#include "stdio.h"
#include "conio.h"
#include "math.h"
main()
{
  int grade;
  long profit;
  int salary=500;
  printf("input profit");
  scanf("%ld",&profit);
  grade=(profit-1)/1000;
  switch(grade)
   {
    case 0:salary+=profit*0;break;
    case 1:salary+=profit*0.10;break;
    case 2:
    case 3:
    case 4:salary+=profit*0.15;break;
    case 5:
    case 6:
    case 7:
    case 8:
    case 9:salary+=profit*0.20;break;
    default:salary+=profit*0.25;
   }
  printf("salary is %.2d",salary);
    getch();
}
输入3000时得949  



#include "stdio.h"
#include "conio.h"
#include "math.h"
main()
{
  int grade;
  long profit;
  float salary=500;
  printf("input profit");
  scanf("%ld",&profit);
  grade=(profit-1)/1000;
  switch(grade)
   {
    case 0:salary+=profit*0;break;
    case 1:salary+=profit*0.10;break;
    case 2:
    case 3:
    case 4:salary+=profit*0.15;break;
    case 5:
    case 6:
    case 7:
    case 8:
    case 9:salary+=profit*0.20;break;
    default:salary+=profit*0.25;
   }
  printf("salary is %.2f",salary);
    getch();
}
输3000时得950.00
为什么？？？