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#pragma hdrstop               //ASSIGNMENT 2, TASK 2  JANE JAKEMAN
#pragma argsused              //DATE COMPLETED 16 JAN 2006
#include <conio.h>            //PROGRAM GETS A NUMBER, VALIDATES, CALCULATES
#include<iostream.h>          //AND OUTPUTS WHETHER VALID OR NOT WITH A CHOICE
#include<ctype.h>             //TO CONFIRM DATA ENTRY, AND LOOP TO CONTINUE
#include <stdio.h>            
#include <iostream>           //FILENAME: A2T2ISBNNumbers

using namespace std;      //used with converting character to integer
  char ISBN[11];          //ISBN to hold char array
  char ch;                //ch to input char,put in array
  int loop=0;             //used for loop
  int x=0;                //used for loop
  int y=10;               //used for multiplication loop  (ten, down to 1)
  int total=0;            //used to hold result of ISBN calc
  int ans=0;              //used to hold the answer to checksum
  int check;              //used to hold ans divided by 11 to checksum
  const int d=11;         //used to allocate 11 as constant
  char ynone, yntwo;      //used for two Y/N requests
  char quit;              //used to close program

void getISBN (void);                             //declare prototype of getISBN
void correctno(void);                            //declare prototype is no correct?
void calculate (void);                           //declare prototype of calculate
void yesno (void);                               //declare prototype of yesno
void close (void);                               //declare prototype to close

void main(void)                                  //start of main
{                                                //open main
  getISBN();                                     //call functions in order
  correctno();
  calculate();
  yesno();
  close();
 

}                                                 //close main
//FUNCTION GET ISBN
void getISBN(void)                                        //start of code for function getISBN
{                                                         //open getISBN
     loop=0;                                              //set loop to 0
     cout<<"\n\nPlease enter the ISBN number\n";            //ask user for input
  do                                                      //start of do
  {                                                       //open do
     ch=getch();                                          //get character, put it in ch
    if ((ch>='0'&&ch<='9')||((ch=='x')||(ch=='X')))       //validate input
    {                                                     //open if
     ISBN[loop]=ch;                                       //put character in ISBN[0]
     loop++;                                              //add 1 to loop, will fill array
    }                                                     //close if
  }while(loop<10);                                        //while condition, fills array toISBN[9]
    ISBN[10]='\0';                                        //ends array
    cout<<"\n\nThe number you entered is :  " <<ISBN<<endl; //outputs validated array
    correctno();                                          //call function, correct no
}                                                         //end of function getISBN
//FUNCTION IS NUMBER CORRECT?
void correctno(void)                                      //start function check if no is correct
{                                                         //open function
      ynone='0';                                          //set ynone to character 0
   while (ynone!='Y'||'y'||'N'||'n')                      //while condition
   {                                                      //open while
      cout<<"\n\nIs the ISBN number correct? Y : N ";     //ask for input
      ynone = getch();                                    //input y or n
     if(ynone=='Y'||ynone=='y')                           //if yes
     {
      clrscr();                                            //open if
      calculate();                                        //call function calculate
     }                                                    //close if
     if(ynone=='N'||ynone=='n')                           //if no
     {
      getISBN();                                          //go and input the number again
     }
     if(ynone!='Y'||'y'||'N'||'n')                        //if not n or y
     {
      cout<<'\7';                                         //beep
      cout<<"........please enter Y / N \n";
     }                                                    //close if
   }                                                      //close while
}                                                         //close function
//FUNCTION CALCULATE
void calculate(void)                                      //function to calculate
{                                                         //open function
    x=0;                                                  //set loop to 0
    while (ISBN[x] != '\0')                               //While the string isn't at the end...
    {                                                     //open while
        int(ISBN[x]-48);                                  //Convert ISBN[0]char to int
        x++;                                              //move along array by 1
        if (ISBN[9]==120)                                 //calc to convert x to ascii, then to 10
        ISBN[9]=58;
        if (ISBN[9]==88)                                  //calc to convert X to ascii, then to 10
        ISBN[9]=58;                                       //therefore - 48 as with rest of array = 10
        }                                                 //set x to 0
        x=0;                                              //while not at end of string
    while (ISBN[x] != '\0')                               //open while
    {                                                     //output number as integer
       total = int ((ISBN[x]-48)*y);                      //multiply first by 10, put in total
       ans = ans + total;                                 //put total in ans at each loop
       x++;                                               //move along array by 1 each time
       y--;                                               //multiply by 1 less each time
     }                                                    //end while
      check=ans%d;                                        //divide by constant 11, get remainder
     if (check==0)                                        //if no remainder
      cout<<"\n\nThe ISBN Number is valid\n";             //ISBN valid
     if(check!=0)                                         //if there is remainder
      cout<<"\n\nISBN Number is not valid!\n";            //ISBN not valid
      yesno();                                            //call next function
}
//FUNCTION ASKING CONTINUE Y/N?
void yesno (void)                                                   //function Y/N to continue
{                                                                   //open function
    do
     {
       cout<<"\nDo you wish to enter another number? Y : N \n";     //ask user for input
       yntwo=getch();                                               //get y or n
      if (yntwo=='Y'||yntwo=='y')                                   //if yes
       getISBN();                                                   //go to function getISBN
      if(yntwo=='N'||yntwo=='n')                                    //if no,
       close();                                                     //go to function close
       cout<<'\7';                                                  //sound beep
     }while(yntwo!='Y'||'y'||'N'||'n');                             //while not yes or no
}
//FUNCTION TO CLOSE
void close(void)
{                                                                   
 clrscr();                                                          //clear screen
 ynone=='Y';                                                        //set so while won't loop
 yntwo=='Y';
 cout<<"\n\nThank you for using this program";                      //output close message
 getchar();
}
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