C语言三种参数传递方式

值传递、指针传递、引用传递

只有在函数调用时，才会为形参分配内存空间，调用结束便会释放。

值传递和指针传递，传递的都是实参的一份拷贝。

C语言在线编译器：http://www.dooccn.com/c/

值传递：

#include <stdio.h>

void exchange(int x, int y)
{
    int tmp;
    tmp = x;
    x = y;
    y = tmp;
    printf("x=%d,&x=%d
y=%d,&y=%d
",x,&x,y,&y);
}

int main(void) 
{ 
    int a=3, b=4;
    printf("a=%d,&a=%d
b=%d,&b=%d
",a,&a,b,&b);
    exchange(a,b);
    printf("a=%d,&a=%d
b=%d,&b=%d
",a,&a,b,&b);
    return 0;
}

结果：

a=3,&a=17295016
b=4,&b=17295020
x=4,&x=17294972
y=3,&y=17294968
a=3,&a=17295016
b=4,&b=17295020

地址传递：

#include <stdio.h>

void exchange(int *x, int *y)
{
    int *tmp=NULL;
    tmp = x;
    x = y;
    y = tmp;
    printf("*x=%d, x=%d
", *x, x);
    printf("*y=%d, y=%d
", *y, y);
}

int main(void) 
{ 
    int a=3, b=4;
    printf("a=%d, &a=%d
", a, &a);
    printf("b=%d, &b=%d
", b, &b);
    exchange(&a,&b);
    printf("a=%d, &a=%d
", a, &a);
    printf("b=%d, &b=%d
", b, &b);
    return 0;
}

结果：

a=3, &a=-892176920
b=4, &b=-892176916
*x=4, x=-892176916
*y=3, y=-892176920
a=3, &a=-892176920
b=4, &b=-892176916

引用传递

#include <stdio.h>

void exchange(int &x, int &y)
{
    int tmp;
    tmp = x;
    x = y;
    y = tmp;
    printf("x=%d, &x=0x%d
", x, &x);
    printf("y=%d, &y=0x%d
", y, &y);
}

int main(void) 
{ 
    int a=3, b=4;
    printf("a=%d, &a=0x%d
", a, &a);
    printf("b=%d, &b=0x%d
", b, &b);
    exchange(a,b);
    printf("a=%d, &a=0x%d
", a, &a);
    printf("b=%d, &b=0x%d
", b, &b);
    return 0;
}

结果：

a=3, &a=0x1079344872
b=4, &b=0x1079344876
x=4, &x=0x1079344872
y=3, &y=0x1079344876
a=4, &a=0x1079344872
b=3, &b=0x1079344876