按值传递（Call by value）是指将参数的值复制给函数中的形参，函数中对形参的修改不会影响到原始参数的值。

示例代码：

#include 

void increment(int num) {
    num++;
    std::cout << "Inside increment function: " << num << std::endl;
}

int main() {
    int num = 5;
    std::cout << "Before calling increment function: " << num << std::endl;
    increment(num);
    std::cout << "After calling increment function: " << num << std::endl;
    return 0;
}

输出：

Before calling increment function: 5
Inside increment function: 6
After calling increment function: 5

通过指针引用（Call by reference to a pointer）是指将参数的地址传递给函数中的形参，函数中对形参的修改会影响到原始参数的值。

示例代码：

#include 

void increment(int* pNum) {
    (*pNum)++;
    std::cout << "Inside increment function: " << *pNum << std::endl;
}

int main() {
    int num = 5;
    std::cout << "Before calling increment function: " << num << std::endl;
    increment(&num);
    std::cout << "After calling increment function: " << num << std::endl;
    return 0;
}

输出：

Before calling increment function: 5
Inside increment function: 6
After calling increment function: 6