#include<stdio.h>

int main(void)
{
    int num;
    double input;
    int b = 0;
    double sum = 0;
    scanf("%d", &num);

    while (b++<num)
    {
        scanf("%lf", &input);
        sum += input;
    }
    printf("%f\n", sum);
    return 0;
}


我编辑了一段，就是输入你要输入几个实数，之后输入完的所有实数相加的简单编辑
我想让他在input.txt里输入后
把结果输出在output.txt里

#include<stdio.h>
#include<stdlib.h>

int main(void)
{
    FILE *fpr,*fpw;
    if((fpr=fopen("test1.txt","r")==NULL){
      fprintf(stderr,"can't open test1.txt");
      exit(1);
    }
     if((fpw=fopen("test2.txt","w")==NULL){
      fprintf(stderr,"can't open test2.txt");
      exit(1);
    }
   
    int num;
    double input;
    int b = 0;
    double sum = 0;
    scanf("%d", &num);

    while (b++<num)
    {
        fread(&input,sizeof(double),1,fpr);
        sum += input;
        fwrite(&input,sizeof(double),1,fpw);
    }
   /* printf("%f\n", sum);*/
    return 0;
}

#include<stdio.h>
#include<stdlib.h>

int main()
{
    FILE *fp;
    int num;
    double input;
    int b = 0;
    double sum = 0;

    fp = fopen("input.txt", "r");
    fscanf(fp, "%d", &num);

    while (b++<num)
    {
        fscanf(fp, "%lf", &input);
        sum += input;
    }
    fclose(fp);

    fp = fopen("output.txt", "w");
    fprintf(fp, "%f", sum);

    fclose(fp);
}
我自己试着编辑了下，不过不能运行，请问我这编辑哪里该修正呢？

我试着运行了一下没问题，不知道你是不是没有input.txt