Learn SOLIDITY with Real Code Examples

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.