## HTML Fund Me: Introduction to Function Selectors We'll look at function selectors and how they work within a smart contract. We can confirm or reject a transaction, and there is a lot of data visible within the MetaMask transaction window. If we go to the **DATA** tab, we see the function type is **Fund**. We can also see the raw transaction data in the **HEX** section of the transaction. We see the value, which is 0.1 GO or ethereum. We are going to explore function selectors in greater detail in a later lesson, but for now, we can see how they operate. We have a **Fund** function within our Solidity code. ```python function fund() public payable { require(msg.value.getConversionRate(priceFeed) >= MINIMUM_USD, "You need to spend more ETH!!" ); // addressToAmountFunded[msg.sender] += msg.value; s_funders.push(msg.sender); s_addressToAmountFunded[msg.sender] += msg.value; } ``` This function needs to be converted into a low-level byte code for ethereum to understand. This is where function selectors come in. We can see that the MetaMask transaction window shows us the function type is **Fund**. We can find the function selector ourselves by using a cast command. We run a cast command with a signature such as: ```bash cast sig "fund()" ``` The output for this command would be a function selector in Hex format, which is 0xb6e0d4288. The function signature **fund** returns the function selector. If we were to change the name of the function within our smart contract from **fund** to **stealMoney**, we can see that the function selector would be different. ```python function stealMoney() public payable { require(msg.value.getConversionRate(priceFeed) >= MINIMUM_USD, "You need to spend more ETH!!" ); // addressToAmountFunded[msg.sender] += msg.value; s_funders.push(msg.sender); s_addressToAmountFunded[msg.sender] += msg.value; } ``` We can check this in the terminal with the command: ```bash cast sig "stealMoney()" ``` The function selector for stealMoney() is 0xa7ea5e4e, different from the fund() selector. We'll explore function selectors and this methodology in greater depth later.