怎么实现清除记事本里的数据再重新往记事本里写数据？求解答，谢谢

FILE *fp;
       if((fp=fopen("data.txt","r+"))==NULL)
         {
           printf("can't open the file!");
           exit(0);
         }
       fscanf(fp,"%d",&i);
       printf("The data is:");
       printf("%d\n",i);
       i++;
       fprintf(fp,"%d",i);
怎么实现每次从记事本里读出来的数据都加1？还请高手多多指点，谢谢