Average grade calculator

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>

/*
Average grade calculator by Goran
*/

int main()
{
    int loop = 0, numberOfTests, grade;
    float average;

    printf("Enter number of tests: "); // asking user to enter number of tests.
    scanf(" %d", &numberOfTests); // gets input from user and stores it into integer numberOfTests.

    while(numberOfTests <= 0){ // while numberOfTests is less or equal to 0 do code bellow.
          printf("You need to enter correct number of tests: "); // prints user that he needs to enter correct number of tests.
          scanf(" %d", &numberOfTests); // gets input from user and stores it into integer numberOfTests.
    }

    printf("\n"); // prints blank space.

    do{
        printf("Enter test grade: "); // asking user to enter test grade.
        scanf(" %d", &grade); // gets input from user and stores it into integer grade.
        average += grade; // average float.
        loop++; // increment integer loop by one.
    }while(loop != numberOfTests); // do code above while loop is not equal to numberOfTests.

    average /= numberOfTests; // formula for calculating average grade.

    if(numberOfTests > 1){ // if number of tests user enter is more then 1.
       printf("Average grade from %d tests is %.2f \n \n", numberOfTests, average); // if statement above is true it will print out this line to user.
    }else{
       printf("Average grade from 1 test is %.2f \n \n", average); // else if statement above is not true it will print out this line to user.
    }

    system("pause"); // pausing program after executing.
    return 0;
}