Learn Solidity - 10 Code Examples & CST Typing Practice Test

Solidity is a statically typed, contract-oriented programming language designed for building smart contracts on the Ethereum blockchain. It enables developers to write decentralized applications (dApps), manage digital assets, and automate trustless logic using a syntax inspired by JavaScript, C++, and Python.

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Solidity Counter Contract Solidity Simple Addition Solidity Factorial Solidity Fibonacci Sequence Solidity Max of Two Numbers Solidity Array Sum Solidity Even Numbers Filter Solidity String Concatenation Solidity Counter With Loop Simulation Solidity Conditional Increment

Learn SOLIDITY with Real Code Examples

Updated Nov 19, 2025

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Code Sample Descriptions

Solidity Counter Contract

pragma solidity ^0.8.0;

contract Counter {
    uint public count = 0;
    bool public isDark = false;

    function increment() public {
        count++;
    }

    function decrement() public {
        count--;
    }

    function reset() public {
        count = 0;
    }

    function toggleTheme() public {
        isDark = !isDark;
    }

    function getUI() public view returns (uint, bool) {
        return (count, isDark);
    }
}

Demonstrates a simple counter smart contract with theme toggle functionality simulated as a boolean.

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Solidity Simple Addition

pragma solidity ^0.8.0;

contract AddProgram {
    uint public a = 5;
    uint public b = 3;
    uint public sum;

    function calculate() public {
        sum = a + b;
    }
}

Adds two numbers and stores the result in a state variable.

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Solidity Factorial

pragma solidity ^0.8.0;

contract Factorial {
    uint public n = 5;
    uint public fact = 1;

    function calculate() public {
        fact = 1;
        for(uint i=1;i<=n;i++) {
        fact *= i;
        }
    }
}

Calculates factorial of a number using a loop.

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Solidity Fibonacci Sequence

pragma solidity ^0.8.0;

contract Fibonacci {
    uint[10] public fib;

    function generate() public {
        fib[0] = 0;
        fib[1] = 1;
        for(uint i=2;i<10;i++) {
        fib[i] = fib[i-1] + fib[i-2];
        }
    }
}

Generates first 10 Fibonacci numbers stored in an array.

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Solidity Max of Two Numbers

pragma solidity ^0.8.0;

contract MaxProgram {
    uint public a = 7;
    uint public b = 10;
    uint public max;

    function findMax() public {
        max = a > b ? a : b;
    }
}

Finds the maximum of two numbers.

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Solidity Array Sum

pragma solidity ^0.8.0;

contract ArraySum {
    uint[5] public nums = [1,2,3,4,5];
    uint public sum;

    function calculateSum() public {
        sum = 0;
        for(uint i=0;i<nums.length;i++) {
        sum += nums[i];
        }
    }
}

Sums elements of an array and stores in a state variable.

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Solidity Even Numbers Filter

pragma solidity ^0.8.0;

contract EvenNumbers {
    uint[10] public nums = [1,2,3,4,5,6,7,8,9,10];
    uint[] public evens;

    function filter() public {
        delete evens;
        for(uint i=0;i<nums.length;i++) {
        if(nums[i] % 2 == 0) {
        evens.push(nums[i]);
        }
        }
    }
}

Returns even numbers from an array.

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Solidity String Concatenation

pragma solidity ^0.8.0;

contract ConcatStrings {
    string public str1 = 'HELLO';
    string public str2 = 'WORLD';
    string public result;

    function concat() public {
        result = string(abi.encodePacked(str1, str2));
    }
}

Concatenates two strings and stores in a state variable.

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Solidity Counter With Loop Simulation

pragma solidity ^0.8.0;

contract LoopCounter {
    uint public count;

    function run() public {
        count = 1;
        while(count <= 5) {
        count++;
        }
    }
}

Counts from 1 to 5 using a loop and stores the final count.

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Solidity Conditional Increment

pragma solidity ^0.8.0;

contract ConditionalIncrement {
    uint public count = 3;

    function run() public {
        if(count < 5) {
        count++;
        }
    }
}

Increment counter only if it is less than 5.

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Frequently Asked Questions about Solidity

What is Solidity?

What are the primary use cases for Solidity?

Smart contract development. DeFi protocols (DEXs, lending, staking). NFT standards (ERC-721, ERC-1155). Token creation (ERC-20). DAO governance mechanisms. Permissioned enterprise blockchain apps

What are the strengths of Solidity?

Native support for Ethereum standards. Large community & ecosystem. Powerful for financial logic. Extensive tooling (Hardhat, Foundry, Truffle). Rich developer resources

What are the limitations of Solidity?

Security vulnerabilities are common. Gas-cost constraints. Upgradability complexity. Difficult debugging across chains. Blockchain immutability adds risk

How can I practice Solidity typing speed?

CodeSpeedTest offers 10+ real Solidity code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Solidity Counter Contract

pragma solidity ^0.8.0;

contract Counter {
    uint public count = 0;
    bool public isDark = false;

    function increment() public {
        count++;
    }

    function decrement() public {
        count--;
    }

    function reset() public {
        count = 0;
    }

    function toggleTheme() public {
        isDark = !isDark;
    }

    function getUI() public view returns (uint, bool) {
        return (count, isDark);
    }
}

Demonstrates a simple counter smart contract with theme toggle functionality simulated as a boolean.

Let’s Try →

Solidity Simple Addition

pragma solidity ^0.8.0;

contract AddProgram {
    uint public a = 5;
    uint public b = 3;
    uint public sum;

    function calculate() public {
        sum = a + b;
    }
}

Adds two numbers and stores the result in a state variable.

Let’s Try →

Solidity Factorial

pragma solidity ^0.8.0;

contract Factorial {
    uint public n = 5;
    uint public fact = 1;

    function calculate() public {
        fact = 1;
        for(uint i=1;i<=n;i++) {
        fact *= i;
        }
    }
}

Calculates factorial of a number using a loop.

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Solidity Fibonacci Sequence

pragma solidity ^0.8.0;

contract Fibonacci {
    uint[10] public fib;

    function generate() public {
        fib[0] = 0;
        fib[1] = 1;
        for(uint i=2;i<10;i++) {
        fib[i] = fib[i-1] + fib[i-2];
        }
    }
}

Generates first 10 Fibonacci numbers stored in an array.

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Solidity Max of Two Numbers

pragma solidity ^0.8.0;

contract MaxProgram {
    uint public a = 7;
    uint public b = 10;
    uint public max;

    function findMax() public {
        max = a > b ? a : b;
    }
}

Finds the maximum of two numbers.

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Solidity Array Sum

pragma solidity ^0.8.0;

contract ArraySum {
    uint[5] public nums = [1,2,3,4,5];
    uint public sum;

    function calculateSum() public {
        sum = 0;
        for(uint i=0;i<nums.length;i++) {
        sum += nums[i];
        }
    }
}

Sums elements of an array and stores in a state variable.

Let’s Try →

Solidity Even Numbers Filter

pragma solidity ^0.8.0;

contract EvenNumbers {
    uint[10] public nums = [1,2,3,4,5,6,7,8,9,10];
    uint[] public evens;

    function filter() public {
        delete evens;
        for(uint i=0;i<nums.length;i++) {
        if(nums[i] % 2 == 0) {
        evens.push(nums[i]);
        }
        }
    }
}

Returns even numbers from an array.

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Solidity String Concatenation

pragma solidity ^0.8.0;

contract ConcatStrings {
    string public str1 = 'HELLO';
    string public str2 = 'WORLD';
    string public result;

    function concat() public {
        result = string(abi.encodePacked(str1, str2));
    }
}

Concatenates two strings and stores in a state variable.

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Solidity Counter With Loop Simulation

pragma solidity ^0.8.0;

contract LoopCounter {
    uint public count;

    function run() public {
        count = 1;
        while(count <= 5) {
        count++;
        }
    }
}

Counts from 1 to 5 using a loop and stores the final count.

Let’s Try →

Solidity Conditional Increment

pragma solidity ^0.8.0;

contract ConditionalIncrement {
    uint public count = 3;

    function run() public {
        if(count < 5) {
        count++;
        }
    }
}

Increment counter only if it is less than 5.

Let’s Try →

Frequently Asked Questions about Solidity

What is Solidity?

What are the primary use cases for Solidity?

Smart contract development. DeFi protocols (DEXs, lending, staking). NFT standards (ERC-721, ERC-1155). Token creation (ERC-20). DAO governance mechanisms. Permissioned enterprise blockchain apps

What are the strengths of Solidity?

Native support for Ethereum standards. Large community & ecosystem. Powerful for financial logic. Extensive tooling (Hardhat, Foundry, Truffle). Rich developer resources

What are the limitations of Solidity?

Security vulnerabilities are common. Gas-cost constraints. Upgradability complexity. Difficult debugging across chains. Blockchain immutability adds risk

How can I practice Solidity typing speed?

CodeSpeedTest offers 10+ real Solidity code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.