Functions and structures

Question

#include <stdio.h>

struct n

{

int x;

char c;

};

void func(struct n b){

b.x=20,b.c='y';

}

void main(){

struct n a={10,'x'};

func(a);

printf("%d,%c",a.x,a.c);

}

Why is the final result 10, x please answer it