Thread: calculate average with an unknown number of inputs

I'm supposed to write a program that outputs the average from an unknown amount of inputs. For that I will use a sentinel value (-1) to end the while loop. Also, the program will use a for loop that will call the function four times. Each time I will enter a new set of number and each time the average will be printed.

Code:

#include <stdio.h>


void calculateAverage (void);


int main(void) {


int i;
float average;


for (i = 1; i <= 4; ++i) {
     calculateAverage();
}


return 0;
}


void calculateAverage (void) {


int sumofGrades = 0;
int numberofGrades = 0;
float average = 0.0;
int grade = 0;


        while(grade != -1 && grade >= 0 && grade <= 100) {


                if(grade != -1) {


              numberofGrades++;
              sumofGrades += grade;
                }
              printf("Enter grades and type -1 to stop: \n");
              scanf("%d", &grade);






        }




     average = (float)sumofGrades / numberofGrades;
     printf("The average is %.2f\n", average);


}

The output that I get is this:

Enter grades and type -1 to stop:
3 5 6 8 -1
Enter grades and type -1 to stop:
Enter grades and type -1 to stop:
Enter grades and type -1 to stop:
Enter grades and type -1 to stop:
The average is 4.40
Enter grades and type -1 to stop: