An Introduction to Solidity, the Language that Runs Ethereum


Solidity is an object-oriented, statically typed, high-level scripting language for implementing smart contracts, which are programs that govern the behaviour of accounts within the Ethereum state. Learn more about Solidity in this article.

Solidity is a contract-based, advanced programming language. Its syntax is very similar to that of scripting languages like JavaScript. It was built to run the Ethereum blockchain platform and was shaped by existing languages — C++, Python and JavaScript, and is primarily designed to allow smart contracts to be created in the network. Solidity is a statically typed scripting language that verifies and enforces the constraints at compile-time as opposed to run-time.

Solidity uses a vast number of programming concepts from other languages. For example, it has variables, string manipulation, classes, functions, arithmetic operations and so on. While in a language like C, a programmer would be likely to create some form of a function, like ‘int main’ and ‘main’, Solidity works with a ‘contract’ that is created in an analogous manner. The Solidity programming language looks surprisingly similar to C++, C#, or JavaScript. Python developers will note that in Solidity, variables need their type to be explicitly declared, along with other differences.

The origins of Solidity
Computer scientist Gavin Wood originally came up with the concept of the Solidity language. Wood served as the CTO at Ethereum for two years. His idea was taken forward by Christian Reitwiessner, who led a team of people to actually develop it.
A brief history is given below.

  • August 2014: The Solidity language is proposed by Gavin Wood.
  • October 2014: Solidity is adopted as a language by Monax, a rival platform.
  • August 2015: Solidity is officially released.

Is it worth learning Solidity?
While learning blockchain related skills can be highly valuable, one would probably need to become an expert first in at least one other programming language. If you feel confident in dedicating a few years of your life to learning Solidity, give it a try. It’s quite possible that you will have a reliable, stable career for years to come. In addition to Solidity, there is Serpent, which is based on Python. As Python is a very simple and easy-to-understand language, it may be easier to learn in the future. For now though, Solidity is king. A good understanding of it will be very useful when learning other smart contract languages in the future.

What is so special about it?
Solidity is the code behind Ethereum – one of the largest blockchain platforms in the world (the other being Bitcoin). Both do have similarities – like being blockchain platforms with built-in tokens. Bitcoin’s currency (Bitcoin) and Ethereum’s currency (Ether) are two of the most important and broadly traded cryptocurrencies available. That’s where the similarities end. The Bitcoin network was created as a peer-to-peer currency exchange. Bitcoin, as a token, was always intended to be a store of value – an asset. On the other hand, Ethereum was created as a way for people to move anything of value, efficiently, not just cryptocurrency. The token, Ether, was created as a way to pay for those dealings on the platform. Its role was meant to be the ‘oil for the network’, not an asset like Bitcoin.
Since it was too complex to deal with anything other than cryptocurrencies on the Bitcoin platform, the team at Ethereum created a new system. It required a computing language with far more flexibility than Bitcoin’s (largely written in C++); so the team wrote the language Solidity.

What you can do with Solidity
Solidity is the base of the Ethereum network. Without Solidity, there is no Ethereum. Here’s what you can do with the former:

1. The programming language gives developers the skill to create their own decentralised apps (dApps). A way to think about it is like the apps you get on your smartphone. You can download all types of applications from the app store, covering everything from games and fitness to banking. dApps are the same. The main dissimilarity is that they are open source. Just as apps in the Apple app store are built to run on iOS, dApps on Ethereum are built to run on Solidity.

2. Within dApps, there are pieces of code recognised as smart contracts. These assist people to swap money, shares, property and nearly anything of value when certain conditions are met. That eliminates the need for an expensive third party like a notary.

So, when can one use Solidity? What are the applications of this programming language?
Solidity is an advanced programming language that has made coding around blockchain platforms particularly easy. Being easy to learn and rather easy to use, Solidity’s many applications include the following.

Voting: In the real world, the voting process is vulnerable to many forms of fraud such as the manipulation of data, booth capturing, fake voters, the manipulation of voting machines, etc. To solve a few of these problems, we could make use of contracts for voting. Solidity can be used to plan the code, and with proper implementation, the process of voting will be smooth, transparent and automatic.

Crowdfunding: If done through contracts, crowdfunding can solve various problems related with commissions for third parties, issues related to managing data, etc. For crowdfunding, smart contracts can work out far better than non-trusted federal systems. These smart contracts can be developed using Solidity.

Blind auctions: Implementation of blind auctions using Solidity is quite simple on Ethereum. An open sale can be created, in which every person is aware of each other’s bid. Following this, a blind auction can be designed whereby it will not be possible for anyone to see others’ bids until the bidding process ends.
Here is an example of a Solidity program.

contract GavCoin
mapping(address=>uint) balances;
uint constant totalCoins = 100000000000;

/// Endows creator of contract with 1m GAV.
function GavCoin(){
balances[msg.sender] = totalCoins;

/// Send $((valueInmGAV / 1000).fixed(0,3)) GAV from the account of $(message.caller.address()), to an account accessible only by $(to.address()).
function send(address to, uint256 valueInmGAV) {
if (balances[msg.sender] >= valueInmGAV) {
balances[to] += valueInmGAV;
balances[msg.sender] -= valueInmGAV;

/// getter function for the balance
function balance(address who) constant returns (uint256 balanceInmGAV) {
balanceInmGAV = balances[who];


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