stack implementation program in c++

#include<iostream.h>
#include<conio.h>
#include<process.h>

int stack[50],top=-1,item,n,i,size;

class stack1
{
public:
void push()
{

if(top==size-1)
{
cout<<"\n no more items can be pushed\n";
}
else
{
cout<<"enter the item to be pushed\n";
top++;
cin>>item;
stack[top]=item;
}
}


void pop()
{
if(top==-1)

cout<<"\nstack underflow\n";
else
{
cout<<"the item deleted is \t"<<stack[top];
top--;
}}

void stacktop()
{
if(top==-1)
cout<<"\nstack underflow\n";
else
cout<<"the top of the stack is "<<stack[top];
}

void clearstack()
{

if(top==-1)
cout<<"\n0 items in stack\n";
else
{
for(i=top;i>=0;i--)
stack[i]='\0';
top=-1;
}
}



void display()
{
if(top==-1)
cout<<"\n 0 items in stack\n";
else
{
for(i=top;i>=0;i--)
cout<<stack[i]<<"\n";
}
}
};

void main()
{
clrscr();
int a,b=1;
stack1 s;
cout<<"enter the size of the stack\t";
cin>>size;
while(b==1)
{
clrscr();
cout<<"\nMAIN MENU\n";
cout<<"\n1.push\n"<<"2.pop\n"<<"3.stack top\n"<<"4.clearstack\n"<<"5.display\n"<<"6.exit\n";
cout<<"\nenter your choice\t";
cin>>a;
switch(a)
{
case 1:s.push();
break;

case 2:s.pop();
break;

case 3:s.stacktop();
break;

case 4: s.clearstack();
cout<<"\nthe stack has been cleared\n";
break;

case 5: s.display();
break;
default:
cout<<"\nwrong choice\n";

case 6: exit(0);
break;


}
cout<<"\npress 1 to go to main menu or 0 to exit\n";
cin>>b;
}
}