>My customer wants to include barcode feature into my VFP application. Do I need to purchase some barcode fonts or barcode libraries to do it. If yes, which do you recommend?
Does the customer's app need to produce barcoded output? If so, the choice of what tool to use will depend on wht tool the printer output is created with - something that uses the Report Writer can benefit directly in many cases by using a barcode font in the report (it has to be installed on each system using it.) Other output mechanisms will require use of a specialized barcode add-on, and if you need to integrate dedicated barcode printing devices, you are very likely to have to shift how you create the output for the barcode printer.
Does the customer's app need to read barcodes? If so, and data entry takes place at or near the keyboard, no change in your code needs to be made - addition of a wedge-style barcode want or gun will read a barcode as if the data were typed into the current control - it behaves exactly as a keyboarded sequence. In many cases, the format of a barcode may not match the standard human inputs/keys used by your application now, so you are likely to have a need to check data entry fields to see if the barcode reader was fired and reformt the data, or check the range and type of input to ensure the barcode reader wan't fired in the wrong place.
If data isn't being collected at the keyboard, you'll have some sort of data collector with a barcode reader on it - there are a wide variety of these devices; most accumulated data and spit it out via a serial port on request, more expensive options may use a continuous wireless LAN connection of some sort. In almost all cases the data collector will be programmable to some extent, but it's virtually certain that the data collector won't use VFP (various flavors of Basic, especially VB for CE with newer Windows CE devices, are most common.)
Lots of things to be aware of - cost and output quality are two major factors. Dedicated barcode readers/printers/software is not cheap, and you tend to get exactly what you pay for - the low-end stuff won't stand up well to continuous use. Output devices get very expensive very quickly - we paid over $1800 for the low-end barcode printer on our site, and the high-end (and significantly faster) printer ran to nearly $5000.
Output quality - you will not get reliable barcoded output off a dot matrix printer. Period. Laser printer output is normally high enough quality, and the dedicated barcode printers use either a single pass film ribbon or thermal printing.
You will not get reliable barcode output on poor quality stock. Paper that smudges, swells or shrinks because of variations in humidity, does not offer a consistent reflectivity, or does not consistently align will result in unusable/unreadable barcodes. Quality output stock is a necessity, and again, it is not cheap.
If you're going to send output documents outside of your own environment, there are several different barcode standards - coordinate which one the recipient expects before you start. Many barcoded output recipients have very strict rules that must be adhered to and verified for compliance in advance of the recipient accepting the barcoded output. Shipping companies like UPS and FedEx are really picky abouyt compliance testing.
To summarize, it isn't cheap to do right, and its worthless if done wrong - 95% ACCURACY MEANS THAT 1 IN 20 READS WILL FAIL IN SOME FASHION. Sometimes an error will not be detectable unless you've done something like added check digits to verify the value returned was in proper format and cleanly read.
Other than these things, barcode adaptation is easy...
