Update Version match ^0.5.0

ERC20Interface.sol

@@ -1,18 +1,20 @@
+pragma solidity >=0.4.22 <0.7.0;
+
 contract ERC20Interface {
 
     string public constant name = "Token Name";
     string public constant symbol = "SYM";
     uint8 public constant decimals = 18;  // 18 is the most common number of decimal places
     // 0.0000000000000000001  个代币
 
-    function totalSupply() public constant returns (uint);
+    function totalSupply() external view returns (uint);
 
-    function balanceOf(address tokenOwner) public constant returns (uint balance);
+    function balanceOf(address tokenOwner) external view returns (uint balance);
 
-    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
-    function approve(address spender, uint tokens) public 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 transfer(address to, uint tokens) public returns (bool success);
+    function transfer(address to, uint tokens) external returns (bool success);
     function transferFrom(address from, address to, uint tokens) public returns (bool success);
 
 

MyAdvancedToken.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.20;
+pragma solidity >=0.4.22 <0.7.0;
 
 
 import "./owned.sol";
@@ -21,13 +21,13 @@ contract MyAdvancedToken is owned, TokenERC20 {
     /* Initializes contract with initial supply tokens to the creator of the contract */
     constructor (
         uint256 initialSupply,
-        string tokenName,
-        string tokenSymbol
+        string memory tokenName,
+        string memory tokenSymbol
     ) TokenERC20(initialSupply, tokenName, tokenSymbol) payable public {}
 
     /* Internal transfer, only can be called by this contract */
     function _transfer(address _from, address _to, uint _value) internal {
-        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
+        require (_to != address(0x0));                               // Prevent transfer to 0x0 address. Use burn() instead
         require (balanceOf[_from] >= _value);               // Check if the sender has enough
         require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
         require(!frozenAccount[_from]);                     // Check if sender is frozen
@@ -43,8 +43,8 @@ contract MyAdvancedToken is owned, TokenERC20 {
     function mintToken(address target, uint256 mintedAmount) onlyOwner public {
         balanceOf[target] += mintedAmount;
         totalSupply += mintedAmount;
-        emit Transfer(0, this, mintedAmount);
-        emit Transfer(this, target, mintedAmount);
+        emit Transfer(address(0), address(this), mintedAmount);
+        emit Transfer(address(this), target, mintedAmount);
     }
 
     /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
@@ -66,14 +66,14 @@ contract MyAdvancedToken is owned, TokenERC20 {
     /// @notice Buy tokens from contract by sending ether
     function buy() payable public {
         uint amount = msg.value / buyPrice;               // calculates the amount
-        _transfer(this, msg.sender, amount);              // makes the transfers
+        _transfer(address(this), msg.sender, amount);              // makes the transfers
     }
 
     /// @notice Sell `amount` tokens to contract
     /// @param amount amount of tokens to be sold
     function sell(uint256 amount) public {
-        require(this.balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
-        _transfer(msg.sender, this, amount);              // makes the transfers
+        require(address(this).balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
+        _transfer(msg.sender, address(this), amount);              // makes the transfers
         msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
     }
 }

TokenERC20.sol

@@ -1,6 +1,6 @@
-pragma solidity ^0.4.20;
+pragma solidity >=0.4.22 <0.7.0;
 
-interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }
+interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes calldata _extraData) external; }
 
 contract TokenERC20 {
     string public name;
@@ -22,7 +22,7 @@ contract TokenERC20 {
     /**
      * 初始化构造
      */
-    constructor(uint256 initialSupply, string tokenName, string tokenSymbol) public {
+    constructor(uint256 initialSupply, string memory tokenName, string memory tokenSymbol) public {
         totalSupply = initialSupply * 10 ** uint256(decimals);  // 供应的份额，份额跟最小的代币单位有关，份额 = 币数 * 10 ** decimals。
         balanceOf[msg.sender] = totalSupply;                // 创建者拥有所有的代币
         name = tokenName;                                   // 代币名称
@@ -34,7 +34,7 @@ contract TokenERC20 {
      */
     function _transfer(address _from, address _to, uint _value) internal {
         // 确保目标地址不为0x0，因为0x0地址代表销毁
-        require(_to != 0x0);
+        require(_to != address(0x0));
         // 检查发送者余额
         require(balanceOf[_from] >= _value);
         // 确保转移为正数个
@@ -97,12 +97,12 @@ contract TokenERC20 {
      * @param _value 最大可花费代币数
      * @param _extraData 发送给合约的附加数据
      */
-    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
+    function approveAndCall(address _spender, uint256 _value, bytes memory _extraData)
         public
         returns (bool success) {
         tokenRecipient spender = tokenRecipient(_spender);
         if (approve(_spender, _value)) {
-            spender.receiveApproval(msg.sender, _value, this, _extraData);
+            spender.receiveApproval(msg.sender, _value, address(this), _extraData);
             return true;
         }
     }

owned.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.16;
+pragma solidity >=0.4.22 <0.7.0;
 
 contract owned {
     address public owner;