Passing by pointer allows a function to receive the address of an object through a pointer parameter. The function can then use the pointer to access or modify the original object.

Unlike a reference parameter, a pointer parameter can also represent a null pointer, allowing the function to determine whether a valid object was supplied.

Source Code #

#include <iostream>

void updateValue(int* value)
{
    *value = 100;
}

int main()
{
    int number = 50;

    updateValue(&number);

    std::cout << "Number: " << number << '\n';

    return 0;
}

Output #

Number: 100

Explanation #

• int* value declares value as a pointer parameter that can store the address of an int object.
• &number obtains the memory address of the variable number.
• updateValue(&number) passes that address to the function.
• value therefore points to the original number object.
• The dereference operator (*) accesses the object stored at the address held by value.
• *value = 100; modifies the original number variable through the pointer.
• After the function returns, number contains 100.
• Unlike a reference, a pointer can be assigned nullptr to represent the absence of an object.
• A pointer should be dereferenced only when it points to a valid object.