**Currency**

Like solidity supports ETH, TRON VM supports trx and sun, 1 trx = 1000000 sun, case sensitive, only support lower case. Tron-IDE supports trx and sun, remix does not support trx and sun. We recommend to use Tron-IDE instead of remix to build TRON smart contract.

**Block**

• block.blockhash (uint blockNumber) returns (bytes32): specified block hash, can only apply to the latest 256 blocks and current block excluded

• block.coinbase (address): SuperNode address that produced the current block

• block.difficulty (uint): current block difficulty, not recommended, set 0

• block.gaslimit (uint): current block gas limit, not supported, set 0

• block.number (uint): current block number

• block.timestamp (uint): current block timestamp

• gasleft() returns (uint256): remaining gas

• msg.data (bytes): complete call data

• msg.gas (uint): remaining gas - since 0.4.21, not recommended, replaced by gesleft()

• msg.sender (address): message sender (current call)

• msg.sig (bytes4): first 4 bytes of call data (function identifier)

• msg.value (uint): the amount of SUN send with message

• now (uint): current block timestamp (block.timestamp)

• tx.gasprice (uint): the gas price of transaction, not recommended, set 0

• tx.origin (address): transaction initiator Each command of smart contract consume system resource while running, we use 'Energy' as the unit of the consumption of the resource.