The printer driver receives GDI calls and translates them into a stream of printer commands.
A printer driver has a certain number of functions that must be supported in order to function properly.
Most printer drivers use one of 3 built-in windows drivers called Unidrv, PScript, and PCL.
These built-in drivers act as a framework to support most of the basic functionality of the 3 most common types of printers, dot matrix, Postscript, and PCL (Printer Control Language).
By using these built-in drivers, printer manufacturers can spend less time "reinventing the wheel" and more time providing additional features in the products.
It also provides the benefit of having a team of software engineers working to provide updates to core functionality.
There are some printer drivers on the market that produce image data, such as bitmap, tiff, or jpeg images of the printed page.
In some cases, image formats are sufficient for their intended purpose, but it doesn't make a very good archive format for several reasons:
- The image is rendered at a fixed resolution. If the resolution is too high, it takes up more disk space. If the resolution is too low, it becomes grainy and possibly illegible.
- The contents of images cannot be textually searched. Once the text of a print job is rasterized, it requires Optical Character Reader (OCR) software to convert the image back to text, which is a slow process.
- Reprinting an image representation of an entire page requires sending every pixel of the image including blank areas of the page, increasing the print file size.
- Even though image data is usually compressed on disk, it needs to be decompressed when loaded into memory, increasing minimum system requirements.
A better choice of file format for archival purposes is Portable Document Format, or PDF. PDF is a subset of the Postscript printer language, and is an open standard.
As a matter of fact, a Postscript file can easily be converted to PDF using free tools, such as Ghostscript, or commerial tools, such as Adobe Acrobat Distiller.
For this purpose, a printer driver that produces Postscript is required, such as the Alphatronics PS Driver.
There are also many Postscript printer drivers that ship with Windows, so there is no need to purchase a third party driver.