The Barcode Mask Character table contains the possible characters used for barcode masks.
Barcode mask characters are alphabetical letters that are replaced with numbers when the program generates
the barcode from the input typed in.
Barcode mask characters are used for several types of barcode generating, for example for item, customer, and employee barcodes.
If an item, identified by a barcode, has a barcode mask, the program checks each digit of the barcode typed in against the corresponding barcode mask digit
and generates missing digits according to the mask.
For retail items, the program generates barcodes from the Barcode No. field in the Barcode table,
for the relevant barcode entries.