Procedure RENEWING_A_BOOK
{
   /* to disable printing out report when book hasn't been renewed */
   set renew_flag as false;

   while(CANCEL button not pressed)
   {
     if(OK button pressed)
     {
       read in Call_Number from the text-box;
       checks for syntax error on Call_Number;

       if(syntax error on Call_Number occurred)
       {
         display error message(syntax error occurred);
         set renew_flag as false; /* to disable printing out report */
       }
       else /* no syntax error */
       {
         if(Call_Number doesn't exist in database)
            display error message(call number doesn't exist);
         else if(Circulation_Status is On_Hold)
         {
           display error message(The book cannot be renewed - there exists a holder);
           open new pop-up window displaying a holder's information;

           if(PRINT button pressed) 
              print out the holder's information;
           else /* CLOSE button */ 
              close current window;

           update Circulation_Status as On_Loan in database;
           update Loans.User_ID as a holder and Loans.Loan_Date as today for book copy with Call_Number in database;
         }
         else if(Circulation_Status is On_Loan or overdue)
         {
           if(customer is Restricted)
           {
             display message(cannot be renewed - fines exceeds
             the maximum amount allowed);
             update Circulation_Status as Available in database;
           }
           else
           {
             update Loan_Date as today in database;
             display message(the book successfully renewed);
             set renewed_flag as true; /* to enable printing out report */
           }
         }

         else /* Circulation_Status is Available or Out_of_Circulation */
           display error message(The book is not on loan);
       }
     }

     else if(PRINT_REPORT button pressed)
     {
       if(renewed_flag is true) 
           print out customer, book copy, library information;
       else 
           display error message(book hasn't been renewed - enter new call number);
     }
     else if(CLEAR button pressed) 
       clear the contents in the entry field;
     else /* HLEP button */
     {
       open new pop-up window displaying help;
       if(CLOSE button pressed) close help window;
     }
   }
}