#include<iostream>
#include<math.h>
using namespace std;

const int rec=300;
int istuid[rec];//student id
float fmark[rec];//student mark

void vinput(int & i);
void vdisplay(int & i);

int main(void)
{
    int i=0;
    vinput(i);
    vdisplay(i);
    system("pause");
}

void vinput(int & i)
{
     char yn; //variable for yes or no
     while (!cin.eof() && i < rec)
     {
           cin >> istuid;
           if (cin.eof()){i++;continue;} 
           else if (!(istuid < 999999 && istuid > 0))
           {
                cout << "Error, Student ID is invalid\n"
                     << "Do you still want to display the result(Y/N)";
/***********************************************
ERROR here
after running this line, it skips the "cin" >_<
***********************************************/
                cin >> yn;
                if (yn != 'y' || yn != 'Y')
                {
                    cout << "\nprogram terminates, ";
                    system("pause");
                    exit(1);
                }
                break;
           }
           cin >> fmark;
           if (cin.eof()){i++;continue;}
           else if (!(fmark < 100 && fmark > 0))
           {
                cout << "Error, Student mark is invalid\n"
                     << "Do you still want to display the result(Y/N)";
                cin >> yn;
                if (yn != 'y' || yn != 'Y')
                {
                    cout << "\nprogram terminates, ";
                    system("pause");
                    exit(1);
                }
                break;
           }
     i++; //i plus plus here, its not showing i dono why
     }
}

void vdisplay(int & i)
{
     int pert=0;
     double average=0,subtra,sd=0,sump=0;
     
     //finding how many records and average
     for (int j = 0; j < i; j++)
     {
         if (fmark[j])
         {
         pert++;
         average += fmark[j];
         }
     }
     if (pert > 0)
     {
          average = average / pert;
          cout << "Pertinent records:\t" << pert <<"\n";
          cout << "Mean or average:\t" << average <<"\n";
     //end number of records & average
     
     //start loop again for standard deviation
          for (int j = 0; j < i; j++)
          {
              if (fmark[j])
              {
              subtra = fmark[j] - average;
              sump += pow(subtra, 2);
              }
          }
          sd = sump / pert;
          sd = sqrt(sd);
          cout << "Standard deviation:\t" << sd <<"\n\n";
     //end finding standard deviation
     
     //loop last time for displaying records
          for (int j = 0; j < i; j++)
          {
              if (fmark[j])
              {
              cout << istuid[j] << "\t" <<fmark[j] << "\n";
              }
          }
     }
}

                if(yn != 'y' || yn != 'Y')                {                    cout << "\nprogram terminates, ";                    system("pause");                    exit(1);                }

                if(yn != 'y' && yn != 'Y')                {                    cout << "\nprogram terminates, ";                    system("pause");                    exit(1);                }

void pause(){	// wait for enter	char a;	std::cin >> a;}

#include<iostream>#include<math.h>using namespace std;const int rec=300;int istuid[rec];//student idfloat fmark[rec];//student mark// Why are you limiting things this way, and adding the complexity of having to// count the records yourself?void vinput(int & i);void vdisplay(int & i);// what the hell does the v stand for? Also, why are you using the parameter for// a function return value, instead of, well, the return value?int main(void){    int i=0;    vinput(i);    vdisplay(i);    system("pause");}void vinput(int & i){     char yn; //variable for yes or no     while (!cin.eof() && i < rec)     {           cin >> istuid;           if (cin.eof()){i++;continue;}           // Why "continue" for a loop that you would then break out of            // immediately? Also, why are you "counting up a record" when the           // input failed? Also, what do you want to do if the input is           // not a number at all?           else if (!(istuid < 999999 && istuid > 0))           {                cout << "Error, Student ID is invalid\n"                     << "Do you still want to display the result(Y/N)";/***********************************************ERROR hereafter running this line, it skips the "cin" >_<***********************************************/                cin >> yn;                if (yn != 'y' || yn != 'Y') // noted logic error here                {                    cout << "\nprogram terminates, ";                    system("pause");                    exit(1);                }                break;           }           cin >> fmark;           // Have you not noticed the duplication here? Think about functions           // in terms of organization, avoiding repetition in the code, and            // representing a logical task - not simply in terms of cutting up           // a long procedure.           if (cin.eof()){i++;continue;}           else if (!(fmark < 100 && fmark > 0))           {                cout << "Error, Student mark is invalid\n"                     << "Do you still want to display the result(Y/N)";                cin >> yn;                if (yn != 'y' || yn != 'Y')                {                    cout << "\nprogram terminates, ";                    system("pause");                    exit(1);                }                break;           }     i++; //i plus plus here, its not showing i dono why     }}void vdisplay(int & i){     int pert=0;     double average=0,subtra,sd=0,sump=0;     // In C++, you should scope your variables as tightly as possible to avoid     // name collisions; this also means putting them near first use in the same     // scope (since they need not be declared at the top of their scope).     //finding how many records and average     for (int j = 0; j < i; j++)     {         if (fmark[j])         {         pert++;         average += fmark[j];         }     }     if (pert > 0)     {          average = average / pert;          cout << "Pertinent records:\t" << pert <<"\n";          cout << "Mean or average:\t" << average <<"\n";     //end number of records & average          //start loop again for standard deviation          for (int j = 0; j < i; j++)          {              if (fmark[j])              {              subtra = fmark[j] - average;              sump += pow(subtra, 2);              }          }          sd = sump / pert;          sd = sqrt(sd);          cout << "Standard deviation:\t" << sd <<"\n\n";     //end finding standard deviation          //loop last time for displaying records          for (int j = 0; j < i; j++)          {              if (fmark[j])              {              cout << istuid[j] << "\t" <<fmark[j] << "\n";              }          }     }}

#include<iostream>#include<math.h>#include<vector>#include<string>using namespace std;struct studentRecord {  int id;  float mark;}; // if you were really lazy, you could make use of std::pair instead// To avoid extra prototyping effort, I put the helper functions before main.// Utility to grab a whole line of text from the user (I assume the program will// only be run interactively) and toss away garbage at the end of the line (so// that it will not be seen by subsequent reads of cin).template<typename T>bool getInput(T& input) {  cin >> input;  // The reading will fail on EOF, invalid input, etc. Check if successful.  bool result = (bool)cin;  // "reset" cin for the next read whether or not this one failed - unless we  // reached eof.  if (!cin.eof()) {    cin.reset();    cin.ignore(numeric_limits<streamsize>::max(), '\n');  }  return result;}template<typename T>bool isValid(T provided, T minimum, T maximum) {  return (provided <= maximum && provided >= minimum);  // I think your version had a logic error too; consider the edge cases.}// Give the user the option to terminate the program.template<typename T>void promptForTermination(std::string nameOfThing) {  cout << "Error, " << nameOfThing << " is invalid\n"       << "Do you still want to display the result(Y/N)" << endl;  // The missing "endl" in your code might also be problematic.  std::pair<char, bool> prompt = getInput<char>();  if (prompt != 'y' && prompt != 'Y') {    cout << "\nprogram terminates. "; // fixed comma -> period    system("pause");    exit(1);  }}vector<studentRecord> getRecords() {  vector<studentRecords> results;  while (!cin.eof()) {    studentRecord current;    // Try to read studentID; if there's a problem, prompt for termination.    int studentId;    if (getInput(studentId) && isValid(studentId, 1, 999999)) {      // We successfully read a student ID which is in range.      current.id = studentId;    } else {      promptForTermination("Student ID");      continue; // don't ask for a mark for this invalid ID, or store it.    }    // Similarly for the mark. There's still some duplication here. Think about    // what you might do about it.    float studentMark;    if (getInput(studentMark) && isValid(studentMark, 0.0, 100.0)) {      current.mark = studentMark;    } else {      promptForTermination("Student mark");      continue; // don't store this record, because mark is invalid.    }    // We have a valid record (ID and mark).    results.push_back(current);  }  return results;}void displayStats(const vector<studentRecord>& data) {  // Count pertinent records and get running sum.  // TODO: don't store pertinent records.  // Is a record with a mark of exactly 0.0 supposed to be valid (though  // ignored for statistics)?  float sum = 0;   int pertinentRecords = 0;  int totalRecords = data.size();  for (int i = 0; i < totalRecords; i++) {    float currentMark = totalRecords.mark;    if (currentMark) {      pertinentRecords++;      sum += currentMark;    }  }  if (!pertinentRecords) return; // no stats.  int average = sum / pertinentRecords;  cout << "Pertinent records:\t" << pertinentRecords << "\n"       << "Mean or average:\t" << average << endl;    // Dear Professor:  // If you are reading these comments, it indicates that the student has   // blindly copy-and-pasted this code from a message board. If this has   // happened I can only offer you my assurance that it was unintentional on my  // part (I no longer attend any university, much less the student's). The code  // provided was basically intended to illustrate several possible refactorings  // and elements of good C++ style; it is based off of code which he posted  // which was nearly working, but, in my honest opinion, quite awful.  // start loop again for standard deviation  float squaredError;  for (int i = 0; i < totalRecords; i++) {    float currentMark = totalRecords.mark;    if (currentMark) {      float difference = currentMark - average;      squaredError += (difference * difference);    }  }  float rootMeanSquared = sqrt(squaredError / pertinentResults);  cout << "Standard deviation:\t" << rootMeanSquared <<"\n\n";  //end finding standard deviation  // For what it is worth, my experience with learning C++ in university (to  // be fair, it was five or six years ago) was that the curriculum does not  // cover many aspects of modern C++ style - in particular, use of the Standard  // Library - which are essential to writing good C++ code. The original code  // did indeed properly refer to <iostream> instead of the deprecated  // <iostream.h>, and demonstrated awareness of the existence of the std  // namespace, but made no reference to the excellent (and very appropriate  // here) library classes std::vector and std::string.   //loop last time for displaying records  for (int i = 0; i < totalRecords; i++) {    float currentMark = totalRecords.mark;    if (currentMark) {      cout << totalRecords.id << "\t" << currentMark << endl;    }  }  // I therefore exhort you to ensure that this material is covered in this  // student's course, in the future if not now - please, pull any   // administrative strings necessary to ensure this happens. I appeal to your  // interest in the proper education of these young minds - today's university  // students represent the future, as I am sure you are aware (I do not  // actually know what university you are teaching at, but the one I went to  // made a great deal about emphasizing this fact in its PR material).  // In any event, please contact me at karl DOT knechtel AT utoronto DOT ca (I  // retain the email address as an alumnus).}int main() {  displayStats(getRecords());  system("pause");}