Цикл For внутри класса

#include<windows.h>
#include<stdlib.h>
#include<iostream.h>
#include<conio.h>
 
class student
{
public:
friend number;
char name;
char spec;
int year;
float medie;
void sravnenie(void);
void ustanov(void);
}
 
void student::ustanov()
{
int i,n,a,znak;
cout<<"Jelaemoe kolicestvo studentov?"<<endl;
cin>>n;
for(i=0;i<n;i++)
{
cout<<"Vvedite Imea"<<endl; cin>>znak[i]name;
cout<<"Vvedite specialinosti"<<endl; cin>>znak[i].spec;
cout<<"Vvedite god obucenia"<<endl; cin>>znak[i].year;
cout<<"Vvedite srednii bal"<<endl; cin>>znak[i].medie;}
getch();
}

#include<string.h>
#include<stdio.h>
#include<stdlib.h>
#include<iostream.h>
#include<conio.h>
 
class student
{
public:
friend number;
char name[100];
char spec[100];
char year[100];
int number;
float medie;
void sravnenie(void);
void ustanov(void);
void vivod(void);
}
znak[50];
 
void student::ustanov()
{
int i,n,a;
student b;
cout<<"Jelaemoe kolicestvo studentov?"<<endl;
cin>>n;
for(i=0;i<n;i++)
{
cout<<"Nomer "<<i+1<<" studenta"<<endl;
cin>>znak[i].number;
cout<<"Vvedite Imea"<<endl; cin>>name;
cout<<"Vvedite specialinosti"<<endl; cin>>spec;
cout<<"Vvedite god obucenia"<<endl; cin>>year;
cout<<"Vvedite srednii bal"<<endl; cin>>medie;
getch();
}
};
 
 
 
void student::vivod()
{
cout<<"Imea "<<name<<endl;
cout<<"Specialinosti "<<spec<<endl;
cout<<"God obucenia "<<year<<endl;
cout<<"Srednii bal "<<medie<<endl;
};
 
void student::sravnenie(void)
{
int a,b;
cout<<"Nomer 1 studenta"<<endl;
cin>>znak[a].number;
cout<<"Nomer 2 studenta"<<endl;
cin>>znak[b].number;
if(znak[a].medie>znak[b].medie)
{
cout<<"Student 1 imeet bal vishe"<<endl;}
else
cout<<"Student 2 ucitsea lucishe"<<endl;
}
getch();
 
 
 
 
int main()
{
student a;
int ok;
while(1)
{
clrscr();
cout<<"==Vibiraem cto delati=="<<endl;
cout<<"[1] Vvodim dannie \n"<<"[2] Vivodim dannie \n"
<<"[3] Sravnivaem dannie \n"<< "[0] Vihod iz programmi \n"<<"====================="<<endl;
cin>>ok;
switch(ok)
{
case 0: return(0);
case 1: a.ustanov(); getch();
case 2: a.vivod(); getch();
case 3: a.sravnenie();getch();
break;
}
};
}