Specifications

On a dot-matrix printer, you might be able to select various resolutions, fonts, and speeds, depending
on the printer’s capabilities. The printer driver you install on your PC is designed to generate the
appropriate escape codes based on the options you specify in your application and your printer driver
configuration. If your printer driver cannot generate the codes you desire, you normally can set a par-
ticular font, size, and enhancement for an entire document through the printer’s control panel or
control software.
Escape codes are not as standardized as PDLs; you might see different printers use different codes for
the same function. Epson, for example, has long been a market leader in the dot-matrix printer indus-
try, and its escape codes have come to be accepted by some other manufacturers. However, the accep-
tance of the codes has not been general enough for them to be called an industry standard.
Epson’s escape code standards are ESC/P for their older dot-matrix printers and ESC/P2 for newer dot-
matrix printers and most inkjet printer models. ESC/P was the original Epson version and didn’t sup-
port built-in scalable fonts. ESC/P2 does support built-in scalable fonts found in Epson’s newer
dot-matrix and inkjet printers and works well with Windows 3.x and 9x/Me.
Host-Based/GDI
An increasing number of low-cost inkjet and laser printers don’t use either “classic” PDL (PostScript or
HP-PCL) but instead use the computer to render the page for printing. These printers are called host-
based printers. Some variations on host-based printing include printers that use the Windows GDI
(graphics device interface) engine to image the page (GDI printers) and Hewlett-Packard’s line of
Printing Performance Architecture (PPA) printers. In theory, these printers have some advantages:
■ Low cost. Because the computer has already rendered the page, the printer doesn’t need to
include a PDL, reducing the printer price.
■ Faster computer means faster printing. Because most of the printing work is being done by the
host computer, speeding up the computer by adding RAM, increasing processor speed, or using
IEEE-1284 bidirectional printer connections (EPP/ECP ports and cables) can improve printing
speed. In 1996 tests by PC Magazine, the improvements ranged from a modest 5% to 87%, with
complex images showing a bigger improvement than simple text-only print jobs.
■ Flexible architecture with PPA. Hewlett-Packard’s PPA, depending on the printer, might have virtu-
ally all printer functions performed in the computer (for economy) or might move some fea-
tures into the printer (for performance).
Although host-based printing has its advantages, it also has several key disadvantages:
■ No direct connection equals no printing. Host-based printers must be tied directly to the host for
printing because all they do is produce the finished image. This “gotcha” becomes apparent
when your new SOHO or departmental network can’t print because the printers no longer have
a true host to work with. This affects both GDI-based printers and HP’s PPA product line. The
need for a host prevents these printers from working with network print servers, such as HP’s
JetDirect series. This also can be an issue with sharing a printer via peer networking.
■ Problems with printing from non-Windows applications. Depending on how the host-based printer
is designed, it might not be capable of printing from any operating system other than
Windows. Some printers can print from a “DOS box”—an MS-DOS session that runs within
Windows. The issue of support for increasingly popular operating systems, such as Linux, could
also be a big problem for some users.
■ Lower performance levels. Many vendors of host-based printers built these printers for casual
users. Although the print resolutions of a host-based printer might equal that of a printer with a
true PDL, print speeds are often slower.