Help me to show step by step solution infix to postfix

the code is running but my professor told me to modify the code. he need to see the step by step conversion of infix to postfix. the problem is i don't know how to show the step by step conversion..
example:
(a+b )/(a-b )
a+b / a-b
a+b a-b/
ab+ ab-/

#include <iostream>
#define STACK_SIZE 100
using namespace std;

char stackChar[STACK_SIZE];
int top=-1;

void push(char c);
char pop();

int main()
{
	 
	
	char expr[STACK_SIZE], postfixexpr[STACK_SIZE];
	cout << "Enter the exp<b></b>ression: ";
	cin.getline(expr,STACK_SIZE);
	
	strcat(expr,")");
	push('(');
	
	int j=0; 

	for(int i=0;i<strlen(expr);i++)
	{
		if(isalnum(expr[i]))
			postfixexpr[j++]=expr[i];
		else if(expr[i]==')')
		{
			while(stackChar[top]!='(')
				postfixexpr[j++]=pop();
			pop();
		}
	
		else if(expr[i]=='+' || expr[i]=='-')
		{		
			while(stackChar[top]=='*' || stackChar[top]=='/' || stackChar[top]=='^' || stackChar[top]=='+' || stackChar[top]=='-')
				postfixexpr[j++]=pop();
			push(expr[i]);
		}

		
		else if(expr[i]=='*' || expr[i]=='/')
		{
			while(stackChar[top]=='^' || stackChar[top]==expr[i])
				postfixexpr[j++]=pop();
			push(expr[i]);
		}
		else
			push(expr[i]);
	}
	
	postfixexpr[j]='\0';

	cout << postfixexpr;
	system("pause>0");
	return 0;

}


void push(char c)
{
	stackChar[++top] = c;
}

char pop()
{
	return stackChar[top--];
}