Learning Solidity

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Explain Smart contract

A smart contract is an agreement between two people or entities in the form of computer code programmed to execute automatically. The idea was proposed in the 1990s by Nick Szabo, a pioneer of modern computer science, who defined them as a set of virtual promises with associated protocols to enforce them.

Smart contracts are executed on blockchain, which means that the terms are stored in a distributed database and cannot be changed. Transactions are also processed on the blockchain, which automates payments and counterparties. Since the emergence of the digital currency Ethereum, the creation and execution of smart contracts has been simplified, as complex transactions can be programmed into the Ethereum protocol.

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Explain Solidity language

Solidity is an object-oriented programming language created specifically by the Ethereum Network team for constructing and designing smart contracts on Blockchain platforms.

• It's used to create smart contracts that implement business logic and generate a chain of transaction records in the blockchain system.

• It acts as a tool for creating machine-level code and compiling it on the "Ethereum Virtual Machine" (EVM).

• It has a lot of similarities with C and C++ and is pretty simple to learn and understand. For example, a “main” in C is equivalent to a “contract” in Solidity.

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Create by Example Creating a contract in solidity involves writing functions and deploying them to the blockchain. Here are some examples of how to create a contract in Solidity:

Simple Storage Contract This is a simple storage contract example that stores a single value:

pragma solidity ^0.4.17; 
contract SimpleStorage { 
	uint storedData; 
	
	function set(uint x) public { 
		storedData = x; 
	} 
	
	function get() public view returns (uint) { 
		return storedData; 
	}
}

Payable Contract This is an example of a payable contract that allows users to send ether to the contract. The contract then stores the amount of ether received.

pragma solidity ^0.4.17; 
contract Payable { 
	uint storedData; 
	
	function payable(uint x) public payable { 
		storedData = x; 
	} 
	
	function get() public view returns (uint) { 
		return storedData; 
	}
}

Token Contract This is an example of a token contract that allows users to transfer tokens between accounts.

pragma solidity ^0.4.17; 
contract Token { 
	mapping (address => uint) public balances; 
	
	function transfer(address _to, uint _value) public { 
		require(balances[msg.sender] >= _value); 
		balances[msg.sender] -= _value; 
		balances[_to] += _value; 
	}
}

By using these examples, you can get started creating your own contracts in Solidity.

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LESSONS
Smart Contract Language	Remix Id Tutorial
Write You First Contract	Solidity Data Type
Solidity Function	State variable
Local Variable	Global variable
View Keyword	Pure Keyword
Event Ticket Smart Contract	Constant Keyword
If Else Keyword	while loop
Do Wile Loop	For Loop
Required Error	Assert Error
Revert Error	Modifier
Constructor	Mapping
Array	Array Remove
Replace Array	Enum Solidity
Import Enum	Structs
Import Structs	Data Location
Solidity Events	Inheritance
Shadowing Effect	Super Keyword
Visibility Solidity	Interface Solidity
Payable	Sending ether solidity
fallback	Call Function
DelegateCall	Calling other Contract
Create Other Contract	Try and catch
Solidity Library	Solidity ABI Encoded
Solidity ABI Decoded	Keccak256
DAPP	. . .

In the next lesson, we'll go over Introducing Solidity language.