Compiling Smart Contracts

Compiling a smart contract involves using the contract's source code to generate its bytecode and the contract Application Binary Interface (ABI). The Ethereum Virtual Machine (EVM) executes the bytecode to understand and execute the smart contract. Meanwhile, other smart contracts use the ABI to understand how to interact with the deployed contracts on the Hedera network.

Compiling Solidity

The compiler for the Solidity programming language is solc (Solidity Compiler). You can use the compiler directly or embedded in IDEs like Remix IDE or tools like Hardhat and Truffle.

---

Smart Contract Bytecode

Bytecode is the machine-readable language that the EVM uses to execute smart contracts. The compiler analyzes the code, checks for syntax errors, enforces language-specific rules, and generates the corresponding bytecode.

Example:

This is the example bytecode output, produced in hexadecimal format, when the HelloHedera smart contract source code is compiled.

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

---

Smart Contract Application Binary Interface (ABI)

The ABI is a JSON (JavaScript Object Notation) file that represents the interface definition for the smart contract. It specifies function signatures, input parameters, return types, and other relevant details of the contract's interface. The ABI helps developers understand how to interact with the smart contract in their distributed applications.

Example:

This is the example ABI output produced when the HelloHedera smart contract is compiled.

"abi": [
    {
      "inputs": [
        {
          "internalType": "string",
          "name": "message_",
          "type": "string"
        }
      ],
      "stateMutability": "nonpayable",
      "type": "constructor"
    },
    {
      "inputs": [],
      "name": "get_message",
      "outputs": [
        {
          "internalType": "string",
          "name": "",
          "type": "string"
        }
      ],
      "stateMutability": "view",
      "type": "function"
    },
    {
      "inputs": [
        {
          "internalType": "string",
          "name": "message_",
          "type": "string"
        }
      ],
      "name": "set_message",
      "outputs": [],
      "stateMutability": "nonpayable",
      "type": "function"
    }
  ]
}

Additional Resources:

• Ethereum: Compiling Smart Contracts

---

System Smart Contracts

System smart contracts are Hedera API functionality logic presented at reserved address locations on the EVM network. These addresses contain reserved function selectors. When a deployed contract calls these selectors, they execute as though a corresponding system contract exists on the network. Both system and user-deployed contracts live at the same address. If a contract is redeployed, it gets a new address while the original address retains the old bytecode.

System Smart Contract Interfaces

Solidity interfaces provide and define a set of functions that other smart contracts can call. The interfaces for all Hedera systems contracts written in Solidity are maintained in the hedera-smart-contracts repository.

Note: The following Solidity examples are not production-ready and are intended solely for instructional purposes to guide developers.

The following is a list of available system contracts on Hedera:

➡ Exchange Rate

The exchange rate contract allows you to convert from tinycents to tinybars and from tinybars to tinycents.

Contract Address	Source
0x168	https://github.com/hashgraph/hedera-smart-contracts/tree/main/contracts/exchange-rate-precompile

Example ⬇

IExchangeRate.sol

// SPDX-License-Identifier: Apache-2.0
pragma solidity >=0.4.9 <0.9.0;

interface IExchangeRate {
    // Given a value in tinycents (1e-8 US cents or 1e-10 USD), returns the 
    // equivalent value in tinybars (1e-8 HBAR) at the current exchange rate 
    // stored in system file 0.0.112. 
    // 
    // This rate is a weighted median of the the recent" HBAR-USD exchange 
    // rate on major exchanges, but should _not_ be treated as a live price 
    // oracle! It is important primarily because the network will use it to 
    // compute the tinybar fees for the active transaction. 
    // 
    // So a "self-funding" contract can use this rate to compute how much 
    // tinybar its users must send to cover the Hedera fees for the transaction.
    function tinycentsToTinybars(uint256 tinycents) external returns (uint256);

    // Given a value in tinybars (1e-8 HBAR), returns the equivalent value in 
    // tinycents (1e-8 US cents or 1e-10 USD) at the current exchange rate 
    // stored in system file 0.0.112. 
    // 
    // This rate tracks the the HBAR-USD rate on public exchanges, but 
    // should _not_ be treated as a live price oracle! This conversion is
    // less likely to be needed than the above conversion from tinycent to
    // tinybars, but we include it for completeness.
    function tinybarsToTinycents(uint256 tinybars) external returns (uint256);
}

Reference: HIP-475.

➡ Hedera Token Service

The Hedera Token Service smart contract precompile provides functions to use the native Hedera Token Service in smart contracts. Tokens created using this method can also manage the tokens using the native Hedera Token Service APIs.

Contract Address	Source
0x167	https://github.com/hashgraph/hedera-smart-contracts/tree/main/contracts/hts-precompile

Example ⬇

IHederaTokenService.sol

// SPDX-License-Identifier: Apache-2.0
pragma solidity >=0.4.9 <0.9.0;
pragma experimental ABIEncoderV2;

interface IHederaTokenService {

    /// Transfers cryptocurrency among two or more accounts by making the desired adjustments to their
    /// balances. Each transfer list can specify up to 10 adjustments. Each negative amount is withdrawn
    /// from the corresponding account (a sender), and each positive one is added to the corresponding
    /// account (a receiver). The amounts list must sum to zero. Each amount is a number of tinybars
    /// (there are 100,000,000 tinybars in one hbar).  If any sender account fails to have sufficient
    /// hbars, then the entire transaction fails, and none of those transfers occur, though the
    /// transaction fee is still charged. This transaction must be signed by the keys for all the sending
    /// accounts, and for any receiving accounts that have receiverSigRequired == true. The signatures
    /// are in the same order as the accounts, skipping those accounts that don't need a signature.
    /// @custom:version 0.3.0 previous version did not include isApproval
    struct AccountAmount {
        // The Account ID, as a solidity address, that sends/receives cryptocurrency or tokens
        address accountID;

        // The amount of  the lowest denomination of the given token that
        // the account sends(negative) or receives(positive)
        int64 amount;

        // If true then the transfer is expected to be an approved allowance and the
        // accountID is expected to be the owner. The default is false (omitted).
        bool isApproval;
    }

    /// A sender account, a receiver account, and the serial number of an NFT of a Token with
    /// NON_FUNGIBLE_UNIQUE type. When minting NFTs the sender will be the default AccountID instance
    /// (0.0.0 aka 0x0) and when burning NFTs, the receiver will be the default AccountID instance.
    /// @custom:version 0.3.0 previous version did not include isApproval
    struct NftTransfer {
        // The solidity address of the sender
        address senderAccountID;

        // The solidity address of the receiver
        address receiverAccountID;

        // The serial number of the NFT
        int64 serialNumber;

        // If true then the transfer is expected to be an approved allowance and the
        // accountID is expected to be the owner. The default is false (omitted).
        bool isApproval;
    }

    struct TokenTransferList {
        // The ID of the token as a solidity address
        address token;

        // Applicable to tokens of type FUNGIBLE_COMMON. Multiple list of AccountAmounts, each of which
        // has an account and amount.
        AccountAmount[] transfers;

        // Applicable to tokens of type NON_FUNGIBLE_UNIQUE. Multiple list of NftTransfers, each of
        // which has a sender and receiver account, including the serial number of the NFT
        NftTransfer[] nftTransfers;
    }

    struct TransferList {
        // Multiple list of AccountAmounts, each of which has an account and amount.
        // Used to transfer hbars between the accounts in the list.
        AccountAmount[] transfers;
    }

    /// Expiry properties of a Hedera token - second, autoRenewAccount, autoRenewPeriod
    struct Expiry {
        // The epoch second at which the token should expire; if an auto-renew account and period are
        // specified, this is coerced to the current epoch second plus the autoRenewPeriod
        int64 second;

        // ID of an account which will be automatically charged to renew the token's expiration, at
        // autoRenewPeriod interval, expressed as a solidity address
        address autoRenewAccount;

        // The interval at which the auto-renew account will be charged to extend the token's expiry
        int64 autoRenewPeriod;
    }

    /// A Key can be a public key from either the Ed25519 or ECDSA(secp256k1) signature schemes, where
    /// in the ECDSA(secp256k1) case we require the 33-byte compressed form of the public key. We call
    /// these public keys <b>primitive keys</b>.
    /// A Key can also be the ID of a smart contract instance, which is then authorized to perform any
    /// precompiled contract action that requires this key to sign.
    /// Note that when a Key is a smart contract ID, it <i>doesn't</i> mean the contract with that ID
    /// will actually create a cryptographic signature. It only means that when the contract calls a
    /// precompiled contract, the resulting "child transaction" will be authorized to perform any action
    /// controlled by the Key.
    /// Exactly one of the possible values should be populated in order for the Key to be valid.
    struct KeyValue {

        // if set to true, the key of the calling Hedera account will be inherited as the token key
        bool inheritAccountKey;

        // smart contract instance that is authorized as if it had signed with a key
        address contractId;

        // Ed25519 public key bytes
        bytes ed25519;

        // Compressed ECDSA(secp256k1) public key bytes
        bytes ECDSA_secp256k1;

        // A smart contract that, if the recipient of the active message frame, should be treated
        // as having signed. (Note this does not mean the <i>code being executed in the frame</i>
        // will belong to the given contract, since it could be running another contract's code via
        // <tt>delegatecall</tt>. So setting this key is a more permissive version of setting the
        // contractID key, which also requires the code in the active message frame belong to the
        // the contract with the given id.)
        address delegatableContractId;
    }

    /// A list of token key types the key should be applied to and the value of the key
    struct TokenKey {

        // bit field representing the key type. Keys of all types that have corresponding bits set to 1
        // will be created for the token.
        // 0th bit: adminKey
        // 1st bit: kycKey
        // 2nd bit: freezeKey
        // 3rd bit: wipeKey
        // 4th bit: supplyKey
        // 5th bit: feeScheduleKey
        // 6th bit: pauseKey
        // 7th bit: ignored
        uint keyType;

        // the value that will be set to the key type
        KeyValue key;
    }

    /// Basic properties of a Hedera Token - name, symbol, memo, tokenSupplyType, maxSupply,
    /// treasury, freezeDefault. These properties are related both to Fungible and NFT token types.
    struct HederaToken {
        // The publicly visible name of the token. The token name is specified as a Unicode string.
        // Its UTF-8 encoding cannot exceed 100 bytes, and cannot contain the 0 byte (NUL).
        string name;

        // The publicly visible token symbol. The token symbol is specified as a Unicode string.
        // Its UTF-8 encoding cannot exceed 100 bytes, and cannot contain the 0 byte (NUL).
        string symbol;

        // The ID of the account which will act as a treasury for the token as a solidity address.
        // This account will receive the specified initial supply or the newly minted NFTs in
        // the case for NON_FUNGIBLE_UNIQUE Type
        address treasury;

        // The memo associated with the token (UTF-8 encoding max 100 bytes)
        string memo;

        // IWA compatibility. Specified the token supply type. Defaults to INFINITE
        bool tokenSupplyType;

        // IWA Compatibility. Depends on TokenSupplyType. For tokens of type FUNGIBLE_COMMON - the
        // maximum number of tokens that can be in circulation. For tokens of type NON_FUNGIBLE_UNIQUE -
        // the maximum number of NFTs (serial numbers) that can be minted. This field can never be changed!
        int64 maxSupply;

        // The default Freeze status (frozen or unfrozen) of Hedera accounts relative to this token. If
        // true, an account must be unfrozen before it can receive the token
        bool freezeDefault;

        // list of keys to set to the token
        TokenKey[] tokenKeys;

        // expiry properties of a Hedera token - second, autoRenewAccount, autoRenewPeriod
        Expiry expiry;
    }

    /// Additional post creation fungible and non fungible properties of a Hedera Token.
    struct TokenInfo {
        /// Basic properties of a Hedera Token
        HederaToken token;

        /// The number of tokens (fungible) or serials (non-fungible) of the token
        int64 totalSupply;

        /// Specifies whether the token is deleted or not
        bool deleted;

        /// Specifies whether the token kyc was defaulted with KycNotApplicable (true) or Revoked (false)
        bool defaultKycStatus;

        /// Specifies whether the token is currently paused or not
        bool pauseStatus;

        /// The fixed fees collected when transferring the token
        FixedFee[] fixedFees;

        /// The fractional fees collected when transferring the token
        FractionalFee[] fractionalFees;

        /// The royalty fees collected when transferring the token
        RoyaltyFee[] royaltyFees;

        /// The ID of the network ledger
        string ledgerId;
    }

    /// Additional fungible properties of a Hedera Token.
    struct FungibleTokenInfo {
        /// The shared hedera token info
        TokenInfo tokenInfo;

        /// The number of decimal places a token is divisible by
        int32 decimals;
    }

    /// Additional non fungible properties of a Hedera Token.
    struct NonFungibleTokenInfo {
        /// The shared hedera token info
        TokenInfo tokenInfo;

        /// The serial number of the nft
        int64 serialNumber;

        /// The account id specifying the owner of the non fungible token
        address ownerId;

        /// The epoch second at which the token was created.
        int64 creationTime;

        /// The unique metadata of the NFT
        bytes metadata;

        /// The account id specifying an account that has been granted spending permissions on this nft
        address spenderId;
    }

    /// A fixed number of units (hbar or token) to assess as a fee during a transfer of
    /// units of the token to which this fixed fee is attached. The denomination of
    /// the fee depends on the values of tokenId, useHbarsForPayment and
    /// useCurrentTokenForPayment. Exactly one of the values should be set.
    struct FixedFee {

        int64 amount;

        // Specifies ID of token that should be used for fixed fee denomination
        address tokenId;

        // Specifies this fixed fee should be denominated in Hbar
        bool useHbarsForPayment;

        // Specifies this fixed fee should be denominated in the Token currently being created
        bool useCurrentTokenForPayment;

        // The ID of the account to receive the custom fee, expressed as a solidity address
        address feeCollector;
    }

    /// A fraction of the transferred units of a token to assess as a fee. The amount assessed will never
    /// be less than the given minimumAmount, and never greater than the given maximumAmount.  The
    /// denomination is always units of the token to which this fractional fee is attached.
    struct FractionalFee {
        // A rational number's numerator, used to set the amount of a value transfer to collect as a custom fee
        int64 numerator;

        // A rational number's denominator, used to set the amount of a value transfer to collect as a custom fee
        int64 denominator;

        // The minimum amount to assess
        int64 minimumAmount;

        // The maximum amount to assess (zero implies no maximum)
        int64 maximumAmount;
        bool netOfTransfers;

        // The ID of the account to receive the custom fee, expressed as a solidity address
        address feeCollector;
    }

    /// A fee to assess during a transfer that changes ownership of an NFT. Defines the fraction of
    /// the fungible value exchanged for an NFT that the ledger should collect as a royalty. ("Fungible
    /// value" includes both ℏ and units of fungible HTS tokens.) When the NFT sender does not receive
    /// any fungible value, the ledger will assess the fallback fee, if present, to the new NFT owner.
    /// Royalty fees can only be added to tokens of type type NON_FUNGIBLE_UNIQUE.
    struct RoyaltyFee {
        // A fraction's numerator of fungible value exchanged for an NFT to collect as royalty
        int64 numerator;

        // A fraction's denominator of fungible value exchanged for an NFT to collect as royalty
        int64 denominator;

        // If present, the fee to assess to the NFT receiver when no fungible value
        // is exchanged with the sender. Consists of:
        // amount: the amount to charge for the fee
        // tokenId: Specifies ID of token that should be used for fixed fee denomination
        // useHbarsForPayment: Specifies this fee should be denominated in Hbar
        int64 amount;
        address tokenId;
        bool useHbarsForPayment;

        // The ID of the account to receive the custom fee, expressed as a solidity address
        address feeCollector;
    }

    /**********************
     * Direct HTS Calls   *
     **********************/

    /// Performs transfers among combinations of tokens and hbars
    /// @param transferList the list of hbar transfers to do
    /// @param tokenTransfers the list of token transfers to do
    /// @custom:version 0.3.0 the signature of the previous version was cryptoTransfer(TokenTransferList[] memory tokenTransfers)
    function cryptoTransfer(TransferList memory transferList, TokenTransferList[] memory tokenTransfers)
        external
        returns (int64 responseCode);

    /// Mints an amount of the token to the defined treasury account
    /// @param token The token for which to mint tokens. If token does not exist, transaction results in
    ///              INVALID_TOKEN_ID
    /// @param amount Applicable to tokens of type FUNGIBLE_COMMON. The amount to mint to the Treasury Account.
    ///               Amount must be a positive non-zero number represented in the lowest denomination of the
    ///               token. The new supply must be lower than 2^63.
    /// @param metadata Applicable to tokens of type NON_FUNGIBLE_UNIQUE. A list of metadata that are being created.
    ///                 Maximum allowed size of each metadata is 100 bytes
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return newTotalSupply The new supply of tokens. For NFTs it is the total count of NFTs
    /// @return serialNumbers If the token is an NFT the newly generate serial numbers, othersise empty.
    function mintToken(
        address token,
        int64 amount,
        bytes[] memory metadata
    )
        external
        returns (
            int64 responseCode,
            int64 newTotalSupply,
            int64[] memory serialNumbers
        );

    /// Burns an amount of the token from the defined treasury account
    /// @param token The token for which to burn tokens. If token does not exist, transaction results in
    ///              INVALID_TOKEN_ID
    /// @param amount  Applicable to tokens of type FUNGIBLE_COMMON. The amount to burn from the Treasury Account.
    ///                Amount must be a positive non-zero number, not bigger than the token balance of the treasury
    ///                account (0; balance], represented in the lowest denomination.
    /// @param serialNumbers Applicable to tokens of type NON_FUNGIBLE_UNIQUE. The list of serial numbers to be burned.
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return newTotalSupply The new supply of tokens. For NFTs it is the total count of NFTs
    function burnToken(
        address token,
        int64 amount,
        int64[] memory serialNumbers
    ) external returns (int64 responseCode, int64 newTotalSupply);

    ///  Associates the provided account with the provided tokens. Must be signed by the provided
    ///  Account's key or called from the accounts contract key
    ///  If the provided account is not found, the transaction will resolve to INVALID_ACCOUNT_ID.
    ///  If the provided account has been deleted, the transaction will resolve to ACCOUNT_DELETED.
    ///  If any of the provided tokens is not found, the transaction will resolve to INVALID_TOKEN_REF.
    ///  If any of the provided tokens has been deleted, the transaction will resolve to TOKEN_WAS_DELETED.
    ///  If an association between the provided account and any of the tokens already exists, the
    ///  transaction will resolve to TOKEN_ALREADY_ASSOCIATED_TO_ACCOUNT.
    ///  If the provided account's associations count exceed the constraint of maximum token associations
    ///    per account, the transaction will resolve to TOKENS_PER_ACCOUNT_LIMIT_EXCEEDED.
    ///  On success, associations between the provided account and tokens are made and the account is
    ///    ready to interact with the tokens.
    /// @param account The account to be associated with the provided tokens
    /// @param tokens The tokens to be associated with the provided account. In the case of NON_FUNGIBLE_UNIQUE
    ///               Type, once an account is associated, it can hold any number of NFTs (serial numbers) of that
    ///               token type
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function associateTokens(address account, address[] memory tokens)
        external
        returns (int64 responseCode);

    /// Single-token variant of associateTokens. Will be mapped to a single entry array call of associateTokens
    /// @param account The account to be associated with the provided token
    /// @param token The token to be associated with the provided account
    function associateToken(address account, address token)
        external
        returns (int64 responseCode);

    /// Dissociates the provided account with the provided tokens. Must be signed by the provided
    /// Account's key.
    /// If the provided account is not found, the transaction will resolve to INVALID_ACCOUNT_ID.
    /// If the provided account has been deleted, the transaction will resolve to ACCOUNT_DELETED.
    /// If any of the provided tokens is not found, the transaction will resolve to INVALID_TOKEN_REF.
    /// If any of the provided tokens has been deleted, the transaction will resolve to TOKEN_WAS_DELETED.
    /// If an association between the provided account and any of the tokens does not exist, the
    /// transaction will resolve to TOKEN_NOT_ASSOCIATED_TO_ACCOUNT.
    /// If a token has not been deleted and has not expired, and the user has a nonzero balance, the
    /// transaction will resolve to TRANSACTION_REQUIRES_ZERO_TOKEN_BALANCES.
    /// If a <b>fungible token</b> has expired, the user can disassociate even if their token balance is
    /// not zero.
    /// If a <b>non fungible token</b> has expired, the user can <b>not</b> disassociate if their token
    /// balance is not zero. The transaction will resolve to TRANSACTION_REQUIRED_ZERO_TOKEN_BALANCES.
    /// On success, associations between the provided account and tokens are removed.
    /// @param account The account to be dissociated from the provided tokens
    /// @param tokens The tokens to be dissociated from the provided account.
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function dissociateTokens(address account, address[] memory tokens)
        external
        returns (int64 responseCode);

    /// Single-token variant of dissociateTokens. Will be mapped to a single entry array call of dissociateTokens
    /// @param account The account to be associated with the provided token
    /// @param token The token to be associated with the provided account
    function dissociateToken(address account, address token)
        external
        returns (int64 responseCode);

    /// Creates a Fungible Token with the specified properties
    /// @param token the basic properties of the token being created
    /// @param initialTotalSupply Specifies the initial supply of tokens to be put in circulation. The
    /// initial supply is sent to the Treasury Account. The supply is in the lowest denomination possible.
    /// @param decimals the number of decimal places a token is divisible by
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return tokenAddress the created token's address
    function createFungibleToken(
        HederaToken memory token,
        int64 initialTotalSupply,
        int32 decimals
    ) external payable returns (int64 responseCode, address tokenAddress);

    /// Creates a Fungible Token with the specified properties
    /// @param token the basic properties of the token being created
    /// @param initialTotalSupply Specifies the initial supply of tokens to be put in circulation. The
    /// initial supply is sent to the Treasury Account. The supply is in the lowest denomination possible.
    /// @param decimals the number of decimal places a token is divisible by.
    /// @param fixedFees list of fixed fees to apply to the token
    /// @param fractionalFees list of fractional fees to apply to the token
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return tokenAddress the created token's address
    function createFungibleTokenWithCustomFees(
        HederaToken memory token,
        int64 initialTotalSupply,
        int32 decimals,
        FixedFee[] memory fixedFees,
        FractionalFee[] memory fractionalFees
    ) external payable returns (int64 responseCode, address tokenAddress);

    /// Creates an Non Fungible Unique Token with the specified properties
    /// @param token the basic properties of the token being created
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return tokenAddress the created token's address
    function createNonFungibleToken(HederaToken memory token)
        external
        payable
        returns (int64 responseCode, address tokenAddress);

    /// Creates an Non Fungible Unique Token with the specified properties
    /// @param token the basic properties of the token being created
    /// @param fixedFees list of fixed fees to apply to the token
    /// @param royaltyFees list of royalty fees to apply to the token
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return tokenAddress the created token's address
    function createNonFungibleTokenWithCustomFees(
        HederaToken memory token,
        FixedFee[] memory fixedFees,
        RoyaltyFee[] memory royaltyFees
    ) external payable returns (int64 responseCode, address tokenAddress);

    /**********************
     * ABIV1 calls        *
     **********************/

    /// Initiates a Fungible Token Transfer
    /// @param token The ID of the token as a solidity address
    /// @param accountId account to do a transfer to/from
    /// @param amount The amount from the accountId at the same index
    function transferTokens(
        address token,
        address[] memory accountId,
        int64[] memory amount
    ) external returns (int64 responseCode);

    /// Initiates a Non-Fungable Token Transfer
    /// @param token The ID of the token as a solidity address
    /// @param sender the sender of an nft
    /// @param receiver the receiver of the nft sent by the same index at sender
    /// @param serialNumber the serial number of the nft sent by the same index at sender
    function transferNFTs(
        address token,
        address[] memory sender,
        address[] memory receiver,
        int64[] memory serialNumber
    ) external returns (int64 responseCode);

    /// Transfers tokens where the calling account/contract is implicitly the first entry in the token transfer list,
    /// where the amount is the value needed to zero balance the transfers. Regular signing rules apply for sending
    /// (positive amount) or receiving (negative amount)
    /// @param token The token to transfer to/from
    /// @param sender The sender for the transaction
    /// @param recipient The receiver of the transaction
    /// @param amount Non-negative value to send. a negative value will result in a failure.
    function transferToken(
        address token,
        address sender,
        address recipient,
        int64 amount
    ) external returns (int64 responseCode);

    /// Transfers tokens where the calling account/contract is implicitly the first entry in the token transfer list,
    /// where the amount is the value needed to zero balance the transfers. Regular signing rules apply for sending
    /// (positive amount) or receiving (negative amount)
    /// @param token The token to transfer to/from
    /// @param sender The sender for the transaction
    /// @param recipient The receiver of the transaction
    /// @param serialNumber The serial number of the NFT to transfer.
    function transferNFT(
        address token,
        address sender,
        address recipient,
        int64 serialNumber
    ) external returns (int64 responseCode);

    /// Allows spender to withdraw from your account multiple times, up to the value amount. If this function is called
    /// again it overwrites the current allowance with value.
    /// Only Applicable to Fungible Tokens
    /// @param token The hedera token address to approve
    /// @param spender the account address authorized to spend
    /// @param amount the amount of tokens authorized to spend.
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function approve(
        address token,
        address spender,
        uint256 amount
    ) external returns (int64 responseCode);

    /// Transfers `amount` tokens from `from` to `to` using the
    //  allowance mechanism. `amount` is then deducted from the caller's allowance.
    /// Only applicable to fungible tokens
    /// @param token The address of the fungible Hedera token to transfer
    /// @param from The account address of the owner of the token, on the behalf of which to transfer `amount` tokens
    /// @param to The account address of the receiver of the `amount` tokens
    /// @param amount The amount of tokens to transfer from `from` to `to`
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function transferFrom(address token, address from, address to, uint256 amount) external returns (int64 responseCode);

    /// Returns the amount which spender is still allowed to withdraw from owner.
    /// Only Applicable to Fungible Tokens
    /// @param token The Hedera token address to check the allowance of
    /// @param owner the owner of the tokens to be spent
    /// @param spender the spender of the tokens
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return allowance The amount which spender is still allowed to withdraw from owner.
    function allowance(
        address token,
        address owner,
        address spender
    ) external returns (int64 responseCode, uint256 allowance);

    /// Allow or reaffirm the approved address to transfer an NFT the approved address does not own.
    /// Only Applicable to NFT Tokens
    /// @param token The Hedera NFT token address to approve
    /// @param approved The new approved NFT controller.  To revoke approvals pass in the zero address.
    /// @param serialNumber The NFT serial number  to approve
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function approveNFT(
        address token,
        address approved,
        uint256 serialNumber
    ) external returns (int64 responseCode);

    /// Transfers `serialNumber` of `token` from `from` to `to` using the allowance mechanism.
    /// Only applicable to NFT tokens
    /// @param token The address of the non-fungible Hedera token to transfer
    /// @param from The account address of the owner of `serialNumber` of `token`
    /// @param to The account address of the receiver of `serialNumber`
    /// @param serialNumber The NFT serial number to transfer
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function transferFromNFT(address token, address from, address to, uint256 serialNumber) external returns (int64 responseCode);

    /// Get the approved address for a single NFT
    /// Only Applicable to NFT Tokens
    /// @param token The Hedera NFT token address to check approval
    /// @param serialNumber The NFT to find the approved address for
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return approved The approved address for this NFT, or the zero address if there is none
    function getApproved(address token, uint256 serialNumber)
        external
        returns (int64 responseCode, address approved);

    /// Enable or disable approval for a third party ("operator") to manage
    ///  all of `msg.sender`'s assets
    /// @param token The Hedera NFT token address to approve
    /// @param operator Address to add to the set of authorized operators
    /// @param approved True if the operator is approved, false to revoke approval
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function setApprovalForAll(
        address token,
        address operator,
        bool approved
    ) external returns (int64 responseCode);

    /// Query if an address is an authorized operator for another address
    /// Only Applicable to NFT Tokens
    /// @param token The Hedera NFT token address to approve
    /// @param owner The address that owns the NFTs
    /// @param operator The address that acts on behalf of the owner
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return approved True if `operator` is an approved operator for `owner`, false otherwise
    function isApprovedForAll(
        address token,
        address owner,
        address operator
    ) external returns (int64 responseCode, bool approved);

    /// Query if token account is frozen
    /// @param token The token address to check
    /// @param account The account address associated with the token
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return frozen True if `account` is frozen for `token`
    function isFrozen(address token, address account)
        external
        returns (int64 responseCode, bool frozen);

    /// Query if token account has kyc granted
    /// @param token The token address to check
    /// @param account The account address associated with the token
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return kycGranted True if `account` has kyc granted for `token`
    function isKyc(address token, address account)
        external
        returns (int64 responseCode, bool kycGranted);

    /// Operation to delete token
    /// @param token The token address to be deleted
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function deleteToken(address token) external returns (int64 responseCode);

    /// Query token custom fees
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return fixedFees Set of fixed fees for `token`
    /// @return fractionalFees Set of fractional fees for `token`
    /// @return royaltyFees Set of royalty fees for `token`
    function getTokenCustomFees(address token)
        external
        returns (int64 responseCode, FixedFee[] memory fixedFees, FractionalFee[] memory fractionalFees, RoyaltyFee[] memory royaltyFees);

    /// Query token default freeze status
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return defaultFreezeStatus True if `token` default freeze status is frozen.
    function getTokenDefaultFreezeStatus(address token)
        external
        returns (int64 responseCode, bool defaultFreezeStatus);
    
    /// Query token default kyc status
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return defaultKycStatus True if `token` default kyc status is KycNotApplicable and false if Revoked.
    function getTokenDefaultKycStatus(address token)
        external
        returns (int64 responseCode, bool defaultKycStatus);

    /// Query token expiry info
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return expiry Expiry info for `token`
    function getTokenExpiryInfo(address token)
        external
        returns (int64 responseCode, Expiry memory expiry);

    /// Query fungible token info
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return fungibleTokenInfo FungibleTokenInfo info for `token`
    function getFungibleTokenInfo(address token)
        external
        returns (int64 responseCode, FungibleTokenInfo memory fungibleTokenInfo);

    /// Query token info
    /// @param token The token address to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return tokenInfo TokenInfo info for `token`
    function getTokenInfo(address token)
        external
        returns (int64 responseCode, TokenInfo memory tokenInfo);

    /// Query token KeyValue
    /// @param token The token address to check
    /// @param keyType The keyType of the desired KeyValue
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return key KeyValue info for key of type `keyType`
    function getTokenKey(address token, uint keyType)
        external
        returns (int64 responseCode, KeyValue memory key);

    /// Query non fungible token info
    /// @param token The token address to check
    /// @param serialNumber The NFT serialNumber to check
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return nonFungibleTokenInfo NonFungibleTokenInfo info for `token` `serialNumber`
    function getNonFungibleTokenInfo(address token, int64 serialNumber)
        external
        returns (int64 responseCode, NonFungibleTokenInfo memory nonFungibleTokenInfo);

    /// Operation to freeze token account
    /// @param token The token address
    /// @param account The account address to be frozen
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function freezeToken(address token, address account)
        external
        returns (int64 responseCode);

    /// Operation to unfreeze token account
    /// @param token The token address
    /// @param account The account address to be unfrozen
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function unfreezeToken(address token, address account)
        external
        returns (int64 responseCode);

    /// Operation to grant kyc to token account
    /// @param token The token address
    /// @param account The account address to grant kyc
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function grantTokenKyc(address token, address account)
        external
        returns (int64 responseCode);

    /// Operation to revoke kyc to token account
    /// @param token The token address
    /// @param account The account address to revoke kyc
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function revokeTokenKyc(address token, address account)
        external
        returns (int64 responseCode);

    /// Operation to pause token
    /// @param token The token address to be paused
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function pauseToken(address token) external returns (int64 responseCode);

    /// Operation to unpause token
    /// @param token The token address to be unpaused
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function unpauseToken(address token) external returns (int64 responseCode);

    /// Operation to wipe fungible tokens from account
    /// @param token The token address
    /// @param account The account address to revoke kyc
    /// @param amount The number of tokens to wipe
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function wipeTokenAccount(
        address token,
        address account,
        int64 amount
    ) external returns (int64 responseCode);

    /// Operation to wipe non fungible tokens from account
    /// @param token The token address
    /// @param account The account address to revoke kyc
    /// @param  serialNumbers The serial numbers of token to wipe
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function wipeTokenAccountNFT(
        address token,
        address account,
        int64[] memory serialNumbers
    ) external returns (int64 responseCode);

    /// Operation to update token info
    /// @param token The token address
    /// @param tokenInfo The hedera token info to update token with
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function updateTokenInfo(address token, HederaToken memory tokenInfo)
        external
        returns (int64 responseCode);

    /// Operation to update token expiry info
    /// @param token The token address
    /// @param expiryInfo The hedera token expiry info
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function updateTokenExpiryInfo(address token, Expiry memory expiryInfo)
        external
        returns (int64 responseCode);

    /// Operation to update token expiry info
    /// @param token The token address
    /// @param keys The token keys
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    function updateTokenKeys(address token, TokenKey[] memory keys)
        external
        returns (int64 responseCode);

    /// Query if valid token found for the given address
    /// @param token The token address
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.    
    /// @return isToken True if valid token found for the given address     
    function isToken(address token) 
        external returns 
        (int64 responseCode, bool isToken);

    /// Query to return the token type for a given address
    /// @param token The token address
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.    
    /// @return tokenType the token type. 0 is FUNGIBLE_COMMON, 1 is NON_FUNGIBLE_UNIQUE, -1 is UNRECOGNIZED   
    function getTokenType(address token)
        external returns 
        (int64 responseCode, int32 tokenType);

    /// Initiates a Redirect For Token
    /// @param token The token address
    /// @param encodedFunctionSelector The function selector from the ERC20 interface + the bytes input for the function called
    /// @return responseCode The response code for the status of the request. SUCCESS is 22.
    /// @return response The result of the call that had been encoded and sent for execution.
    function redirectForToken(address token, bytes memory encodedFunctionSelector) external returns (int64 responseCode, bytes memory response);
}

Reference: HIP-358, HIP-206, HIP-376, HIP-514.

➡ Pseudo Random Number Generator (PRNG)

The PRNG system contract allows you to generate a pseudo-random number that can be used in smart contracts.

Contract Address	Source
0x169	https://github.com/hashgraph/hedera-smart-contracts/tree/main/contracts/util-precompile

Example ⬇

IPrngSystemContract.sol

// SPDX-License-Identifier: Apache-2.0
pragma solidity >=0.4.9 <0.9.0;

interface IPrngSystemContract {
    // Generates a 256-bit pseudorandom seed using the first 256-bits of running hash of n-3 transaction record.
    // Users can generate a pseudorandom number in a specified range using the seed by (integer value of seed % range)
    function getPseudorandomSeed() external returns (bytes32);
}

Reference: HIP-351.

---

Compiling Smart Contract Example

• Hardhat