_Follow along the course with this video._ --- ### EVM Encoding What we've learnt so far is that any `EVM compatible` chain is looking for the `bytecode` of a transaction in order to understand how it's supposed to respond. We've learnt as well that the global functionality of `abi.encode`, `abi.encodePacked` and `abi.decode` can be used to convert almost any data into this `bytecode` format. What these two things combined mean is that we can encode our own function calls as data that we send to a contracts address. ::image{src='/foundry-nfts/20-evm-encoding/evm-encoding1.png' style='width: 100%; height: auto;'} If we view a function call on Etherscan, we can see the input data in a human readable form as well as its original form, which is the `bytecode` representing that function (`function selector`). ::image{src='/foundry-nfts/20-evm-encoding/evm-encoding2.png' style='width: 100%; height: auto;'} The ability to do this empowers us as developers to do a lot of cool low-level things like making arbitrary function calls. I've said previously that in order to send a transaction you're always going to need two things: 1. ABI 2. Contract Address Originally we were referring to the human-readable ABI. Human-readable ABI ```json [ { "inputs": [], "name": "multiEncode", "outputs": [ { "internalType": "bytes", "name": "", "type": "bytes" } ], "stateMutability": "pure", "type": "function" }, { "inputs": [], "name": "multiEncodePacked", "outputs": [ { "internalType": "bytes", "name": "", "type": "bytes" } ], "stateMutability": "pure", "type": "function" }, { "inputs": [], "name": "multiStringCastPacked", "outputs": [ { "internalType": "string", "name": "", "type": "string" } ], "stateMutability": "pure", "type": "function" } ] ``` We can also accomplish our goals with the `bytecode` version directly. All you _really_ need to send a function call is the name of a function and the input types. Two questions arise: **_How do we send transactions that call functions with just the data field populated?_** **_How do we populate the data field?_** We're going to answer these by leveraging additional low-level keywords offered by Solidity, `staticcall` and `call`. We've used call previously... if this code rings a bell: ```solidity function withdraw(address recentWinner) public { (bool success, ) = recentWinner.call{value: address(this).balance}(""); require(success, "Transfer Failed"); } ``` **call:** How we call functions to change the state of the blockchain **staticcall:** How we call view or pure functions > ❗ **PROTIP** > `send` and `delegatecall` also exist as options for low-level calling to the blockchain, but we'll go over these in greater detail later! When we write `recentWinner.call{value: address(this).balance}("");` we're directly updating the value property of the transaction we're sending. The parenthesis at the end of this call are where we provide our transaction data. - within `{}` we're able to pass specific fields of a transaction, like `value` - within `()` we can pass the data needed to call a specific function. ### Wrap Up Whew, this is heavy, but it's advanced. The power provided by low-level function calls cannot be overstated. Now that we have some understanding of how encoding can be using in sending transactions, let's take a step back in the next lesson to recap what we've gone over