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Barcode check digits

Learn how to check digits of barcodes in Amlib.

Check digits

Amlib allows variations in the validation of Stockitem and Borrower numbers (Item No field in the Stockitem screen and the BarCode field in the Borrower Details screen).

These are mathematically manipulated to give a check digit defined in the Check-digits Calculations table. If the digit (or character) on the card or book being wanded corresponds to a calculation in the table, the article has a valid check digit.

 Note: As there can be more than one entry for Check Digits for Borrowers and Items, the system can handle different types of Barcodes for transactions.

 Caution: Do not change any existing barcode validations unless you are aware of the implications!

Enter a new check digit

  1. Launch the Amlib client
  2. Go to Main > Supervisor > CheckDigits – the Check-digits Calculations screen will display:
  3. Click the F1 New or F2 Insert button – an entry will appear in the table
  4. Complete the entry using the details in the following table:
    heading explanation

    (I) Item (B) Borrower

    Defines whether the calculation is to be set for Item No (Stockitem) or BarCode (Borrower)

    Weights left to right comma separated text

    The multiplication pattern used in the calculation of the barcode check digit. This is usually unique to the barcode supplier

    Use as Cd Depending on remainder

    Depending on the remainder calculated in the barcode algorithm, this table indicates the symbol required for the check digit. In most cases this is a number but could also be a letter. The number of characters indicate the number of characters in the modulo column

    Leading Chars

    Can be specific alpha-numeric characters or any, indicated by #(numeric), ?(alpha) or & (alpha or numeric) the number of characters as typed in the column

    Trailing Chars

    Can be specific alpha numeric characters or any, indicated by #(numeric), ?(alpha) or & (alpha or numeric) the number of characters as typed in the column


    The number of characters in the barcode including the check digit

    Mod (Modulo)

    The number of characters in the modulo (calculation)


     Note: It may be necessary to widen the columns to add more digits to the barcode number. At the column header place the cursor on the column line. A symbol of a double arrow will display which can be dragged with the left mouse button to make the column large enough to fit the required characters

  5. Click the F3 Save button when complete – a prompt will display with the following message: A new OFFLINE.INI file has been created for use with Offline Issues, Offline Returns and Offline Stocktake. 
  6. Click the OK button.


After setting the parameters, it is possible to wand the item in the barcode in the box at the top of the screen, indicate the type of barcode (Item or Borrower) and test it using the F6 Test button. A prompt will display indicating whether it was a valid or an invalid barcode.