ERC20.sol

//SPDX-License-Identifier: UNLICENSED

pragma solidity >=0.6.0 <0.9.0; // ---------------------------------------------------------------------------- // EIP-20: ERC-20 Token Standard // https://eips.ethereum.org/EIPS/eip-20 // -----------------------------------------
interface ERC20Interface { 
function totalSupply() external view returns (uint); 
function balanceOf(address tokenOwner) external view returns (uint balance); 
function transfer(address to, uint tokens) external returns (bool success);

function allowance(address tokenOwner, address spender) external view returns (uint remaining);
function approve(address spender, uint tokens) external returns (bool success);
function transferFrom(address from, address to, uint tokens) external returns (bool success);

event Transfer(address indexed from, address indexed to, uint tokens);
event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

contract Block is ERC20Interface{ 
    string public name="Block";    
    string public symbol ="TANQ";
    string public decimal="0";

uint public override totalSupply;
address public founder;
mapping(address=>uint) public balances;
mapping(address=>mapping(address=>uint)) allowed;

constructor(){
    totalSupply=99;
    founder=msg.sender;
    balances[founder]=totalSupply;
}

function balanceOf(address tokenOwner) public view override returns(uint balance){
    return balances[tokenOwner];
}

function transfer(address to,uint tokens) public override returns(bool success){   //Transfering Tokens
    require(balances[msg.sender]>=tokens);
    balances[to]+=tokens; 
    balances[msg.sender]-=tokens;
    emit Transfer(msg.sender,to,tokens);
    return true;
}

function approve(address spender,uint tokens) public override returns(bool success){ // Owner->Spender->Reciever(Giving Allowance  To Spend From Owner Amount But Spender is different)
    require(balances[msg.sender]>=tokens);
    require(tokens>0);
    allowed[msg.sender][spender]=tokens;
    emit Approval(msg.sender,spender,tokens);
    return true;
}

function allowance(address tokenOwner,address spender) public view override returns(uint noOfTokens){  // allowance Given
    return allowed[tokenOwner][spender];
}

function transferFrom(address from,address to,uint tokens) public override returns(bool success){
    require(allowed[from][to]>=tokens);
    require(balances[from]>=tokens);
    balances[from]-=tokens;
    balances[to]+=tokens;
    return true;
}
}