block only works for the 256 most recent blocks.block.coinbase (address): The current block miner's address.block.difficulty (uint): The current block difficulty.block.gaslimit (uint): The current block gas limit. It defines the maximum amount of gas that all transactions in the whole block combined are allowed to consume. Its purpose is to keep the block propagation and processing time low, thereby allowing a sufficiently decentralized network. Miners have the right to set the gas limit for the current block to be within ~0.0975% (1/1,024) of the gas limit of the last block, so the resulting gas limit should be the median of miners' preferences.block.number (uint): The current block number...