#include<stdio.h>
#include <stdlib.h>
int main()
{
    FILE *input,*charge;
    float a,b;
    int i;
    struct
    {
        int num;
        int count1;
        int count2;
        float sum;         
    }id[6];
      
    input=fopen("input.dat","r+");
    if(input == NULL)
    {
             printf("Open file error!\n");
             return 1;
    }
    fscanf(input,"%f%f",&a,&b);
    printf("NO.\tcount1\tcount2\n");
    for(i=0;i<6;i++)
    {
             fscanf(input,"%d%d%d",&id[i].num,&id[i].count1,&id[i].count2);
             printf("%d \t %d \t %d\n",id[i].num,id[i].count1,id[i].count2);              
    }
    fclose(input);
      
    charge=fopen("charge.dat","a+");
    if(charge == NULL)
    {
             printf("Open file error!\n");
             return 1;
    }
    fputs("NO.",charge);
    fputs("\tmoney1\tmoney2\tsum\n",charge);
    for(i=0;i<6;i++)
    {
             fprintf(charge,"%d \t %.1f \t %.1f \t%.1f \n",id[i].num,id[i].count1*a,id[i].count2*b,id[i].count1*a+id[i].count2*b);              
    }
      
}  

a b 是神马都是浮云。不见赋值呢

要看看 input.dat 文件的数据结构才好说。