c语言小练习中的问题

这是题目

以下为题目给的模板

#include "stdio.h"
#include "math.h"
#include "stdlib.h"
double fun(double x)
{
/begin///这里开始填空
double s=0.0;
double k=0.0,b,c;
b=pow(-1,k-1);
c=b*(1/(2*k-1));

  while(1)
  {
      s=s+c;
     
      if(fabs(c)<x)
          break;

    k++;
  }
  return s;

}

/end/

int main()
{
void NONO( );//函数声明
double x,sum;
printf("Enter x:\n");
scanf("%lf",&x);
sum=fun(x);
printf("sum=%.4f\n",sum);
NONO( );
return 0;
}

void NONO( )
{ FILE *fr,*fw;
int i;
double x;
fr=fopen("E:\exam\999999\PROGIN2.DAT","r");
fw=fopen("E:\exam\999999\PROGOUT2.DAT","w");
for(i=1;i<=5;i++)
{ fscanf(fr,"%lf",&x);
fprintf(fw,"s=%.4f\n",fun(x));}
fclose(fr);
fclose(fw);
}
运行无法结束，求解怎么改

#include "stdio.h"
#include "math.h"
#include "stdlib.h"
double fun(double x)
{
    /*begin*/ //这里开始填空
    double s = 0.0, k = 1, c;
    int b = 1;
    while (1)
    {
        c = b * (1 / (2 * k - 1));
        s = s + c;
        b = -b;
        if (fabs(c) < x)
            break;
        k++;
    }
    return s;
}

/*end*/

int main()
{
    void NONO(); //函数声明
    double x, sum;
    printf("Enter x:\n");
    scanf("%lf", &x);
    sum = fun(x);
    printf("sum=%.4f\n", sum);
    NONO( );
    return 0;
}

void NONO()
{
    FILE *fr, *fw;
    int i;
    double x;
    fr = fopen("E:\\exam\\999999\\PROGIN2.DAT", "r");
    fw = fopen("E:\\exam\\999999\\PROGOUT2.DAT", "w");
    for (i = 1; i <= 5; i++)
    {
        fscanf(fr, "%lf", &x);
        fprintf(fw, "s=%.4f\n", fun(x));
    }
    fclose(fr);
    fclose(fw);
}

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for(i=1;i<=5;i++)
循环输入5次。