contract Mappings{
mapping(uint=> string) public colors; constructor(){ colors[1]= "Red"; colors[2]="Yellow"; } //mapping store data in key value pair here we have colors which contain
//id with color name
}

mapping(address=>uint) public balance;

pragma solidity ^0.5.0;
contract LedgerBalance
{ mapping(address => uint) public balances; function updateBalance(uint newBalance) public { balances[msg.sender] = newBalance; }
}

 mapping(type => type) mappingName;

 mapping(datatype(KEY) => datatype(VALUE)) <Access Specifier> <MAPPING VARIABLE DECLARATION NAME>;

// Solidity program to 
// demonstrate mapping
pragma solidity ^0.4.18; 
   
// Defining contract 
contract mapping_example {
      
    //Defining structure
    struct student 
    {
        // Declaring different 
        // structure elements
        string name;
        string subject;
        uint8 marks;
    }
      
    // Creating a mapping
    mapping (
    address => student) result;
    address[] public student_result;    
}