Postfix expression evaluation

#include<iostream.h>
#include<conio.h>
#inlcude<math.h>
#include<ctype.h>
clss post 
{
private:
char exp[50];
public:
void getdata()
{
cout<<"\n\n\t the postfix evaluation:";
cin>>exp;
}
void putdata();
float calc(float,float,char);
};
void post::putdata()
{
int i=0,top=0;
float stk[50];
cahr item;
while(exp[i]!='\0')
{
item=exp[i];
if(isalapha(item))
{
cout<<"item<<":";
cin>>stk[++top];
}
else
{
float v1=stk[top--];
float v2=stk[top];
stk[top]=calc(v2,v1,item);
}
i++;
}
cout<<"\npostfix evaluation:"<<stk[top];
}
float post::calc(float a,float b,char c)
[
float res;
switch(c)
{
case'+':
res=a+b;
break;
case'-':
res=a-b;
break;
case'*':
res=a*b;
break;
case'/':
res=a/b;
break;
case'^':
res=pow(a,b);
break;
}
return(res);
}
void main()
{
clrscr();
cout<<"\n\tPOSTFIX EXPRESSION EVALUATION\n";
cout<<"\n\t****************************\n";
post p;
p.getdata();
p.putdata();
getch();
}

POSTFIX EXPRESSION EVALUATION

Input:
the postfix evaluation:ab+c-
 a:6
 b:3
 c:2

Output:
postfix evaluation:7