The fonts supplied in this package are PCL soft fonts. They are so named to differentiate from hardware fonts. Soft fonts reside in the RAM area instead of the ROM in a printer. Although they can be used as if a built-in hardware font, they can not survive a power outage. Therefore, we recommend that your application sends the font at the begining of every print job to avoid situations that the fonts are lost because someone just pressed the power button. Some high-end printers store soft fonts in their hard drive and automatically load the fonts at the startup. In this case, the soft fonts can be treated as if part of the printer.

For applications to use a soft font, the font must be sent to the printer first. This process is called downloading. The font only needs to be sent once, and will reside in the printer for all the time until a power recycle happens. When your application needs to print the barcode, it sends a special command to switch from the default font to the barcode font. This is called selecting font. After the font is selected, you send the full barcode string (which includes start character, data, checksum and stop character) to printer. At last, you send a PCL command to tell printer to switch back to the default font.

A PCL command always begins with the ESC character (referred as <esc> throughout of this manual). The ASCII value for this character is 27. It is followed by one or two characters (called commands). A PCL command may contain parameters, and termination characters. If you are not familiar with PCL commands, you may want to obtain the [PCL Technical Reference Manual], part number 5021-0377 from HP.