#include "stdio.h"
int main (void)
{
  float sales,salary=0;
  
  
  printf ("Enter sales in dollars (-1 to end): ");
  scanf ("%f",sales);
  
  while ( sales != -1){
     salary = (float)sales * 9/100 + i;
     printf ("salary is : %.2f\n",salary);
     printf ("Enter sales in dollars (-1 to end): ");
     scanf ("%f",sales);
  }
  
  return 0;
}
到底怎么改啊，救命

不好意思，发现错误了，脑袋卡边了，没写&

#include <stdio.h>
int main (void)
{
  float sales,salary=0;
  
  
  printf ("Enter sales in dollars (-1 to end): ");
  scanf ("%f",&sales);
  salary = (float)sales * 9/100 + 200;
  printf ("salary is : %.2f\n\n",salary);
  
  while ( sales != -1){
     printf ("Enter sales in dollars (-1 to end): ");
     scanf ("%f",&sales);
    salary = (float)sales * 9/100 + 200;
     printf ("salary is : %.2f\n\n",salary);
  }
  
  return 0;
}
我这么写的，要不无限死循环