#include<stdio.h>
#include<stdlib.h>
void main()
{
    int a[2],c,i;
    FILE *sp,*sb;
    char filename[10],filename2[10];
    printf("please input the filename:(limit in ten data)\n");
    scanf("%s",filename);
    if((sp=fopen(filename,"r"))==NULL)
    {
        printf("open fail!\n");
        exit(0);
    }
    for(i=0;i<2;i++)
   
fread(sp,sizeof(int),1,a[i]);
   
c=a[1]+a[0];
printf("%d",c);
if((sb=fopen(filename,"w"))==NULL)
{
    printf("open fail!\n");
    exit(0);
}
        
printf("input the write filename:\n");
scanf("%s",filename2);
fwrite(c,sizeof(int),1,sb);
printf("over!\n");
fclose(sp);
fclose(sb);
}

谢谢你帮我指出这些错误，但在我改完后还是在运行时出现打开错误，还望你能帮我再指导一下，非常感谢！
#include<stdio.h>
#include<stdlib.h>
void main()
{
    int a[2],c,i;
    FILE *sp,*sb;
    char filename[10],filename2[10];
    printf("please input the filename:(limit in ten data)\n");
    scanf("%s",filename);
    if((sp=fopen(filename,"rb"))==NULL)
    {
        printf("open fail!\n");
        exit(0);
    }
    for(i=0;i<2;i++)
   
fread(&a[i],sizeof(int),1,sp);
   
c=a[1]+a[0];
printf("%d",c);
if((sb=fopen(filename,"wb"))==NULL)
{
    printf("open fail!\n");
    exit(0);
}
        
printf("input the write filename:\n");
scanf("%s",filename2);
fwrite(&c,sizeof(int),1,sb);
printf("over!\n");
fclose(sp);
fclose(sb);
}

不啊，我上面是一个是read文件，一个是write文件啊，难道说两个文件要一起打开吗

好 ，谢谢