int x = 10, y = 20;

// 1. Regular reference (must bind to lvalue)
int& ref1 = x;     // ref1 IS x ✓ Can modify x via ref1
ref1 = 30;         // x becomes 30

// 2. Const reference (read-only view)
const int& ref2 = x;  // ref2 sees x, can't modify
// ref2 = 40;        // ERROR!

// 3. Const ref extends lifetimes (temporary binding)
const int& ref3 = 5;  // Binds to rvalue, lives until ref3 destroyed

// 4. Function params (industry standard)
void print(const int& val) { cout << val; }  // Safe, efficient