Data types in Solidity
Here we introduce you to some primitive data types available in Solidity.
boolean
The possible values are constantstrue
andfalse
uintint
/uint
: Signed and unsigned integers of various sizes. Keywordsuint8
touint256
in steps of8
(unsigned of 8 up to 256 bits) andint8
toint256
.uint
andint
are aliases foruint256
andint256
, respectively.address
The address type comes in two flavors, which are largely identical:address
: Holds a 20-byte value (the size of an Ethereum address).address payable
: Same asaddress
, but with the additional memberstransfer
andsend
.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;
contract Primitives {
bool public boo = true;
/*
uint stands for unsigned integer, meaning non negative integers
different sizes are available
uint8 ranges from 0 to 2 ** 8 - 1
uint16 ranges from 0 to 2 ** 16 - 1
...
uint256 ranges from 0 to 2 ** 256 - 1
*/
uint8 public u8 = 1;
uint public u256 = 456;
uint public u = 123; // uint is an alias for uint256
/*
Negative numbers are allowed for int types.
Like uint, different ranges are available from int8 to int256
int256 ranges from -2 ** 255 to 2 ** 255 - 1
int128 ranges from -2 ** 127 to 2 ** 127 - 1
*/
int8 public i8 = -1;
int public i256 = 456;
int public i = -123; // int is same as int256
// minimum and maximum of int
int public minInt = type(int).min;
int public maxInt = type(int).max;
address public addr = 0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c;
/*
In Solidity, the data type byte represent a sequence of bytes.
Solidity presents two type of bytes types :
- fixed-sized byte arrays
- dynamically-sized byte arrays.
The term bytes in Solidity represents a dynamic array of bytes.
It’s a shorthand for byte[] .
*/
bytes1 a = 0xb5; // [10110101]
bytes1 b = 0x56; // [01010110]
// Default values
// Unassigned variables have a default value
bool public defaultBoo; // false
uint public defaultUint; // 0
int public defaultInt; // 0
address public defaultAddr; // 0x0000000000000000000000000000000000000000
}