#include<stdio.h>
#include<math.h>

#define CORRECT      0
#define FILE_OPEN_ERROR    1
#define FILE_ERROR    2

int main()
{
    int t,a,b,n,k,j,sum=0;
        FILE *    fp = fopen("data.in","r");
        if (fp==NULL){
        printf("error 1\n");
        return 1;
    }
         t    =    fscanf(fp,"%d %d",&a,&b);
         if( t != 2){
             fprintf(stderr,"file empty!\n");
             fclose(fp);
             return FILE_ERROR;
         }

           if (a<0 || b<0 || a>b ){
                     fprintf(stderr,"error 2\n");
                     fclose(fp);
        return 2;
        }
    for (i = a;i < b; i++){
        k    =sqrt(i);
        for (j = 2; j<=k ;j++);
            
            if (i%j == 0)
                break;
    if (j>=k){
        printf("%-4d",n);:
        sum = sum + n;
}
}
printf("%d %d \n",a,b);


printf("%d\n",sum);
return 0;
}
 从data.in里读出数据，再计算。  data.in 是与这个文件同目录下的文件，里面有两个数

好吧，代码有点乱，我错啦，
但是最终素数输出来了，但是素数之和怎么是错的呢？
data.in里是10 20 输出的素数之和却是165