String Recognition 2

/* String Recognition */

#include<stdio.h>
#include<conio.h>
#include<iostream.h>
#define SIZE_OF_STACK 30 //Number of slots in Stack

char alphabet[50];
int count=0;
class stack
{
 private:
	char slot[SIZE_OF_STACK];
	int TOP;
 public:
	stack()
	{
	 TOP=-1;
	}

	int PUSH(char item)
	{
		 if(TOP==SIZE_OF_STACK-1)
		 {
			return 0; // Push Operation Unsuccessful
		 }
		 else
		 {
			  TOP++;
			  slot[TOP]=item;
			return 1; // Push Operation Successful
		 }
	}

	char POP(void)
	{
		if(TOP==-1)
		{
			return -1;
		}
		else
		{
		 TOP--;
		 return slot[TOP+1];
		}
	}

	void PEEP(int slot_number)
	{
		 slot_number=slot_number-1;

		 if(slot_number>TOP&&slot_number<=SIZE_OF_STACK-1)
		 {
		  cout<<endl<<"ERROR : Item does not exist ! Last item is at Slot "<<TOP+1;
		 }
		 else if(slot_number<0)
		 {
		  cout<<endl<<"ERROR : Enter a valid Slot Number !";
		 }
		 else if(slot_number>SIZE_OF_STACK-1)
		 {
		 cout<<endl<<"ERROR : Slot number beyond bounds of stack ! Size of Stack is "<<SIZE_OF_STACK;
		 }
		 else
		 {
		  cout<<slot[slot_number];
		 }
	}

	int get_top()
	{
	 return TOP;
	}
};

void main()
{
 clrscr();
 stack s;
 int no_of_alphabets=0;
 int check_alphabet(char);
 char next_alphabet(void);
 char temp;
 do
 {
	 cout<<"How many alphabets does the language contain? : ";
	 cin>>no_of_alphabets;
	 if(no_of_alphabets<=0)
	 {
		cout<<endl<<"ERROR : Enter a valid number (>0) !"<<endl<<endl;
	 }
 }while(no_of_alphabets<=0);

 for(int i=0;i<no_of_alphabets;i++)
 {
	cout<<endl<<"Alphabet "<<i+1<<" : ";
	temp=getch();
	putchar(temp);
	if(check_alphabet(temp)==0)
	{
		cout<<"   ERROR : Character already exists in the language !";
		i--;
	}
	else
	{
		alphabet[i]=temp;
		count++;
	}
 }
 alphabet[i]='\0';

 getch();

}

int check_alphabet(char x)
{
 for(int i=0;i<count;i++)
 {
	if(x==alphabet[i])
	{
		return 0; // Character Repeated
	}
 }
 return 1;
}

char next_alphabet(void)
{
 static int number=0;
 number++;
 return alphabet[number];
}