C语言形参传递

#include 
#include 

void Exchg1(int x, int y) 
{
    printf("x地址 = %p, y地址 = %p.n", &x, &y);
    int tmp;
    tmp = x;
    x = y;
    y = tmp;
    printf("x = %d, y = %d.n", x, y);
}


int main(void)
{
    int a = 4;
    int b = 6;
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    Exchg1(a, b);
    printf("a = %d, b = %d.n", a, b);
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    return 0;
}

Exchg1为值传递，形参x、y为传入参数的复制值

a的地址000000000061fe1c
b的地址000000000061fe18
x地址 = 000000000061fdf0, y地址 = 000000000061fdf8.
x = 6, y = 4.
a = 4, b = 6.
a的地址000000000061fe1c
b的地址000000000061fe18

#include 
#include 



void Exchg2(int *px, int *py)
{
    printf("px的值%pn", px);
    printf("py的值%pn", py);
    int tmp = *px;
    *px = *py;
    *py = tmp;
    printf("*px = %d, *py = %d.n", *px, *py);
}

int main(void)
{
    int a = 4;
    int b = 6;
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    Exchg2(&a, &b);
    printf("a = %d, b = %d.n", a, b);
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    return 0;
}

打印语句如下

a的地址000000000061fe1c
b的地址000000000061fe18
px的值000000000061fe1c
py的值000000000061fe18
*px = 6, *py = 4.
a = 6, b = 4.
a的地址000000000061fe1c
b的地址000000000061fe18

#include 
#include 



void Exchg3(int &x, int &y)
{
    printf("x地址 = %p, y地址 = %p.n", &x, &y);
    int tmp = x;
    x = y;
    y = tmp;
    printf("x地址 = %p, y地址 = %p.n", &x, &y);
    printf("x = %d, y = %d.n", x, y);
}
int main(void)
{
    int a = 4;
    int b = 6;
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    Exchg3(a, b);
    printf("a = %d, b = %d.n", a, b);
    printf("a的地址%pn", &a);
    printf("b的地址%pn", &b);
    return 0;
}

与值传递中唯一变化的地方在于形参中添加取地址符号&，形参x、y的地址与a、b的地址相同

a的地址000000000061fe1c
b的地址000000000061fe18
x地址 = 000000000061fe1c, y地址 = 000000000061fe18.
x地址 = 000000000061fe1c, y地址 = 000000000061fe18.
x = 6, y = 4.
a = 6, b = 4.
a的地址000000000061fe1c
b的地址000000000061fe18