Create DemoToken.sol

DemoToken.sol

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+//SPDX-License-Identifier: MIT
+    /** Visibility of a function
+    public, private, external, internal
+    * msg.sender
+    * alt + arrow up/down
+    * shortcut to comment a line: ctrl + /
+    * TWO TYPES OF FUNCTIONS: 1. WRITABLE FUNCTIONS 2. READABLE FUNCTIONS
+    */
+
+pragma solidity ^0.8.0;
+
+contract OphirArbitrum{
+    // 1. Create our token's total Supply
+    uint256 public maxSupply = 210000000;
+    uint256 public totalAvailableSupply = 21000000;
+
+    mapping(address => uint256) balance;
+
+    // 2. The minting function
+    function mintToken(address receiver, uint256 amount) public{
+        totalAvailableSupply = totalAvailableSupply - amount;
+        balance[receiver] = balance[receiver] + amount;
+    }
+
+    //balance[location]
+
+
+    // 3. A function to check to checkBalance 
+    function checkBalance(address account) public view returns(uint256) {
+        return balance[account];
+    }
+
+
+    // 4. Create the transfer function
+    // Send some amount of tokens from one account to another account
+    function transfer(address sender, address receiver, uint256 amount) public {
+        balance[sender] = balance[sender] - amount;
+        balance[receiver] = balance[receiver] + amount;
+    }
+
+}