I am working on a project where we have to provide pseudocode as part of the problem solving strategy

Question

I am a 2nd year student and I am working on a Technical Programming project where we are asked to solve a problem about ISBNs. I am now at a step where I have to verify with someone else that my pseudocode works, hence I joined the forum. Basically here I am validating that an ISBN is correct. This is how I made my pseudocode using knowledge from other sites as well. To give some background knowledge, an ISBN is divided into 4 parts seperated by a hyphen: group code, publisher's code, number of the book title and the check digit. example of a 10 digit ISBN: 0-14-012499-3. You can use this or any ISBN of a text book you have to validate my pseudocode

Display 'Enter a 10 character ISBN'
GET ISBN
total = 0;
FOR counter GOES FROM 1 TO 9//represents the 9 characters excluding the check digit
thisDigit = character 'counter' of 'ISBN';//each character of the ISBN
total = total + thisDigit;//checks the 9 characters of ISBN
END FOR
checkDigit = 10th character of ISBN;
remainder = 11-(total / 11);// this is the formular to calculate the check digit
calculatedCheckDigit = 11 - remainder;
IF(calculatedCheckDigit = 10)
calculatedCheckDigit = 'X';
END IF
IF(calculatedCheckDigit = checkDigit)
Display('ISBN is valid')

Thank you

Sam Hobbs · Answer

Using 0735615799: Pasting 0+7+3+5+6+1+5+7+9 into the Windows Calculator gives 43. Divide that by 11 gives 3.9090909090909090909090909090909. Are we supposed to round that off so it becomes 4 or simply truncate so it becomes 3? 11 - 4 = 7 11 - 7 = 4 4 != 9 The ISBN is valid but either I did not follow the pseudocode properly or the pseudocode is invalid. Did you try the pseudocode yourself before posting here? If you can show your iintermediate results as I did then that will help.

Avuya Mxoli · Answer

thanks for that input this is how I did it 0+1+4+0+1+2+4+9+9 = 30 then remainder = 11 - (30/11) we then calculate the brackets which gives us 2.727... then 11-2.727.. = 8.2727.. then round that to 8 and the next step is 11- remainder; 11-8 = 3.

Avuya Mxoli · Answer

Thanks a lot you round off your answer I'll correct that in my pseudocode

Vulpes · Answer

I don't think that the pseudo-code for the check digit is quite right. Using the number you gave as an example: remainder = 11 - (30/11); // which using integer arithmetic is 9 calculatedCheckDigit = 11 - 9; // which is 2 but the answer should be 3 I'd express it instead as: remainder = total modulo 11; // which is 8 when total = 30 Apart from that it looks OK to me.