User Guide

LaserWriter background
Downloading
Downloading is the means by which the font description is
sent from the computer to the PostScript printer.
PostScript printers contain powerful computers which
allow them to accept a variety of fonts and graphics
commands expressed in PostScript. In particular, they can
accept new typefaces through the process of downloading.
PostScript printers have two important types of built-in
memory. The first is ROM (Read-Only Memory) which is
unchangeable. ROM holds its information indefinitely,
even when the power is turned off. The basic printer
control program and several typefaces are programmed
into the ROM and thus are not changeable. The second
type of built-in memory is RAM (Random-Access
Memory) which can be changed. However, RAM loses its
contents each time the power is turned off. Downloaded
fonts are put into RAM, as is the image of the page to be
printed. RAM has enough space to hold three to five fonts,
depending on their complexity.
Both outline fonts and bitmap fonts may be downloaded
into RAM, so your computer is able to print documents
using bitmap fonts when the outline font is unavailable.
However, the process is very slow, due to the way bitmap
fonts are used. Downloaded fonts can further be divided
into two classes: permanent and transient.
Permanent fonts
Permanent is a misnomer here, since the permanent fonts
are only semi-permanent. Unless you have a hard disk
attached to your printer, permanent fonts are downloaded
once, and remain available until the LaserWriter is turned
off. If your printer does have a hard disk attached, you
can download your fonts permanently to the hard disk.
Permanent fonts are good for those installations which do
a considerable amount of processing, using just a few
frequently used fonts, and don’t want to incur the
overhead of downloading them with each printed document.
Transient fonts
Fontographer User's Manual
C: General information Page #9