• Owner
• Account create function
• Deposit function
• Withdraw function
• Transfer function
• Get balance
• All balance

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.16;
contract Bank{
address owner;mapping(address=>uint) public account;
mapping(address=>bool) public userExist; //check if user existconstructor(){
owner=msg.sender;
}
}

function createAccount()public returns(bool){
require(userExist[msg.sender]==false,"user existed");
userExist[msg.sender]=true;
return true;
}

function deposit(uint amountDeposit) public payable returns(bool){
amountDeposit>0;
account[msg.sender]=account[msg.sender]+amountDeposit;
return true;
}

function withdraw(uint amountWithdraw)public payable {
account[msg.sender]>=amountWithdraw;
account[msg.sender]=account[msg.sender]-amountWithdraw;
}

function transfer(address add,uint amountTransfer) public{
require(userExist[add]==true,"account not existed");
account[msg.sender]>=amountTransfer;
account[msg.sender]=account[msg.sender]-amountTransfer;account[add]=account[add]+amountTransfer;
}

function checkBalnce() public view returns(uint){
return account[msg.sender];
}

function getAllBalance() public view returns(uint){
return address(this).balance;
}

• To check that the owner who run the function
• This modifier use in getAllBalance function

modifier onlyOwner(){
require(msg.sender==owner,"you are not the owner");
_;
}

• This modifier use in deposit -withdraw-transfer-checkbalance function

modifier isUserExisted(){
require(userExist[msg.sender]==true,"account not existed");
_;
}

• use msg.value in deposit function
• delete parameter in deposit function

function deposit() public payable returns(bool){
msg.value>0;
account[msg.sender]=account[msg.sender]+msg.value;
return true;
}

All code

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.16;
contract Bank{address owner;
mapping(address=>uint) public account;
mapping(address=>bool) public userExist;
constructor(){
owner=msg.sender;
}modifier onlyOwner(){
require(msg.sender==owner,"you are not the owner");
_;
}modifier isUserExisted(){
require(userExist[msg.sender]==true,"account not existed");
_;
}function createAccount()public returns(bool){
require(userExist[msg.sender]==false,"user existed");
userExist[msg.sender]=true;
return true;
}function deposit() public payable isUserExisted returns(bool){
msg.value>0;
account[msg.sender]+=msg.value;
return true;
}function withdraw(uint amountWithdraw)public payable isUserExisted {
account[msg.sender]>=amountWithdraw;
account[msg.sender]-=amountWithdraw;
}function transfer(address add,uint amountTransfer) public isUserExisted{
require(userExist[add]==true,"account not existed");
account[msg.sender]>=amountTransfer;
account[msg.sender]-=amountTransfer;
account[add]+=amountTransfer;
}function checkBalnce() public view isUserExisted  returns(uint){
return account[msg.sender];
}function getAllBalance() public view onlyOwner returns(uint){
return address(this).balance;
}
}

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