c++ programme

[d1456]

guys i dont know what wrong with this prgramme , its a error free code
in output window its not displaying anything except that its making several code.cpp files in my folder

please help me





#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;
struct student //defining the structure student
{
string name;
int id;
float mark;
};
int readFile(student s[]) //function for reading file in the array
{
ifstream input("grades.txt"); //opening the file in read mode
int i=0; //for counting no of records in file
while(!input.eof())
{
input>>s[i].name>>s[i].id>>s[i].mark; //storing the information in array
i++; //incrementing i by 1
}
input.close(); //closing the file
return i; //returning the number of records stored in array
}
int menu() //for displaying the menu
{
cout<<"(1) Display students' details\n";
cout<<"(2) Calculate average of all students' marks\n";
cout<<"(3) Sort the students' details\n";
cout<<"(4) Search for a particular student's mark\n";
cout<<"(5) Find maximum\n";
cout<<"(6) Add new student to the record\n";
cout<<"(7) Quit program\n";
cout<<"Your choice: ";
int ch;
cin>>ch;
return ch; //returning the choice
}
void displayStudents(student s[],int n) //displaying the details of students
{
cout<<"\tName\t\tId\t\tMarks\n";
for(int i=0;i<n;i++) //looping through the array
{
cout<<"\t"<<s[i].name<<"\t\t"<<s[i].id; //displaying one by one
cout<<"\t\t"<<s[i].mark<<endl;
}
cout<<endl<<endl;
}
float calculateAverage(student s[],int n) //for calculating average marks
{
float avg=0; //for storing average
for(int i=0;i<n;i++)
avg+=s[i].mark; //adding all the marks to avg;
return avg/n; //returning average
}
bool compare1(student s1,student s2) //comparator for sorting according to name
{
return s1.name<s2.name;
}
bool compare2(student s1,student s2) //comparator for storing according to marks
{
return s1.mark<s2.mark;
}
void sortName(student s[],int n) //sorting according to names
{
sort(s,s+n,compare1); //calling sort function
}
void sortMarks(student s[],int n) //sorting according to marks
{
sort(s,s+n,compare2); //calling sort function
}
int searchMarks(student s[],int n,string m) //searching for a particular student's marks
{
int index=-1; //initialising index to 1
for(int i=0;i<n;i++)
{
if(s[i].name==m) //if this student's name is same as m
{
index=i; //then index becomes i
break;
}
}
return index; //returning the index
}
float findMaximum(student s[],int n) //finding maximum marks
{
float m=s[0].mark;
for(int i=1;i<n;i++) //looping through the array to compare the marks with m
m=max(m,s[i].mark);
return m; //returning m
}
int updateFile(student arr[]) //for updating file
{
ofstream output("grades.txt",ios::app); //opening file in append mode
student s;
//Taking student's details from user
cout<<"Student's name: ";
cin>>s.name;
cout<<"Student's Id: ";
cin>>s.id;
cout<<"student's marks: ";
cin>>s.mark;
output<<endl<<s.name<<" "<<s.id<<" "<<s.mark; //storing details in file
output.close();
int n=readFile(arr); //calling readFile() function
cout<<endl<<endl;
return n; //returning the updated value of size of array
}
int main()
{
student studentArray[100]; //declaring array of type student
int n=readFile(studentArray); //calling readInput function
int ch=0; //for storing choice
while(ch!=7) //looping till choice becomes 7
{
ch=menu(); //calling menu function
switch(ch)
{
case 1:displayStudents(studentArray,n); //if ch=1, then displaying students' records
break;
case 2: //if ch=2, then displaying the average marks
cout<<"Average marks are "<<calculateAverage(studentArray,n)<<endl<<endl<<endl;
break;
case 3: //if ch=3, then sorting the array
{
cout<<"According to (n)ame or (m)arks: ";
//if user enters n,then sorting according to name
//if user enters m, then sorting according to marks
char s;
cin>>s;
if(s=='n')
sortName(studentArray,n);
else
sortMarks(studentArray,n);
cout<<"done\n\n";
}
break;
case 4: //if ch=4, then finding the marks of particular student
{
cout<<"Name of the student : "; //asking the user for the student's name
string k;
cin>>k;
int m=searchMarks(studentArray,n,k); //searching for the marks of that student
if(m==-1) //if index is -1 then record not found
cout<<"Record not found\n\n\n";
else //otherwise displaying the marks
cout<<"Marks of this student are "<<studentArray[m].mark<<endl<<endl<<endl;
}
break;
case 5: //if ch=5, then displaying the maximum marks
cout<<"Maximum marks are "<<findMaximum(studentArray,n)<<endl<<endl<<endl;
break;
case 6: //if ch=6, then updating the file
n=updateFile(studentArray);
break;
case 7: //if ch=7, then quitting the program
cout<<"Goodbye\n";
break;
}
}
return 0;
}



these are the grades
grades.txt
Alex 123 60.75
Peter 122 54.50
Maria 111 75.25
Mary 101 65.00
Rocky 144 95.5

[Thomas1965]

In your readFile funtion you need to check if the file is open before you use it.

int readFile(student s[]) //function for reading file in the array
{
  ifstream input("grades.txt"); //opening the file in read mode
  if (!input)
  {
    perror(nullptr); // #include <cstdio>
    return 1;
  }
  // ...
}