4-) Below is a program written in order to perform a task, trace the program and provide comments for the code. In a few sentences, describe what does the program do? and show the result of the...

#include

#include

#include

using namespace std;

#define maxchars 100//

int main()

{

      char input_str[maxchars+1], *p;

      stack num_stack;

      int c;

      double a, b, n;

      cout < "enter="" string:="">

            cin.getline(input_str, maxchars);

      p = strtok(input_str, " ");

      while (p)

      {

            c = p[0];

            if (c == '+' || c == '*' || c == '/' || c == '-')

            {

                  if (num_stack.size() <>

                  {

                        cout < "error:="" too="" many="" ops."=""><>

                        system("pause");

                        return -1;

                  }

            b = num_stack.top();

            num_stack.pop();

            a = num_stack.top();

            num_stack.pop();

            switch (c)

            {

            case '+': n = a + b;

                  break;

            case '*': n = a * b;

                  break;

            case '/': n = a / b;

                  break;

            case '-': n = a - b;

                  break;

            }

            num_stack.push(n);

      }

      else

      {

            num_stack.push(atof(p));

      }

      p = strtok(NULL, " ");

}

cout < "the="" answer="" is:="" "="">< num_stack.top()=""><>

      system("pause");

      return 0;

}