Comments in Solidity

In Solidity, comments are used to add explanations or notes to the code, which are ignored by the compiler. There are two types of comments: single-line comments and multi-line comments.

Single-line comments: These comments start with // and continue until the end of the line. Anything following // on a line is ignored by the compiler. For example:

// This is a single-line comment

Multi-line comments: These comments start with /* and end with */. Anything between these two symbols is ignored by the compiler. For example:

/* This is a 
multi-line comment */

It's a good practice to use comments in the smart contract to explain the purpose of the contract and the different functions, also to explain any complex logic or specific details that may not be immediately obvious from the code.

Also, comments can be used to disable code by adding // at the beginning of the line, this is useful during testing or debugging.

It's important to keep in mind that comments do not affect the execution of the smart contract and do not take up any space in the blockchain, so they do not affect the gas cost of the contract.

NatSpec in Solidity

NatSpec (Natural Specification) is a documentation standard for smart contracts in Solidity that allows developers to add human-readable documentation to their smart contract functions. NatSpec is a way to provide additional information about the smart contract functions, such as their purpose, input and output parameters, and return values.

NatSpec documentation is added to the smart contract using special comments that start with /** and end with */. The comments should be placed immediately above the function or variable that they document.

Here is an example of NatSpec documentation for a smart contract function:

/**
 * @title My token
 * @dev This function mints a new token to the msg.sender
 * @param _to The address to mint the token to
 * @param _value The amount of tokens to mint
 * @return A bool that indicates if the minting was successful
 */
function mint(address _to, uint256 _value) public returns (bool) {
    // function code here
}

In this example, the NatSpec documentation provides information about the purpose of the function, its input parameters, and its return value.

NatSpec comments can also be used to add information about the contract's name, author, and other details.

NatSpec can be used with different tools to extract the documentation from the smart contract and generate a human-readable documentation, this makes it easy for the end-users of the smart contract to understand its functionality and use.

It's important to note that NatSpec comments are not executed by the EVM and do not affect the functionality of the smart contract, they are only used to provide additional information to the users.