Learn Solidity: Input and Output Parameters of Functions

In this post, we will understand the how Input & output Parameters can be defined in Solidity Language.

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pragma solidity 0.4.8; 

* @title An Example
* @author Toshendra Sharma
* @notice Example for the Solidity Course

// As in Javascript, functions may take parameters as input; 
// unlike in Javascript and C, they may also return arbitrary number of parameters as output.

// The input parameters are declared the same way as variables are. 
// As an exception, unused parameters can omit the variable name. 

contract InputAndOutputParameters {

    uint public constructorInput1;
    address public constructorInput2;
    uint public sum;
    uint public product;
    uint public multiplyByThreeValue;

    // For example, suppose we want our contract to accept  
    //two parameters, we would write something like:
    function InputAndOutputParameters(uint _inputParam1, address _inputParam2) {
       // Initialize state variables here
       constructorInput1 = _inputParam1;
       constructorInput2 = _inputParam2;

    // The output parameters can be declared with the same syntax after the returns keyword. 
    // For example, suppose we wished to return  one value: then we would write this:

    function multiplyByThree(uint _inputParam1) returns (uint m){
        multiplyByThreeValue = _inputParam1 * 3;
        m = multiplyByThreeValue;

    // Let's say we want to return two values the we would write something like this

    function sumAndProduct1(uint _inputParam1, uint _inputParam2) returns (uint s, uint p){
        sum = _inputParam1 + _inputParam2;
        product = _inputParam1 * _inputParam2;
        s = sum;
        p = product;

    // please note that variables name can be ommitted in returns as well as in function call.
    function sumAndProduct2(uint _inputParam1, uint _inputParam2) returns (uint, uint){
        sum = _inputParam1 + _inputParam2;
        product = _inputParam1 * _inputParam2;
        return (sum, product);

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