[HELP] ISBN Check Digit

Code:

---

#include <iostream.h>
#include <conio.h>
#include <stdio.h>
#include <string.h>

int main()

{
    char cISBN[10];
    int i,iLen,iNNF,iISBN[9],iTotal,iCheck;
   
    for(i=0;i<10;i++)
    {
                    cISBN[i]='\0';
    }
                   
                    printf("Enter ISBN ");
                    gets(cISBN);
                    iLen=strlen(cISBN);
                   
                    if(iLen!=9)
                    {
                                printf("ISBN length error ");
                    }
                               
                                else
                                {
                                    iNNF=0;
                                    for(i=0;i<iLen&&iNNF==0;i++)
                                    {
                                                              if((cISBN[i]<0)||(cISBN[i]>9))
                                                              {
                                                                                  printf("ISBN numerical error ");
                                                                                  iNNF=1;
                                                              }
                                                                                 
                                                                                  else
                                                                                  {
                                                                                      iTotal=0;
                                                                                      iISBN[i]=cISBN[i]-48;
                                                                                      iTotal=iISBN[i]*(i+1);
                                                                                  }
                                    }
                                }
                                                                                     
                                                                                      iCheck=0;
                                                                                      iCheck=iTotal%11;
                                                                                      cout<<(iCheck);
                                                                                     
                                                                                      getch();
}

---

Error 1 (gone): if(cISBN[i]<0||>9) /*expected primary-expression before '>' token*/
thanks Adak and MK27.

Error 2:
input 013190190
output 7 (should be)

But it gave me "ISBN numerical error 10" or "ISBN length error 10" as output instead, I don't know where the 10 came from, try run it...

if(cISBN[i]<0||>9) /*expected primary-expression before '>' token*/


if(cISBN[i] < 0 || cISBN[i] > 9) {

//etc.

The error message said it all.

gcc will recommend this (parantheses around truth test); it makes code more readable, it makes the issue of this thread clear, and there may be further reasons:

Code:

---

if((cISBN[i] < 0) || (cISBN[i] > 9)) {

---

Thanks alot, here comes another error, help please? :D

input 013190190
output 7 (should be)

But it gave me "ISBN numerical error 10" or "ISBN length error 10" as output instead, I don't know where the 10 came from, try run it...

You have a char array with 10 elements.

You're using gets() to put in 10 char's.

Which leaves the newline still in the keyboard buffer, waiting to much up the next number. Perhaps coincidentally (perhaps not), a line feed char is ascii value 10!

I would add a getchar() after the gets, to pull the newline char off the buffer, and then if your problem is still present.

Your wild indentation makes your code very much a PITA, to follow. Every opening brace, should have a matching closing brace *directly below it* (in the same vertical column).

This is dreadful, frankly:

Code:

---

            }
            }
            }

---

Which leaves the newline still in the keyboard buffer, waiting to much up the next number. Perhaps coincidentally (perhaps not), a line feed char is ascii value 10! I still don't understand that, please explain?

After replacing gets() with getchar(), it says

Line 272 too many arguments to function `int getchar()'
Line 18 at this point in file

Okay, I changed the positions of the closing brackets thingy, so it's much easier to read.

C++ Reference [C++ Reference]

Quote:

---

Originally Posted by Dakaa

Which leaves the newline still in the keyboard buffer, waiting to much up the next number. Perhaps coincidentally (perhaps not), a line feed char is ascii value 10! I still don't understand that, please explain?

---

To make a long story short, stdin input is up to AND INCLUDING the newline character, so if you call on stdin, that's what gets put in the stdin buffer. If you do not read everything that's in there out, the stdin file pointer is set to wherever you left off.

Quote:

---

Originally Posted by Dakaa

Which leaves the newline still in the keyboard buffer, waiting to much up the next number. Perhaps coincidentally (perhaps not), a line feed char is ascii value 10! I still don't understand that, please explain?

replaced gets() with getchar()

Line 272 too many arguments to function `int getchar()'
Line 18 at this point in file

k, i changed the positions of the closing brackets thingy.

---

Good, because I'm not checking code that looks like Bugs Bunny wrote it.

Say you have a gets(); taking a string, into your char array.

The string is 10 char's long, and your char array is also 10 elements long. Note that there is NO ROOM for the newline which is in the keyboard buffer, and generated every time you hit the Enter key.

Say I enter this: 0123456789 - OK, that's 10 digits, and it all fits into the char array[], but what you don't see is this:

0123456789\n - which is what's really there.

So the newline char '\n' is left in the keyboard buffer. The next input will have to deal with it - by ignoring it and skipping over it (like scanf() will do for a number), or accept that newline char, as your intended input, like scanf() will do when it's expecting a char (%c) format.

The newline char is what is written to the file, *BUT* when the file is opened for input as a text file, the OS will change that newline, into *TWO* chars - a line feed (ascii 10), and a Carriage Return(ascii 13).

In binary file mode, that change of the newline, does not occur.

Problems with newlines are probably the most common problem we see on this forum. I don't know if it's your problem, because your code was so MICKY MOUSE, in format, I started cursing at it, and quit.

I'll try and look it through, again.

I adjusted your program to something I could follow, and that compiles:

Code:

---



//#include <iostream.h>  //
#include <conio.h>
#include <stdio.h>
#include <string.h>

int main()
{
  char cISBN[10] = {"013190190"};
  int i,iLen,iNNF,iISBN[9],iTotal,iCheck;
   
/* for(i=0;i<10;i++)
  {
      cISBN[i]='\0';
  }
                 
  printf("Enter ISBN ");
  gets(cISBN);
*/
  iLen=strlen(cISBN);
  if(iLen!=9)
  {
      printf("ISBN length error ");
  }
                               
  else
  {
      iNNF=0;
      for(i=0;i<iLen&&iNNF==0;i++)
      {
        if((cISBN[i] - '0'< 0)||(cISBN[i] - '0'> 9))
        {
            printf("ISBN numerical error ");
            iNNF=1;
        }
        else
        {
            iTotal=0;
            iISBN[i]=cISBN[i]-48;
            iTotal += iISBN[i]*(i+1);
        }
      }
  }
  printf("iTotal: %d", iTotal);
  getch();
  return 0;
}
/*
Error 1 (gone): if(cISBN[i]<0||>9) /*expected primary-expression before '>' token*/
thanks Adak and MK27.

Error 2:
1*(0)+2*(1)+3*(3)+4*(1)+5*(9)+6*(0)+7*(1)+8*(9)+9* (0)=139
139/11=12 rem 7
139=7(mod11)
Check digit is 7.

my horrible code
input 013190190
output 7

it gave me "ISBN numerical error 10" instead of 7, I don't know where the 10 came from
*/

---

The code runs fine, but your math is off. Any number times zero, has a product of zero iirc, not 139.

A million times zero is still just zero. (1,000,000 * 0 == 0)

So re-check your equation, and I'll look back for it, after I eat some overdue dinner.

If I've goofed up your program during the adjustment, let me know.

Code:

---

iTotal=0; /*clear iTotal*/
iISBN[i]=cISBN[i]-48; /*turn ASCII numbers to base 10 for doing the arithmetic part next*/
iTotal+=iISBN[i]*(i+1); /*times the element by 'it's position + 1', since ISBN weighting values are 1,2,3,4,5,6,7,8,9 and initial i is 0, and add it to iTotal*/

iCheck=0; /*clear iCheck*/
iCheck=iTotal%11; /*iCheck becomes the remainder of iTotal divided by 11, ISBN uses mod 11*/
cout<<(iCheck); /*output iCheck, the remainder aka the ISBN check digit, and I used cout because printf gave me errors*/

---

So, what is wrong in my calculations

I don't know. When it says the "weighting values" are 123456789, does that mean the zero's in our ISBN example are wrong?

All I can say is that the right values got into the char array, they were then translated into their numerical value, and went into the calculation loop.

I will ponder the matter. Please check Google for an actual equation.

Example, isbn is 013190190, you times the first isbn digit by 1, second digit by 2, third digit by 3, fourth digit by 5, fifth digit by 5, sixth digit by 6, seventh digit by 7, eighth digit by 8 and last digit by 9, because isbn's weight values are 1,2,3,4,5,6,7,8,9. Then you add 'em up which gives us 139, and isbn uses mod 11, so you divide the total by 11 and the remainder is the check digit.

If the weight values are 9,1,4,6,3,7,5,2,8, you times the first digit by 9 and the second by 1 and third by 4 blah blah blah.

Need to get this code working, before I start my other assignment which is similar to this, 'Australian Tax Number', understanding the concept is easy, but not writing it into c. (for me)

EDIT: Sorry for the bad grammar, English is my 2nd language.

OK, let's see how that works in the program, now.

Back in a bit.

We weren't dividing and using the remainder, nor initializing iTotal in the right place:

Code:

---



//#include <iostream.h>
#include <conio.h>
#include <stdio.h>
#include <string.h>

int main()
{
  char cISBN[10] = {"013190190"};
  int i,iLen,iNNF,iISBN[9],iTotal,iCheck;
   
/* for(i=0;i<10;i++)
  {
      cISBN[i]='\0';
  }
                 
  printf("Enter ISBN ");
  gets(cISBN);
*/
  iLen=strlen(cISBN);
  if(iLen!=9)
  {
      printf("ISBN length error ");
  }
                               
  else
  {
      iTotal = iNNF=0;
      for(i=0;i<iLen&&iNNF==0;i++)
      {
        if((cISBN[i] - '0'< 0)||(cISBN[i] - '0'> 9))
        {
            printf("ISBN numerical error ");
            iNNF=1;
        }
        else
        {
            //iTotal=0;
            iISBN[i]=cISBN[i]-48;
            iTotal += iISBN[i]*(i+1);
        }
      }
  }
  printf("\niTotal: %d  Check digit: %d\n", iTotal, (iTotal % 11));
  getch();
  return 0;
}
/*
Error 1 (gone): if(cISBN[i]<0||>9) /*expected primary-expression before '>' token*/
thanks Adak and MK27.

Error 2:
1*(0)+2*(1)+3*(3)+4*(1)+5*(9)+6*(0)+7*(1)+8*(9)+9* (0)=139
139/11=12 rem 7
139=7(mod11)
Check digit is 7.

my horrible code
input 013190190
output 7

it gave me "ISBN numerical error 10" instead of 7, I don't know where the 10 came from
*/

---

thanks...

You're welcome, Dakaa.

To set a variable to zero, it's = 0.

'0' is the char of 0, and has the value of ascii 48, iirc.

The computer world is your world - do it the way you want to do it. I'd suggest fgets(with stdin as the filename), because it lets you limit the amount of char's going into your buffer.

But you could also get 1 digit as a char, at a time, and use a for loop to control it.

C has a function to check if a char is a number or not. isdigit(), and you'll need ctype.h as an include file.

*sigh*, been doing this all day, error number 2 is killing me.

Code:

---

#include <iostream.h>
#include <conio.h>
#include <stdio.h>
#include <string.h>

int main()

{
    char cISBN[10];
    int i,iLen,iNNF,iISBN[9],iTotal;
   
    for(i=0;i<10;i++)
    {
                    cISBN[i]='\0';
    }
                   
                    printf("Enter ISBN to calculate Check Digit ");
                    gets(cISBN);
                    iLen=strlen(cISBN);
                   
                    if(iLen!=9)
                    {
                                printf("ISBN length error ");
                    }
                               
                                else
                                {
                                    iNNF=0;
                                    for(i=0;i<iLen&&iNNF==0;i++)
                                    {
                                                              if((cISBN[i]<0)||(cISBN[i]>9))
                                                              {
                                                                                  printf("ISBN numerical error ");
                                                                                  iNNF=1;
                                                              }
                                                                                 
                                                                                  else
                                                                                  {
                                                                                      iISBN[i]=cISBN[i]-48;
                                                                                      iTotal+=iISBN[i]*(i+1);
                                                                                  }
                                    }
                                }
                               
                                                                                      printf("%d",(iTotal%11));                   
                                                                                      getch();
                                                                                      return 0;
                                                                                     
}

/*something is wrong in BOLD, the output is either "ISBN numerical error 10" or "ISBN length error 10" and I don't know what the hell the 10 is...*/

---

iNNF is Non-Numerical Flag.

Code:

---

    char cISBN[9];
   
    for(i=0;i<10;i++)
    {
                    cISBN[i]='\0';
    }

---

If you are going to access elements 0..9, then you need to have at least 10 elements in the array - you only have 9.
Further, an old ISBN number (ISBN-10) is 10 digits long. If you want to have a C-style STRING containing a 10 digit "number", then you need an array of 11 chars, since you need 10 characters of the ISBN _and_ the zero to indicate the end of the string.

Also, do not use gets() to read the string in - if someone enters a new-steyle 13-digit ISBN, your program is likely to crash (or at least do strange things). Use fgets() or some other function that has can stop inputting when there is no space to store the string.

--
Mats

cISBN[10], 9 characters of ISBN and 1 empty space, thanks for pointing that out. I'm trying to do it the noob way my teacher taught me, but the output is weird and we are doing the old style ISBN, 9 Digits + 1 Check Digit.

hello.

howdy