Infix to Post fix conversion Program in c++

Program name: program to convert infix expression to post fix

Program description: A program which convert infix to postfix using stacks as data structure in c++ 

// data_assigment.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "iostream"
#include "conio.h"
using namespace std;
class postfix{
private:
 char value[50];
 char value2[50];
 char stack[20];
 char temp[20];
 char head;
 int top;
 int temp_top;
 int j;
public:
 postfix(){
 strcpy(value,"");
 strcpy(stack,"");
 strcpy(temp,"");
 head='/0';
 top=-1; 
 temp_top=0;
 j=0;
 }
 void scan();
 void input();
 void push(char);
 void pop();
 void result();
};
void postfix::pop(){
 if(top==-1)
  cout<<"Stack is empty";
 while(top!=-1){
 if(head==')')
  {cout<<stack[top];
 value2[j]=stack[top];
  j++;
 top--;
 if(stack[top]=='(')
  {top--;
 break;}
 }
 else
 {
  cout<<stack[top];
  value2[j]=stack[top];
  j++;
  top--;
  if(stack[top]=='(')
   break;
 }
 }//while end
}
void postfix::push(char temp){
 if(top==19)
 cout<<"stack is full";
 top++;
 stack[top]=temp;
}
void postfix::input(){
 cout<<"\n\t      Program to convert Infix to Post fix";
 cout<<"\n\nEnter expression in InFix form =  ";
 cin>>value;
 cout<<"\nThe expression in post fix form is = ";
}
void postfix:: scan(){
 int i=0;
 while(1){
  head=value[i];
  if(head==NULL)
   break;
  i++;
  if( head=='(' || head=='*'|| head=='/'||head=='+' || head=='-'||head==')')
  {
  if(head=='(')
   push(head);
  else if(stack[top]=='(')
   push(head);
  else if(head==')')
   pop();
  else if ((stack[top]=='+' || stack[top]=='-') && (head=='*' || head=='/' ) )
   push(head);
  else if (top==-1)
   push(head);
  else
  {
  pop();
  push(head);}
  }

  else
  {cout<<head;temp[temp_top]=head;
  temp_top++;
  value2[j]=head;
  j++;
  }
 
 }
  pop();
  value2[j]=NULL;
  j++;
}
void postfix::result(){
 int counter=0,final[20],top_final=-1,answer=0,check=0,answer2=0;
 cout<<"\n\nNow Enter the values for variables."<<endl;
 for(int i=0;i<20;i++) 
 {
  head=value2[counter];
  if(head==NULL)
   break;
  switch(head){
   case '+':
    answer=final[top_final]+final[top_final-1];
    answer2=answer;
    top_final--;
    final[top_final]=answer;
    check++;
    break;
   case '-':
    answer=final[top_final-1]-final[top_final];
    answer2=answer;
    top_final--;
    final[top_final]=answer;
    check++;
    break;
   case '*':
    answer=final[top_final]*final[top_final-1];
    answer2=answer;
    top_final--;
    final[top_final]=answer;
    check++;
    break;
   case '/':
    answer=final[top_final-1]/final[top_final];
    answer2=answer;
    top_final--;
    final[top_final]=answer;
    check++;
    break;
   default:
    break;
}  
  if(head!='+'||head!='*'||head!='-'||head!='/')
  {
  if(i<temp_top){
  cout<<"Enter value for "<<temp[counter]<<" = ";
  top_final++;
  cin>>final[top_final];
  }
  }
  counter++;
 }
 if (check<=1)
cout<<"The answer is="<<answer2;
 else
  cout<<"The answer is="<<answer;
  }
int _tmain(int argc, _TCHAR* argv[])
{
 postfix object;
 object.input();
 object.scan();
 object.result();
 getch();
 return 0;
}