Average, Minimum, Maximum Grade Computer

#include <cstdlib>
#include <iostream>
#include "firstQuiz.h"
 
using namespace std;
 
      static int studentNo = 1;
      static int zeroInput = 0;
 
      firstQuiz::firstQuiz(int i)
      {
           errorC = i;     
      }
 
      void firstQuiz::errorHandling()
      {
           //static int errorC; //we can use this instead of interface solution
 
           //if there is an error, show the error message
           if (errorC == 1)
              cout << "error: try again: ";
 
           //no problem
           else
               cout << "enter the negative number tolerance quantity: ";
 
           cin >> zeroInput;
 
           if (zeroInput < 0)
           {
              errorC = 1; //error logger
              errorHandling(); //recursion
           }
      }
 
      //if we don't want to write cout's again and again, we creat a function
      void firstQuiz::pointInput()
      {
           cout << "please enter the grade for student " << studentNo++ << " : ";
           cin >> point;
      }         
 
      //"everything is something happen" (sinyor terim)
      void firstQuiz::compute()
      {
                int zeroCount = 0;
                char closer;
                counterA = 0; avarageA = 0; maximumA = 0; minimumA = 100; 
                counterB = 0; avarageB = 0; maximumB = 0; minimumB = 100;
 
                //classic do-while structure
                do{
 
                pointInput();
 
                //when entered grade is negative and error handler is activated
                while(point<0 && zeroCount != zeroInput)
                {
                       zeroCount++;
                       cout << "negative! want to quit? (y / n) : ";
                       cin >> closer;
                       if (closer == 'y' || closer == 'Y')
                       {
                           break;
                       }
                       if( closer == 'n'  || closer == 'N')
                       {
                           pointInput();
                       }
                }           
                            //for above 50
                            if(point>50)
                            {
                                     counterA++;
                                     avarageA+=point;
                                     if(point > maximumA)
                                              maximumA=point;
                                     if(point < minimumA)
                                              minimumA=point;
                            }
 
                            //for belove 50
                            if(point<=50)
                            {
                                         //if it is negative, easily ignore that!
                                         if(point<0)
                                                    break;
                                         counterB++;
                                         avarageB+=point;
                                         if(point > maximumB)
                                                  maximumB=point;
                                         if(point < minimumB)
                                                  minimumB=point;
                            }
 
                }while(point>=0);
      }
 
      //compute avarages seperately
      void firstQuiz::computeAvarage()
      {
           avarageA = avarageA / counterA; //for above 50
           avarageB = avarageB / counterB; //for belove 50
      } 
 
      //result outputs
      void firstQuiz::printResult()
      {
           //+50
           cout << endl << "maximum (+ 50) is " << maximumA << endl;
           cout << "minimum (+ 50) is " << minimumA << endl;
           cout << "avarage (+ 50) is " << avarageA << endl << endl;
           //-50
           cout << "maximum (- 50) is " << maximumB << endl;
           cout << "minimum (- 50) is " << minimumB << endl;
           cout << "avarage (- 50) is " << avarageB << endl << endl;
      }