/**
 * file: main.c
 * author: 简单教程(www.twle.cn)
 *
 * Copyright © 2015-2065 www.twle.cn. All rights reserved.
 */

#include <stdio.h>


struct student
{
    int x;
    char c;
} a;


void f(struct student b)
{
    b.x = 20;
    b.c = 'y';
}


int main()
{
    a.x = 3;
    a.c = 'a';
    f(a);
    printf("%d,%c\n",a.x,a.c);
}

$ gcc main.c && a.out
3,a