Scanning barcodes

Hi All!

I want to know more about barcoding and how to write "barcoding software", what I mean is how to interface with a scanner and even how to manualy check if the program is getting correct data, and interpretting it correctly. How do I convert those lines to numbers? How do I go about interfacing with the scanner (handheld connected to PC). And which software is best to use to create and later manipulate the database of stock items which I want to scan in. MS Acces maybe? I expect about 2-3000 items of stock. I know there are more than one barcode standard. A UK and an International one (I think).

If anybody has done anything like this, please drop me a line.

Thanks for your time/help/advise.

Cheers
Rossi.


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Allen Van Der Ross
Systems Programmer
Software Performance Improvement
South Africa
E-Mail: [email protected]
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Consider using OPOS (OLE for Point-Of-Sale) drivers. Check out the home page at
http://www.microsoft.com/industry/re.../opos/home.stm

Bar code scanners usually are capable of understanding many barcode symbologies. The ones they do understand at any time are the ones the user has configured them to understand. There are a dozen or so common symbologies. Code 39 is the most common. But most scanners can also read grocery store UPC labels, etc.

And 2D barcodes like UPS uses are getting more common. PDF417 is the most common. From a programming viewpoint, they are just the same as 1D barcodes. The scanner does all the work. It takes a special scanner to read a 2D code, and you may get 1K of data, but the data is ASCII.

Many barcodes have a check digit or other redundancy. The scanner reads the code and checks the check digit. If it does not agree, the scanner gives no data. Some scanners are capable of reconstructing a damaged barcode. Your program knows nothing of this. It either gets good data or no data.

Scanners typically do the decoding internally. There are two common types. One connects to your serial port. You read it like any serial device. Your program gets ASCII data and stores it in a variable.

The other goes between your keyboard and computer. When you type, the data goes through the scanner unchanged. Likewise data that goes back to the keyboard (to light the caps lock key, for example). When you scan a bar code with this kind of scanner, the computer thinks the data came from the keyboard. After all, that is where the scanner is connected. So no special programming is needed.

Some programs print barcodes. This is best done with special purpose barcode printers. Dot matrix printers don't have the resolution. Laserjets can print OK barcodes.

But most of the time, people want it printed on special stock, like labels with sticky backs. They may want high speed printers. They may want special inks that last for years, or really cheap paper so they can print them by the thousands.

Most barcode printers requires special commands
to print. The command may tell it not just what a barcode says, but where and how big and what symbology, etc. Text is the same. A command is required.