Understanding data types in solidity programming language

Solidity the language of smart contracts is somewhat similar to java or other Object Oriented Programming(OOP) Languages. Alot data types in solidity are similar to data types of Java or C++, but it does have some very interesting and different data types for specifically writing smart contracts.

1. int and uint:-

int and uint is signed(stores both positive and negative integer) and unsigned(stores only positive integer) integers ranging from 8bits to 256 bits.
In C++ int can store upto 32bits(10^9) and long long upto 64bits(10^18).
In solidity int or int256 can store a value upto 10^77.

int256 a = -2; // signed integer, int == int256
uint256 b = 4; // unsigned integer, uint == uint256

2. bool:-

boolean in solidity is same as other languages except in Solidity bool cannot be converted to integers, as they can in other programming languages.
in C++ we can do this

if(1)
{
   return "Hello World";
}

But the same code will give us error TypeError: Type int_const 1 is not implicitly convertible to expected type bool.

3. address and address payable:-

address is a special data type in solidity to store 20byte size ethereum address.
Here msg.sender is the person or other contract which called this contract.

address owner;

function ownerSetter() public 
{
    owner = msg.sender;  
}

After invoking the ownerSetter() function the value of ownerbecame 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4.

You can use .balance to get the balance of the address.

function checkBalance() public view returns(uint)
{
    return owner.balance;
}

The only difference between address and address payable is that we can actually transfer ether to the address.
address payable is same as address but with additional features like:

• send();
• transfer();
• call();

4. fixed-sized byte arrays:-

fixed-sized byte arrays range from bytes1,bytes2 upto bytes32. byte array store the data in the form of hexadecimal digits. bytes uses less gas as compare to string.

bytes3 public b3 = "abc";
bytes2 public b2 = "ab";

bytes are immutable which means we cannot change the state of the object after it is created.
This will throw us error in remix IDE

bytes3 public b3 = "abc";
b3[1] = 'a';

Also you can not store integers directly in bytes, for e.g.

bytes1 public b1 = 0x61;   // Works
bytes1 public b2 = 1;      // Doesn't Work     
bytes1 public b3 = "1";    // Works

Here b2 will throw error. 0x61 is hexadecimal value of 'a'

5. enum:-

Enum is a user-defined type in Solidity. Think of enum as state manager, for e.g.
If we want to change the state of computer at a given time we can use enum for that.
Enum makes a program easy to read and maintainable.

enum states{Active, Sleep, Terminated}

states public Computer_State = states.Active; // Assigning default value to Active

 function changeStateToSleep() public
 {
     Computer_State = states.Sleep; // Changing state to sleep       
 }

Thank you for reading all the way through. Please let me know if the article (or the code) can be improved in any way in the comments down below.