EVALUATI.BAK

#include<iostream.h>
#include<conio.h>
#define max 20
#include<string.h>

float stack[max];
int top=-1;
void push(float x)
{
   if(top==(max-1) )
     cout<<"Overflow";
   else
    {
       stack[++top]=x;
    }
}
float pop()
{
    if(top==-1)
    { cout<<"Invalid expression";
     return -1;
    }
    else
     return (stack[top--]);
}

void main()
{
 char a[]={"231*+9-d"};
 int i,j,p1,p2;
 float e1,e2,sum;
 int s=sizeof(a)/sizeof(a[0]);
  clrscr();
 s=s-1;
 for(i=0;i<s;i++)
 {
    if(a[i]>='0' && a[i]<='9')
    {
      push(a[i]-'0');
    }
    else if(a[i]=='*')
     {
       e2=pop();
       e1=pop();
       push(e1*e2);
     }
     else if(a[i]=='+')
     {
       e2=pop();
       e1=pop();
       sum=e1+e2;
       push(sum);
     }
	else if(a[i]=='-')
     {
       e2=pop();
       e1=pop();
       push(e1-e2);
     }
	else if(a[i]=='/')
     {
       e2=pop();
       e1=pop();
       push(e1/e2);
     }
	else if(a[i]=='^')
     {
       p1=pop();
       p2=pop();
       push(p2^p1);
      }
     else
     cout<<"Error in expression\n";
 }
   cout<<"Value="<<stack[top];
   getch();
 }