程序代码：

#include <stdio.h>
#define N 100
int main()
{
    int i=0,num=0;
    float salary[N],sum=0,ave=0;
    printf("Input everyone's salary:\n");
    for(;i<N;i++)
    {
        scanf("%f",&salary[i]);
        if(salary[i]!=-1)    
        {
            sum+=salary[i];    
            num++;
        }        
        else break;
    }
    printf("the average salary=%.2f\n",sum/num);
    return 0;
}