程序代码：

#include<stdio.h>

struct x{
    int a;
    int b;
};

struct y{
    int c;
    int d;
};

int main(){
    FILE *fp1,*fp2;
    struct x test1 = {1,2};
    struct y test2 = {3,4};
    fp1 = fopen("test.dat","w+b");
    fp2 = fopen("test.dat","r+b");
    fwrite(&test1.a,sizeof(test1.a),1,fp1);
    fwrite(&test1.b,sizeof(test1.b),1,fp1);
    fread(&test2.c,sizeof(test1.a),1,fp2);
    fread(&test2.d,sizeof(test1.b),1,fp2);
    fclose(fp1);
    fclose(fp2);
    printf("%d,%d\n",test2.c,test2.d);
    return 0;
}