ERC-20 टोकन स्मार्ट अनुबंध को समझें

1pragma solidity ^0.6.0;
2
3interface IERC20 {
4
5    function totalSupply() external view returns (uint256);
6    function balanceOf(address account) external view returns (uint256);
7    function allowance(address owner, address spender) external view returns (uint256);
8
9    function transfer(address recipient, uint256 amount) external returns (bool);
10    function approve(address spender, uint256 amount) external returns (bool);
11    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
12
13
14    event Transfer(address indexed from, address indexed to, uint256 value);
15    event Approval(address indexed owner, address indexed spender, uint256 value);
16}
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1function totalSupply() external view returns (uint256);
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1function balanceOf(address account) external view returns (uint256);
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1function allowance(address owner, address spender) external view returns (uint256);
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1function transfer(address recipient, uint256 amount) external returns (bool);
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1function approve(address spender, uint256 amount) external returns (bool);
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1function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
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1event Transfer(address indexed from, address indexed to, uint256 value);
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1event Approval(address indexed owner, address indexed spender, uint256 value);
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1pragma solidity ^0.8.0;
2
3interface IERC20 {
4
5    function totalSupply() external view returns (uint256);
6    function balanceOf(address account) external view returns (uint256);
7    function allowance(address owner, address spender) external view returns (uint256);
8
9    function transfer(address recipient, uint256 amount) external returns (bool);
10    function approve(address spender, uint256 amount) external returns (bool);
11    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
12
13
14    event Transfer(address indexed from, address indexed to, uint256 value);
15    event Approval(address indexed owner, address indexed spender, uint256 value);
16}
17
18
19contract ERC20Basic is IERC20 {
20
21    string public constant name = "ERC20Basic";
22    string public constant symbol = "ERC";
23    uint8 public constant decimals = 18;
24
25
26    mapping(address => uint256) balances;
27
28    mapping(address => mapping (address => uint256)) allowed;
29
30    uint256 totalSupply_ = 10 ether;
31
32
33   constructor() {
34	balances[msg.sender] = totalSupply_;
35    }
36
37    function totalSupply() public override view returns (uint256) {
38	return totalSupply_;
39    }
40
41    function balanceOf(address tokenOwner) public override view returns (uint256) {
42        return balances[tokenOwner];
43    }
44
45    function transfer(address receiver, uint256 numTokens) public override returns (bool) {
46        require(numTokens <= balances[msg.sender]);
47        balances[msg.sender] = balances[msg.sender]-numTokens;
48        balances[receiver] = balances[receiver]+numTokens;
49        emit Transfer(msg.sender, receiver, numTokens);
50        return true;
51    }
52
53    function approve(address delegate, uint256 numTokens) public override returns (bool) {
54        allowed[msg.sender][delegate] = numTokens;
55        emit Approval(msg.sender, delegate, numTokens);
56        return true;
57    }
58
59    function allowance(address owner, address delegate) public override view returns (uint) {
60        return allowed[owner][delegate];
61    }
62
63    function transferFrom(address owner, address buyer, uint256 numTokens) public override returns (bool) {
64        require(numTokens <= balances[owner]);
65        require(numTokens <= allowed[owner][msg.sender]);
66
67        balances[owner] = balances[owner]-numTokens;
68        allowed[owner][msg.sender] = allowed[owner][msg.sender]-numTokens;
69        balances[buyer] = balances[buyer]+numTokens;
70        emit Transfer(owner, buyer, numTokens);
71        return true;
72    }
73}
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