Basic Structure of a Solidity Contract

// SPDX-License-Identifier: MITpragma solidity ^0.8.0;contract MyContract {    // State variables    uint public myNumber;    // Constructor    constructor(uint _num) {        myNumber = _num;    }    // Function to update state variable    function setNumber(uint _num) public {        myNumber = _num;    }    // Function to retrieve state variable    function getNumber() public view returns (uint) {        return myNumber;    }}

Contract Structure

**Contracts **are the fundamental building blocks in Solidity, similar to classes in object-oriented programming.

1. State VariablesPermanently stored in contract storage, state variables represent the contract's state.
2. FunctionsFunctions are executable units of code within a contract.
3. EventsEvents allow logging to the Ethereum blockchain for frontend applications.

Data Types in Solidity
Value Types

1. bool: true or false
2. int/uint: signed and unsigned integers3.** address**: Ethereum address

3. bytes: dynamic array of bytes
   Reference Types

4. arrays: fixed or dynamic size

5. struct: custom defined type

6. mapping: hash tables

Function Visibility and Modifiers

Visibility Modifiers

1. public - Accessible from anywhere.Can be called internally or via messages. Generates a getter function for state variables.
2. private - Only within the contract.Only visible for the contract they are defined in.3.** internal** - Within the contract and derived contracts.Only accessible internally and by derived contracts.
3. *external *- Only callable from outside the contract.Can be called from other contracts and transactions. Cannot be called internally.

Function Modifiers

1. pure - No state modifications
2. view - Reads state but doesn’t modify it
3. payable - Accepts Ether

Gas Optimization Techniques

1. Use uint256Prefer uint256 for integers when possible.
2. Avoid LoopsMinimize loops to reduce gas consumption.
3. Use EventsEmit events instead of storing data.
4. Optimize StoragePack variables to save storage slots