string msg;
msg = "Hello";

var msg = "Hello";

const double Phi = 1.618;

string str = "Hello";

string str = @"Multiline
string";

string name = "World";
string greeting = $"Hello, {name}!";

/// | `short`| 16-bit | -2¹⁵ ~ 2¹⁵-1 | -32,768 ~ 32,767 | 正負 3 萬，4 位數 |
/// | `int`  | 32-bit | -2³¹ ~ 2³¹-1 | -2.1B ~ 2.1B     | 正負 21 億，10 位數|
///| `long`  | 64-bit | -2⁶³ ~ 2⁶³-1 | -9.2E ~ 9.2E     | 正負 922 京，19 位數|
byte b = 255;
short s = 32000;
int num = 3;
long l = 100000L;

///| `float`   | 32-bit  | ±3.4×10³⁸  | ~7 位數  |
///| `double`  | 64-bit  | ±1.7×10³⁰⁸ | ~15 位數 |
///| `decimal` | 128-bit | ±7.9×10²⁸  | ~28 位數 |
float f = 3.14f;
double d = 3.14;
decimal m = 3.14m;

// Fixed size array
int[] numbers = new int[5];

// Array with initializer
int[] numbers = { 1, 2, 3, 4, 5 };

// Multi-dimensional array
int[,] matrix = new int[3, 3];