Pointers and References C++

Pointers and references as parameters

• Pointer
• Reference
• Non-pointer and non-reference

Pointer

We pass the address of integer x and the address of integer y to the function.

void swap1(int *a, int *b) 
{ 
    int temp = *a; 
    *a = *b; 
    *b = temp; 
} 
 
int main() 
{ 
    int x = 6; 
    int y = 9; 
    swap1(&x, &y); // x = 9, y = 6 
    return 0; 
} 

Reference

int &a = x represents a is a reference to x (a nickname to x), int &b = y represents b is a reference to y (a nickname to y). So a and b mean x and y themselves. Changing a and b will result in the change of x and y.

void swap2(int &a, int &b) 
{ 
    int temp = a; 
    a = b; 
    b = temp; 
} 
 
int main() 
{ 
    int x = 6; 
    int y = 9; 
    swap2(x, y); // x = 9, y = 6; 
    return 0; 
} 

Non-pointer and non-reference

x and y will not be swapped successfully because we only pass a copy of them into the function here.

void swap3(int a, int b) 
{ 
    int temp = a; 
    a = b; 
    b = temp; 
} 
 
int main() 
{ 
    int x = 6; 
    int y = 9; 
    swap3(x, y); // x = 6, y = 9 
    return 0; 
}