In the previous chapter, we discussed Solidity—the programming language introduced by the Ethereum foundation. Solidity is the language that makes it possible to create decentralized applications on top of Ethereum blockchain, either to be used for creating another cryptocurrency token or for any other use case in which blockchain can have an essential role. 

Ethereum runs smart contracts on its platform; these are applications that use blockchain technology to perform the required action, enabling users to create their own blockchain and also issue their own alternative cryptocurrency. This is made possible by coding in Solidity, which is a contract-oriented programming language used for writing smart contracts that are to be executed on the Ethereum blockchain and perform the programmed tasks.

Solidity is a statically typed programming language that runs on the Ethereum virtual machine. It is influenced by C++, Python, and JavaScript, was proposed in August 2014 and developed by the Ethereum project's solidity team. The complete application is deployed on the blockchain, including smart contract, frontend interface, and other modules; this is known as a DApp or a Decentralized Application.

We will be covering the following topics in this chapter:

• Basics of solidity
• Layout of a Solidity file
• Structure of a smart contract
• Variables and functions
• Value types
• Reference types
• Key to value mapping