Class to calculate the number and average of students

#include<iostream.h>
#include<conio.h>
#include<string.h>
#include<stdio.h>
class stu
 {
private:
int adm_no;
int roll;
float mks;
char name[100];
float avg;
int a;
public:
void getdata();
void putdata();
void c();
 };
void stu::getdata()
{

cout<<"enter the name/n";
gets(name);
cout<<"enter roll no/n";
cin>>roll;
cout<<"enter adm no./n";
cin>>adm_no;
cout<<"enter cs marks/n";
cin>>mks;
}
void stu::putdata()
{
cout<<" name\n";
puts(name);
cout<<" roll no\n";
cout<<roll;
cout<<" adm no\n";
cout<<adm_no;
cout<<" cs marks\n";
cout<<mks;
}
 void stu::c(int n)
{
a=n;
float sum=0;
for(int i=0;i<a;i++)
  {
sum=x[i]+sum;

  }
  float avg=sum/a;
  cout<<"average/n"<<avg;
}

 void main()
 {
clrscr();
stu x;
int i;
float r;
for(i=0;i<51;i++)
{
x[i].getdata();

}
for(i=0;i<51;i++)
{
x[i].putdata();
}
      x.c(51);
getch();
 }