What Is Solidity and How Is It Used to Develop Smart Contracts?


Solidity has come a long way since it was first proposed in 2014 and later developed by Ethereum’s Solidity team. There are hundreds of thousands of developers who use the programming language to create blockchain-based services for a growing number of use cases.

This article explains what Solidity is and how it is used in the Ethereum ecosystem. This article is for you if you’re interested in learning more about the inner workings of this blockchain-based programming language.

What Is Solidity?

Solidity is an object-oriented, high-level programming language used to create smart contracts that automate transactions on the blockchain. After being proposed in 2014, the language was developed by contributors to the Ethereum project. The language is primarily used to create smart contracts on the Ethereum blockchain and create smart contracts on other blockchains.

Solidity is similar to one of the most common programming languages, JavaScript. It can be considered as a dialect of JavaScript. This means that if you understand JavaScript, it can be easy to pick up Solidity. Solidity also shares similar characteristics to the programming languages C++ and Python.

As a high-level language, Solidity does away with the need to type code in ones and zeros. It makes it much easier for humans to write programs in ways they find easier to understand, using a combination of letters and numbers.

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Solidity is statically typed, with support for inheritance, libraries, and complex user-defined types. As Solidity is statically typed, the user much specify each variable. Data types allow the compiler to check for the correct use of variables. Solidity data types are usually categorized as either value types or reference types.

The main difference between value types and reference types can be found in how they are assigned to a variable and stored in the EVM (Ethereum Virtual Machine). While changing the value in one variable of a value type does not affect the value in another variable, anybody referring to changed values in reference type variables may get updated values.

How Does Solidity Work?

The beauty of the Ethereum ecosystem is that so many different cryptocurrencies and decentralized applications can use it. Smart contracts make it possible for unique technologies to be made on Ethereum for all kinds of businesses and organizations.

Every year, the world spends billions of dollars on blockchain solutions. Many of these solutions are created using Solidity. Smart contracts built using Solidity can be thought of as a way to automate business and non-business processes between different people. This ensures that people making transactions on the blockchain do not have to worry about risks such as fraud or not being able to use the same currency.

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One of the key components that makes the execution of Solidity code possible is the EVM. The EVM is described as a virtual computer on the blockchain which turns people’s ideas into code that runs applications on the blockchain.

Under the hood, Solidity creates machine-level code that is executed on the EVM. A compiler is used to break down high-level human-readable code, which it turns into instructions that the processor reads. Different platforms provide free Solidity compilation, including the Remix online compiler and a downloaded command-like compiler on a PC.

EVM smart contracts have some limitations which need to be addressed. One of the most significant of these is the limited access to useful library functions for parsing JSON structures or floating-point arithmetic.

Public and Private Functions

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Public functions are similar to APIs that anyone in the world may access. Anybody can call them in their code. Public functions are designed, in many cases, for shared processes on a platform that all users utilize.

For example, a public function could be made to allow all users of a platform to check their account balance. One of the most common ways of exploiting smart contracts is through public functions.

Related: What Is a Blockchain and How Does it Work?

While smart contracts can be easy to write with Solidity, it is often very difficult to write them securely. For example, if the withdrawal function in a smart contract isn’t secure, an attacker can manipulate the vulnerable function to drain an account of funds.

An attacker could call on a withdrawal function to send money to a different account, using a loop that repeatedly repeats the withdrawal function.

Private functions are only callable from inside the contracts. They contain instructions that can only be executed after being called on by other functions, in a chain. This makes it harder for the code to be manipulated by malicious actors.

Standards and Code Logic

Different standards are emerging which determine how Solidity smart contracts are used to build applications on Ethereum. These standards are known as ERC (Ethereum Request for Comments) standards. The standards are based on a document that contains guidelines on the required functions and restrictions on how code should behave.

The ERC standards that determine how Solidity works include:

  • ERC20
  • ERC165
  • ERC721
  • ERC223
  • ERC621
  • ERC777
  • ERC827
  • ERC884
  • ERC865
  • ERC1155

There are different ways Solidity can be used to make smart contracts interact with each other. Solidity can also be used to make dedicated instructions on how data is stored in the smart contract. The logic and data in smart contracts can be separated using Solidity. Using substitute contracts, the logic of a contract can be changed to allow for this.


It is impossible to change the code of a smart contract after it has been written and compiled. This means that every line of code has to work as intended or else there could be serious risks of the code being exploited.

Related: How to Become a Blockchain Programmer and Start Making Big Bucks

As the Ethereum blockchain is immutable, it is impossible to change the data and logic that is written to it. A way to get around this is to use a proxy to point to another contract that contains actual business logic. This allows for bugs to be fixed while a new version of the contract is implemented.

Gas Costs

There are extra costs that are paid for using Solidity on the Ethereum mainnet. Some of the extra costs are based on the gas system on Ethereum, which requires payment to miners for securing the blockchain network so that code can run safely on it.

When writing smart contracts, it is important to remember that gas costs can determine how performant a smart contract is. As gas fees are paid for every storage slot used, actions executed with Solidity code cost gas. A smart contract that is expensive to run is unlikely to be used in the long term.

Gas optimization helps to reduce the cost of gas when the Solidity code is executed. Some of the most popular methods of gas optimization include the use of libraries and using fewer functions. Libraries are often used to save bytecode.

Instead of adding unnecessary bytecode to the smart contract, the logic can be put in libraries. This helps to keep the smart contract size small. By using fewer functions, less bytecode is needed, and the difficulty of auditing code is also reduced.

How Can Solidity Be Used in Ethereum?

Solidity is used to create smart contracts for fungible tokens and non-fungible tokens. Different standards are used to build non-fungible tokens and fungible tokens in the Ethereum ecosystem.

These allow for different types of use cases to be created for people who use the blockchain. Solidity enables people to use tokens and non-fungible tokens on Ethereum. From minting non-fungible tokens to adding them to yield farming pools for extra interest, different kinds of uses for tokens are made possible by Ethereum.

Decentralized Autonomous Organizations (DAOs) are also made possible by Solidity. A DAO, which is a new type of online organizational structure, is primarily written in Solidity. DAOs allow different people to come together as members on an online platform where they vote on the DAO’s key decisions.

Solidity makes it possible to automate processes within the DAO. Examples of process automation in DAOs include making votes for key decisions and the allocation of reputation to DAO members for their contributions to the group.

Defining Standards for Blockchains

Solidity is much more than a programming language. It is defining standards for the future of blockchain technology.

Thanks to the number of open-source developers working to improve the security and performance of Solidity, thousands of applications in the Ethereum ecosystem continue to depend on it for their applications to operate. As new standards are created for smart contracts in Ethereum, the language will become safer to use.


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