ERC20.sol

pragma solidity >=0.4.0 <0.7.0;

// ----------------------------------------------------------------------------
// 'TestCoin' token contract
//
// Deployed to : 
// Symbol      : TESTCO
// Name        : 0 Test Coin
// Total supply: 100000000
// Decimals    : 18
//
//
// ----------------------------------------------------------------------------




// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract TESTCoin  {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;

    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);

    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------
    constructor() public {
        symbol = "TESTCO";
        name = "Test Coin";
        decimals = 18;
        _totalSupply = 100000000000000000000000000;
        balances[msg.sender] = _totalSupply;
        
    }


    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------
    function totalSupply() public view returns (uint) {
        return _totalSupply  - balances[address(0)];
    }


    // ------------------------------------------------------------------------
    // Get the token balance for account tokenOwner
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public view returns (uint balance) {
        return balances[tokenOwner];
    }


    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to to account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = (balances[msg.sender]- tokens);
        balances[to] = (balances[to] +  tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Transfer tokens from the from account to the to account
    // 
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the from account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = (balances[from] - tokens);
        allowed[from][msg.sender] = (allowed[from][msg.sender] - tokens);
        balances[to] = (balances[to] + tokens);
        emit Transfer(from, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }


    // ------------------------------------------------------------------------
    // Token owner can approve for spender to transferFrom(...) tokens
    // from the token owner's account. The spender contract function
    // receiveApproval(...) is then executed
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint tokens, bytes memory data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }

   
}