C函数的实参与形参的输出区别

#include <stdio.h>

int swap(int a,int b)
{
    int temp;
    temp=a;
    a=b;
    b=temp;
    printf("in the swap,a=%d,b=%d\n",a,b);
}

int main()
{
    int a=2;
    int b=5;
    printf("a=%d,b=%d\n",a,b);
    swap(a,b);
    printf("after swap,a=