int load()
{
    FILE*fp;
    struct systm sb[N];
    fp=fopen("D:\\z\\systm\\subjct.dat","rb");
    int i=0,g=0,j=0;
    if((fp=fopen("D:\\z\\systm\\subjct.dat","rb"))=NULL)
    {
        printf("\nCan not open load file\n");
        exit(1);
     }
    while(!feof(fp))
         {
             if(1!=fread(&sb[i],sizeof(struct systm),1,fp)) break;
             i++;
             ++j;
             ++g;
         }
    fclose(fp);
    printf("%d",g);
    return(g);          //返回课程信息记录个数
}