CH2. Solidity data types: information stored in a variable, such as a specific value or a reference address of a memory location. Solidity data types can be categorized into value types and reference types.

Value types: These store data within a defined memory space. Changes to a copied value type will not alter the original value type.

Value Type Description Example/Details
Signed Integers Stores positive and negative whole numbers. Size options: int8, int16, ..., int256 (increments of 8 bits, max size: 256 bits)
Unsigned Integers Stores only non-negative whole numbers. Size options: uint8, uint16, ..., uint256 (increments of 8 bits, max size: 256 bits)
Booleans Represents true or false values. bool: true or false
Addresses(address_ Stores Ethereum addresses (20 bytes or 160 bits). 1. address : basic address type
  1. address payable: supports transfer and send for ETH transfers | | Fixed-size Byte Arrays | Arrays of fixed byte size. | Declared as bytes1, bytes2, ..., bytes32 (up to 32 bytes max) | | Enums | User-defined data type to represent a set of named constants. Improves readability and maintainability for smart contract | Example: enum Status { Active, Inactive, Suspended } |

CH3. Function

Syntax

function functionName(parameter1Type parameter1Name, parameter2Type parameter2Name) visibility [modifiers] returns (returnType) {
    // function body
}

In Solidity, functions can be categorized based on their interaction with the blockchain state:

Description Example/Details
View Functions Can read state variables defined in the smart contract but can not modify them function getBalance() public view returns (uint) {
return balance;
}
Pure Functions Can’t read nor modify state variables defined in the contract. Mostly used for calculations only based on parameters. function add(uint256 a, uint256 b) public pure returns (uint256) {
return a + b;
}
Payable Functions can recieve ether, they are essential for financial transactions. function deposit() public payable {
balance += msg.value;
}

Function Visibility

Public Can be called internally and externally
Private Can only be called from within the current contract
Internal Can be called internally and by derived contracts
External Can only be called from outside the contract

CH4. returns: Specifies the output type(s) of the function

Description Example/Details
Basic Return Types Solidity functions can return simple data types like integers, booleans, addresses, and strings function getResult() public pure returns (uint) {
return 42;
}
Multiple Return Values Solidity allows functions to return multiple values function getMultipleValues() public pure returns (uint, bool, string memory) {
return (42, true, "Hello");
}
Named Return Variables In Solidity, if you name the return variables in the returns clause, you can assign values to them directly within the function body without an explicit return statement.
However, you can still use return (sum, product); if you prefer. function namedReturn() public pure returns (uint product, uint sum) { 
uint a = 5;
uint b = 3;
product = a * b;
sum = a + b;

} **No need to explicitly return since product and sum are assigned. |