ORIGIN OF BAR CODE:-
A Barcode system must have a source of Barcodes and a way to read them. Barcode labels fall into one of the following categories: PREPRINTED or PRINTED-ON-DEMAND.

PREPRINTED BAR CODES:-
Using preprinted labels is the most economical way to get high-quality Barcodes. This places some restrictions on you, because the information in the bar codes must be determined in advance. In many cases this is acceptable but in some it is not. Preprinted Barcodes are used where very durable, high-quality labels are necessary to withstand the environment (such as on printed circuit boards), or where high-volume packaging or labeling is done.

Examples of preprinted Barcodes are :
• Bar Codes on Packaging:- The most common example of preprinted bar codes are those you see on packaging for retail sale. Grocery stores are the most common application, but the system is gradually working its way up the manufacturing chain.
• Stickers or Tags:- In many cases, you need to identify a particular item as unique. There are several companies that will print stickers, pallet tags, item tags, or other types of very high quality bar code labels in any required sequence.

Either of these systems works very well when you can manage the assignment of codes beforehand.

In many cases, you can also use assigned codes by generating a correlation between the bar code and another significant value
For example, you could use a randomly numbered sticker or tag and have the user type in the corresponding invoice number, control number, or other information that goes with it.

INTERFACING A BARCODE READER TO A PC:-
All application programs support bar code reading as long as you have the right equipment. Bar code readers are available with two types of output - either "keyboard wedge" output or "RS232" output

KEYBOARD WEDGE:
The bar code readers with keyboard wedge output plug directly into the keyboard port on your PC and they also provide a pigtail connector so that you can plug in your keyboard at the same time. When you scan a bar code with the keyboard wedge bar code reader, the data goes into the computer just as if it were typed in on the keyboard. This makes it extremely easy to interface the bar code reader to any application that is written to accept keyboard data.

The keyboard wedge interface is extremely simple however it has a few drawbacks. If you swipe a bar code, the cursor has to be in the correct input field in the correct application otherwise you end up reading bar code data into whatever application has the focus. This can cause all sorts of potential problems as you can imagine. The keyboard output also is limited in that you cannot modify the data in any way before sending it into the program that is to receive the data.

For example, if you needed to parse a bar code message into multiple pieces or remove some of a bar code message or add in a date or time stamp you would not be able to with a normal keyboard wedge reader.

RS232 OR SERIAL INTERFACE:
The other possible output option is to get a bar code reader with an RS232 or "Serial" interface. With these types of bar code readers, you connect the reader to an available serial port on the back of your PC. You would then need a program called a "Software Wedge" to take the data from the bar code reader and feed it to the application where you want the data to go. The disadvantage to this approach is that it is a little more complex however you gain much more control over how and where your data ends up when you read a bar code.

Our WinWedge product line is designed just for this purpose. WinWedge is an executable program that can pass serial data back and forth to other programs using either DDE (Dynamic Data Exchange) or by converting incoming serial data to keystrokes (i.e. it stuffs the keyboard buffer with the incoming serial data). With WinWedge, you can control exactly where the data goes in the target application and you can also perform all sorts of modifications on the data before it is sent to the application including parsing or translating the data as well as adding additional keystrokes or date and time stamps to the data.

WinWedge is extremely easy to use and is designed to have you up and running sending and receiving serial data directly from within your application in just a few minutes. Because WinWedge can pass data using DDE, you can set your application up to insure that the bar code data always goes where it is supposed to go and you can also have your application running in the background and still accept bar code input while you run some other program in the foreground. WinWedge is without question the most robust way to interface a bar code reader to a PC with the least amount of effort.

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