interface ArbSys {
    /**
    * @notice Get internal version number identifying an ArbOS build
    * @return version number as int
     */
    function arbOSVersion() external pure returns (uint);

    function arbChainID() external view returns(uint);

    /**
    * @notice Get Arbitrum block number (distinct from L1 block number; Arbitrum genesis block has block number 0)
    * @return block number as int
     */ 
    function arbBlockNumber() external view returns (uint);

    /** 
    * @notice Send given amount of Eth to dest from sender.
    * This is a convenience function, which is equivalent to calling sendTxToL1 with empty calldataForL1.
    * @param destination recipient address on L1
    * @return unique identifier for this L2-to-L1 transaction.
    */
    function withdrawEth(address destination) external payable returns(uint);

    /** 
    * @notice Send a transaction to L1
    * @param destination recipient address on L1 
    * @param calldataForL1 (optional) calldata for L1 contract call
    * @return a unique identifier for this L2-to-L1 transaction.
    */
    function sendTxToL1(address destination, bytes calldata calldataForL1) external payable returns(uint);

    /** 
    * @notice get the number of transactions issued by the given external account or the account sequence number of the given contract
    * @param account target account
    * @return the number of transactions issued by the given external account or the account sequence number of the given contract
    */
    function getTransactionCount(address account) external view returns(uint256);

    /**  
    * @notice get the value of target L2 storage slot 
    * This function is only callable from address 0 to prevent contracts from being able to call it
    * @param account target account
    * @param index target index of storage slot 
    * @return stotage value for the given account at the given index
    */
    function getStorageAt(address account, uint256 index) external view returns (uint256);

    /**
    * @notice check if current call is coming from l1
    * @return true if the caller of this was called directly from L1
    */
    function isTopLevelCall() external view returns (bool);

    /**
     * @notice check if the caller (of this caller of this) is an aliased L1 contract address
     * @return true iff the caller's address is an alias for an L1 contract address
     */
    function wasMyCallersAddressAliased() external view returns (bool);

    /**
     * @notice return the address of the caller (of this caller of this), without applying L1 contract address aliasing
     * @return address of the caller's caller, without applying L1 contract address aliasing
     */
    function myCallersAddressWithoutAliasing() external view returns (address);

    /**
     * @notice map L1 sender contract address to its L2 alias
     * @param sender sender address
     * @param dest destination address
     * @return aliased sender address
     */
    function mapL1SenderContractAddressToL2Alias(address sender, address dest) external pure returns(address);

    /**
     * @notice get the caller's amount of available storage gas
     * @return amount of storage gas available to the caller
     */
    function getStorageGasAvailable() external returns(uint);

    event L2ToL1Transaction(address caller, address indexed destination, uint indexed uniqueId,
                            uint indexed batchNumber, uint indexInBatch,
                            uint arbBlockNum, uint ethBlockNum, uint timestamp,
                            uint callvalue, bytes data);
}
/**
 * @title Precompiled contract that exists in every Arbitrum chain at address(100), 0x0000000000000000000000000000000000000064. Exposes a variety of system-level functionality.
 */
function arbBlockNumber() external view returns (uint);

/**
 * @notice Get Arbitrum block number (distinct from L1 block number; Arbitrum genesis block has block number 0)
 * @return block number as int
 */