PRINTERS
Printers are electro-mechanical output devices that are used
to put information from the computer
onto paper. They have been around since the introduction of
the computer. Other than the display
monitor, the printer is the most popular peripheral
purchased for a computer, because most people
need to have paper copies of the documents they create.
There are three major type of printer:-
• Impact printers
• Bubble-jet printers
• Laser printers (page printers)
Impact Printers
There are several categories of printers, but the most basic
type is the category of printers known as
impact printers. Impact printers, as their name suggests,
use some form of impact and an inked
ribbon to make an imprint on the paper. They use an inked
ribbon and an impact head to make
letters on the paper. There are two major types of impact
printers: daisy wheel and dot matrix.
Daisy-Wheel Printers
These printers contain a wheel (called the daisy wheel
because it looks like a daisy) with raised
letters and symbols on each “petal”. When the printer needs
to print a character, it sends a signal to
the mechanism that contains the wheel. This mechanism is
called the printhead. The printhead
rotates the daisy wheel until the required character is in
place. An electromechanical hammer
(called a solenoid) then strikes the back of the “petal”
containing the character. The character
pushes up against an inked ribbon that ultimately strikes
the paper, making the impression of the
requested character.
Their speed is rated by the number of characters per second
(cps) they can print. The early printers
could only print between 2 and 4 characters per second.
The main disadvantage to this type of printer is that it
makes a lot of noise when printing
The daisy-wheel printer has a few advantages, of course.
First, because it is an impact printer, you
can print on multipart forms (like carbonless receipts),
assuming they can be fed into the printer
properly. Second, it is relatively inexpensive compared to
the price of a laser printer of the same
vintage. Finally, the print quality is comparable to a
typewriter because it uses a very similar
technology. This typewriter level of quality was given a
name: letter quality (LQ).
Dot-Matrix Printers
These printers work in a manner similar to daisy-wheel
printers, except that instead of a spinning,
character-imprinted wheel, the printhead contains a row of
“pins” (short sturdy stalks of hard wire).
These pins are triggered in patterns that form letters and
numbers as the printhead moves across the
paper.
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The pins in the printhead are wrapped with coils of wire to
create a solenoid. Also, the pins are held
in the rest position by a combination of a small magnet and
a spring. To trigger a particular pin, the
printer controller sends a signal to the printhead, which
energizes the wires around the appropriate
print wire. This turns the print wire into an electromagnet,
which repels the print pin, forcing it
against the ink ribbon and making a dot on the paper. It’s
the arrangement of the dots in columns
and rows that creates the letters and numbers we see on the
page.
The main disadvantage to dot-matrix printers is their image
quality, which can be quite poor
compared to the quality produced with a daisy wheel.
Dot-matrix printers use patterns of dots to
make letters and images, and the early dot-matrix printers
used only 9 pins to make those patterns.
The output quality of such printers is referred to as “draft
quality”—good mainly for providing
your initial text to a correspondent or revisor. Each letter
looked “fuzzy” because the dots were
spaced as far as they could be spaced and still be perceived
as a letter or image. As more pins were
crammed into the printhead (17-pin and 24-pin models were
eventually developed), the quality
increased because the dots were closer together. Dot-matrix
technology ultimately improved to the
point where a letter printed on a dot-matrix printer was
almost indistinguishable from typewriter
output. This level of quality is known as near letter
quality (NLQ).
Dot-matrix printers are still noisy, but the print wires and
printhead are covered by a plastic dust
cover, making them quieter than daisy-wheel printers. Also,
dot-matrix printers use a more efficient
printing technology, so the print speed is faster (typically
in the range of 36 to 72cps). Some dotmatrix printers (like the Epson DFV
series) can print at close to a page per second! Finally, because
dot-matrix printers are also impact printers, they can also
use multipart forms. Because of these
advantages, dot-matrix printers quickly made daisywheel
printers obsolete.
Bubble-Jet Printers
The next category of printer technology is one of the most
popular in use today. This category of
printers is actually an advanced form of an older technology
known as ink-jet printers. Both types
of printers spray ink on the page, but ink-jet printers use
a reservoir of ink, a pump, and an ink
nozzle to accomplish this. They were messy, noisy, and
inefficient. Bubble-jet printers work much
more efficiently. Bubble-jet printers are very basic
printers. There are very few moving parts.
Every bubble-jet printer works in a similar fashion. First
of all, every bubble-jet printer contains a
special part called an ink cartridge. This part contains the
printhead and ink supply, and it must be
replaced as the ink supply runs out. A typical ink cartridge
(size: approximately 3 inches by
11/2 inches). Inside this ink cartridge are several small
chambers. At the top of each chamber is a
metal plate and tube leading to the ink supply. At the
bottom of each chamber is a small pinhole.
These pinholes are used to spray ink on the page to form
characters and images as patterns of dots
(similar to the way a dot-matrix printer works, but with
much higher resolution).
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How Printers Work
When a particular chamber needs to spray ink, an electric
signal is sent to the heating element,
energizing it. The elements heat up quickly, causing the ink
to vaporize. Because of the expanding
ink vapour, the ink is pushed out the pinhole and forms a
bubble of ink. As the vapour expands, the
bubble eventually gets large enough to break off into a
droplet. The rest of the ink is pulled back
into the chamber by the surface tension of the ink. When
another drop needs to be sprayed, the
process begins again.
When the printer is done printing, the printhead moves back
to its maintenance station. The
maintenance station contains a small suction pump and ink
absorbing pad. To keep the ink flowing
freely, before each print cycle, the maintenance station
pulls ink through the ink nozzles using
vacuum suction. This expelled ink is absorbed by the pad in
the maintenance station. The stations
serve two functions: to provide a place for the printhead to
rest when the printer isn’t printing, and
to keep the printhead in working order.
Laser Printers (Page Printers)
Laser printers are referred to as page printers because they
receive their print job instructions one
page at a time (rather than receiving instructions one line
at a time). There are two major types of
page printers: those that use the Electrophotographic (EP)
print process and those that use the lightemitting diode (LED) print process.
Each works in basically the same way, with slight differences.
Electrophotographic (EP) Laser Printer Operation
When Xerox and Canon developed the first laser printers in
the late 1980s, they were designed
around the Electrophotographic (EP) process (a technology
developed by scientists at Xerox). This
technology uses a combination of static electric charges,
laser light, and a black powdery substance
called toner. Printers that use this technology are called
EP process laser printers, or just laser
printers. Every laser printer technology has its foundations
in the EP printer process. Let’s discuss
the basic components of the EP laser printer and how they
operate so you can understand the way
an EP laser printer works.
Basic Components
Any printer that uses the EP process contains eight standard
assemblies. These assemblies are the
toner cartridge, fusing assembly, laser scanner,
high-voltage power supply, DC power supply,
paper transport assembly (including paper pickup rollers and
paper registration rollers), corona, and
printer controller circuitry.
The Toner Cartridge
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The EP toner cartridge, as its name suggests, holds the
toner. Toner is a black, carbon substance
mixed with polyester resins (to make it “flow” better) and
iron oxide particles (to make the toner
sensitive to electrical charges).
These two components make the toner capable of being
attracted to the photosensitive drum and
capable of melting into the paper. In addition to these
components, toner contains a medium called
the developer (also called the carrier), which “carries” the
toner until it is used by the EP process.
The toner cartridge also contains the EP print drum. This
drum is coated with a photosensitive
material that can hold a static charge when not exposed to
light (but cannot hold a charge when it is
exposed to light—a curious phenomenon, and one that EP
printers exploit for the purpose of
making images). Finally, the drum contains a cleaning blade
that continuously scrapes the “used”
toner off the photosensitive drum to keep it clean.
An EP toner cartridge
In most laser printers, “toner cartridge” means an EP toner
cartridge that contains toner
and a photosensitive drum in one plastic case. In some laser
printers, however, the toner
and photosensitive drum can be replaced separately instead
of as a single unit. If you ask
for a “toner cartridge” for one of these printers, all you
will receive is a cylinder full of toner.
Consult the printer’s manual to find out which kind of toner
cartridge your laser printer
uses.
The Laser Scanning Assembly
As we mentioned earlier, the EP photosensitive drum can hold
a charge if it’s not exposed to light.
It is dark inside an EP printer, except when the laser
scanning assembly shines on particular areas
of the photosensitive drum. When it does that, the drum
discharges, but only in that area. As the
drum rotates, the laser scanning assembly scans the laser
across the photosensitive drum.
The EP laser scanning assembly (side view and simplified top
view) Laser light is damaging
to human eyes. Therefore, it is kept in an enclosure and
will operate only when the laser printer’s
cover is closed.
High-Voltage Power Supply (HVPS)
The EP process requires high-voltage electricity. The
high-voltage power supply (HVPS) provides
the high voltages that are used during the EP process. This
component converts house AC current
(120 volts, 60 Hertz) into higher voltages that the printer
can use. This high voltage is used to
energize both the corona wire and transfer corona wire.
DC Power Supply (DCPS)
The high voltages used in the EP process can’t power the
other components in the printer (the logic
circuitry and motors). These components require low
voltages, between +5 and +24Vdc. The DC
power supply (DCPS) converts house current into three
voltages: +5Vdc and –5Vdc for the logic
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circuitry and +24Vdc for the paper transport motors. This
component also runs the fan that cools
the internal components of the printer.
Paper Transport Assembly
The paper transport assembly is responsible for moving the
paper through the printer. It consists of
a motor and several rubberized rollers that each performs a
different function. The first type of
roller found in most laser printers is the feed roller, or
paper pickup roller. This D-shaped roller,
when activated, rotates against the paper and pushes one
sheet into the printer. This roller works in
conjunction with a special rubber pad to prevent more than
one sheet from being fed into the printer
at a time.
Paper transport rollers
Another type of roller that is used in the printer is the
registration roller. There are actually two
registration rollers, which work together. These rollers
synchronize the paper movement with the
image formation process in the EP cartridge. The rollers
don’t feed the paper past the EP cartridge
until the cartridge is ready for it.
Both of these rollers are operated with a special electric
motor known as an electronic stepper
motor. This type of motor can accurately move in very small
increments. It powers all of the paper
transport rollers as well as the fuser rollers.
The Transfer Corona Assembly
When the laser writes the images on the photosensitive drum,
the toner then sticks to the exposed
areas; we’ll cover this in the next section,
“Electrophotographic (EP) Print Process.” How do you
get the toner from the photosensitive drum onto the paper?
Well, the transfer corona assembly is
charged with a high-voltage electrical charge. This assembly
charges the paper, which pulls the
toner from the photosensitive drum.
Included in the corona assembly is a static-charge
eliminator strip that drains away the charge
imparted to the paper by the corona. If you didn’t drain
away the charge, the paper would stick to
the EP cartridge and jam the printer.
There are two types of corona assemblies, those that contain
a corona wire and those that contain a
corona roller. The corona wire is a small diameter wire that
is charged by the high-voltage power
supply. The wire is located in a special notch in the
“floor” of the laser printer (underneath the EP
print cartridge). The corona roller performs the same
function as the corona wire, except that it’s a
roller rather than a wire. Because the corona roller is
directly in contact with the paper, it supports
higher speeds. It is for this reason that the corona wire
isn’t used in laser printers much any more.
Fusing Assembly
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The toner in the EP toner cartridge will stick to just about
anything, including paper. This is true
because the toner has a negative static charge and most
objects have a net positive charge.
However, these toner particles can be removed by brushing
any object across the page. This could
be a problem if you want the images and letters to stay on
the paper permanently!
To solve this problem, EP laser printers incorporate a
device known as a fuser, which uses two
rollers that apply pressure and heat to fuse the plastic
toner particles to the paper. You may have
noticed that pages from either a laser printer or a copier
(which uses a similar device) come out
warm. This is because of the fuser.
The fuser is made up of three main parts: a halogen heating
lamp, Teflon coated aluminium fusing
roller, and a rubberized pressure roller. The fuser uses the
halogen lamp to heat the fusing roller to
between 165 degrees C and 180 degrees C. As the paper passes
between the two rollers, the
pressure roller pushes the paper against the fusing roller,
which melts the toner into the paper.
Printer Controller Circuitry
The final component in the laser printer we need to discuss
is the printer controller assembly. This
large circuit board converts signals from the computer into
signals for the various assemblies in the
laser printer, using the process known as rasterizing. This
circuit board is usually mounted
underneath the printer. The board has connectors for each of
the types of interfaces and cables to
each assembly. When a computer prints to a laser printer, it
sends a signal through a cable to the
printer controller assembly. The controller assembly formats
the information into a page’s worth of
line-by-line commands for the laser scanner. The controller
sends commands to each of the
components telling them to “wake up” and start the EP print
process.
Ozone Filter
Your laser printer uses various high-voltage biases inside
the case. As anyone who has been outside
during a lightning storm can tell you, high voltages create
ozone. Ozone is a chemically reactive
gas that is created by the high-voltage coronas (charging
and transfer) inside the printer. Because
ozone is chemically reactive and can severely reduce the
life of laser printer components, most
laser printers contain a filter to remove ozone gas from
inside the printer as it is produced. This
filter must be removed and cleaned with compressed air
periodically (usually whenever the toner
cartridge is replaced is sufficient).
Electrophotographic (EP) Print Process
The EP print process is the process by which an EP laser
printer forms images on paper. It consists
of six major steps, each for a specific goal. Although many
different manufacturers call these steps
different things or place them in a different order, the
basic process is still the same. Here are the
steps in the proper order:
1. Cleaning
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2. Conditioning
3. Writing
4. Developing
5. Transferring
6. Fusing
Before any of these steps can begin, however, the controller
must sense that the printer is ready to
start printing (toner cartridge installed, fuser warmed to
temperature, and all covers are in place).
Printing cannot take place until the printer is in its
“ready” state, usually indicated by an
illuminated Ready LED light or a display that says something
like “00 READY” (on HP printers).
Step 1: Cleaning
In the first part of the laser print process, a rubber blade
inside the EP cartridge scrapes any toner
left on the drum into a used toner receptacle inside the EP
cartridge, and a fluorescent lamp
discharges any remaining charge on the photosensitive drum
(remember that the drum, being
photosensitive, loses its charge when exposed to light).
This step is called the cleaning step. The EP
cartridge is constantly cleaning the drum. It may take more
than one rotation of the photosensitive
drum to make an image on the paper. The cleaning step keeps
the drum “fresh” for each use. If you
didn’t clean the drum, you would see “ghosts” of previous
pages printed along with your image.
The actual amount of toner removed in the cleaning process
is quite small. The cartridge
will run out of toner before the used toner receptacle fills
up.
Step 2: Conditioning
The next step in the EP process is the conditioning step. In
this step, a special wire (called a
charging corona) within the EP toner cartridge (above the
photosensitive drum) gets a high voltage
from the HVPS. It uses this high voltage to apply a strong,
uniform negative charge (around –
600Vdc) to the surface of the photosensitive drum.
Step 3: Writing
The next step in the EP process is the writing step. In this
step, the laser is turned on and “scans”
the drum from side to side, flashing on and off according to
the bits of information the printer
controller sends it as it communicates the individual bits
of the image. The areas where the laser
“touches” severely reduce the photosensitive drum’s charge
from –600Vdc to a slight negative
charge (around – 100Vdc). As the drum rotates, a pattern of
exposed areas is formed, representing
the images to be printed.
At this point, the controller sends a signal to the pickup
roller to feed a piece of paper into the
printer, where it stops at the registration rollers.
Step 4: Developing
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Now that the surface of the drum holds an electrical
representation of the image being printed, its
discrete electrical charges need to be converted into
something that can be transferred to a piece of
paper. The EP process step that accomplishes this is the
developing step. In this step, toner is
transferred to the areas that were exposed in the writing
step.
There is a metallic roller called the developing roller
inside an EP cartridge that acquires a –
600Vdc charge (called a bias voltage) from the HVPS. The
toner sticks to this roller because there
is a magnet located inside the roller and because of the
electrostatic charges between the toner and
the developing roller. While the developing roller rotates
toward the photosensitive drum, the toner
acquires the charge of the roller (–600Vdc). When the toner
comes between the developing roller
and the photosensitive drum, the toner is attracted to the
areas that have been exposed by the laser
(because these areas have a lesser charge, of –100Vdc). The
toner also is repelled from the
unexposed areas (because they are at the same –600Vdc charge
and like charges repel). This toner
transfer creates a “fog” of toner between the EP drum and
the developing roller.
The photosensitive drum now has toner stuck to it where the
laser has written. The photosensitive
drum continues to rotate until the developed image is ready
to be transferred to paper in the next
step, the transferring step.
Step 5: Transferring
At this point in the EP process, the developed image is
rotating into position. The controller notifies
the registration rollers that the paper should be fed
through. The registration rollers move the paper
underneath the photosensitive drum, and the process of
transferring the image can begin, with the
transferring step. The controller sends a signal to the
corona wire or corona roller (depending on
which one the printer has) and tells it to turn on. The
corona wire/roller then acquires a strong
positive charge (+600Vdc) and applies that charge to the
paper. The paper, thus charged, pulls the
toner from the photosensitive drum at the line of “contact”
between the roller and the paper because
the paper and toner have opposite charges. Once the
registration rollers move the paper past the
corona wire, the static-eliminator strip removes all charge
from that “line” of the paper. If the strip
didn’t bleed this charge away, the paper would attract
itself to the toner cartridge and cause a paper
jam.
The toner is now held in place by weak, electrostatic
charges and gravity. It will not stay there,
however, unless it is made permanent, which is the reason
for the next step, the fusing step.
Step 6: Fusing
In the final step, the fusing step, the toner image is made
permanent. The registration rollers push
the paper toward the fuser rollers. Once the fuser grabs the
paper, the registration rollers push for
only a short time more. The fuser is now in control of
moving the paper.
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As the paper passes through the fuser, the 350-degree F
fuser roller melts the polyester resin of the
toner and the rubberized pressure roller presses it
permanently into the paper. The paper continues
on through the fuser and eventually exits the printer.
Once the paper completely exits the fuser, it trips a sensor
that tells the printer to finish the EP
process with the next step, the cleaning step. At this
point, the printer can print another page and
the EP process can begin again.
Summary of the EP Print Process
First, the printer uses a rubber scraper to clean the
photosensitive drum. Then the printer places a
uniform, negative, –600Vdc charge on the photosensitive drum
by means of a charging corona. The
laser “paints” an image onto the photosensitive drum,
discharging the image areas to a much lower
voltage (–100Vdc). The developing roller in the toner
cartridge has charged (–600Vdc) toner stuck
to it. As it rolls the toner toward the photosensitive drum,
the toner is attracted to (and sticks to) the
areas of the photosensitive drum that the laser has
discharged.
The image is then transferred from the drum to the paper at
its line of contact by means of the
corona wire (or corona roller) with a +600Vdc charge. The
static-eliminator strip removes the high,
positive charge from the paper, and the paper, now holding
the image, moves on. The paper then
enters the fuser where a fuser roller and the pressure
roller make the image permanent. The paper
exits the printer and the printer starts printing the next
page or returns to its ready state.
To help you remember the steps of the EP print process, in
order, remember them by the
first letters of each step, or CCWDTF. The most often used
mnemonic sentence for this
combination of letters is “Charlie Can Walk, Dance, and Talk
French.”
Printer Interfaces and Supplies
Interface Components
A printer’s interface is the collection of hardware and
software that allows the printer to
communicate with a computer. Each printer has at least one
interface, but some printers have
several, in order to make them more flexible in a
multiplatform environment. If a printer has
several interfaces, it can usually switch between them on
the fly so that several computers can print
at the same time.
There are several components to an interface, including its
communication type as well as the
interface software. Each aspect must be matched on both the
printer and the computer. For
example, an HP LaserJet 4L only has a parallel port.
Therefore, you must use a parallel cable as
well as the correct software for the platform being used
(e.g., a Macintosh HP LaserJet 4L driver if
you connect it to a Macintosh computer).
Communication Types
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When we say “communication types,” we’re actually talking
about the hardware technologies
involved in getting the printed information from the
computer to the printer. There are four major
types: serial, parallel, Universal Serial Bus (USB), and
network.
Serial
When computers send data serially, they send it one bit at a
time, one after another. The bits “stand
in line” like people at a movie theatre, waiting to get in.
Just as with modems, you must set the
communication parameters (baud, parity, start and stop bits)
on both entities—in this case the
computer and its printer(s) — before communication can take
place.
Parallel
When a printer uses parallel communication, it is receiving
data eight bits at a time over eight
separate wires (one for each bit). Parallel communication is
the most popular way of
communicating from computer to printer, mainly because it’s
faster than serial. A parallel cable
consists of a male DB-25 connector that connects to the
computer and a male 36-pin Centronics
connector that connects to the printer. Most of the cables
are shorter than 10 feet long. Keep
printer cable lengths to less than 10 feet. Some people try
to run printer cables more than
50 feet. After 10 feet, communications can become unreliable
due to cross talk.
Universal Serial Bus (USB)
The most popular type of printer interface as this book is
being written is the Universal Serial Bus
(USB). It is actually the most popular interface for just
about every peripheral. The convenience for
printers is that it has a higher transfer rate than either
serial or parallel and it automatically
recognizes new devices.
Network
Some of the newer printers (primarily laser and LED
printers) have a special interface that allows
them to be hooked directly to a network. These printers have
a network interface card (NIC) and
ROM-based software that allow them to communicate with
networks, servers, and workstations.
The type of network interface used on the printer depends on
the type of network the printer is
being attached to. For example, if you’re using a Token Ring
network, the printer should have a
Token Ring interface.
Infrared
With the explosion of Personal Digital Assistants (PDAs),
the need grew for printing under the
constraints they provide. The biggest hurdle faced by PDA
owners who need to print is the lack of
any kind of universal interface. Most interfaces were too
big and bulky to be used on handheld
computers like PDAs.
The solution was to incorporate the standardized technology
used on some remote controls:
infrared transmissions. Infrared transmissions are simply
wireless transmissions that use radiation
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in the infrared range of the electromagnetic spectrum. Many
laser printers (and some computers)
come with infrared transmitter/receivers (transceivers) so
that they can communicate with the
infrared ports on many handhelds. This allows the user of a
PDA, handheld, or laptop to print to
that printer by pointing the device at the printer and
initiating the print process.
As far as configuring the interface is concerned, very
little needs to be done. The infrared interfaces
are enabled by default on most computers, handhelds, and
printers equipped with them. The only
additional item that must be configured is the print driver
on the PDA, handheld, or computer. The
driver must be the correct one for the printer to which you
are printing.
Interface Software
Computers and printers can’t talk to each other by
themselves. They need interface software to
translate software commands into commands that the printer
can understand. There are two factors
to consider with interface software: the page description
language and the driver software. The
page description language determines how efficient the
printer will be at converting the information
to be printed into signals the printer can understand. The
driver software understands and controls
the printer. It is very important that you use the correct
interface software for the printer you are
using. If you use either the wrong page description language
or the wrong driver software, the
printer will print garbage, or possibly nothing at all.
Page Description Languages
A page description language works just as its name says it
does. It describes the whole page being
printed by sending commands that describe the text as well
as the margins and other settings. The
controller in the printer interprets these commands and
turns them into laser pulses (or pin strikes).
The first page description language was PostScript.
Developed by Adobe, it was first used in the
Apple LaserWriter printer. It made printing graphics fast
and simple. Here’s how PostScript works:
The PostScript printer driver “describes” the page in terms
of “draw” and “position” commands.
The page is divided into a very fine grid (as fine as the
resolution of the printer). When you want to
print a square, a communication like the following might
take place:
POSITION 1, 42%DRAW 10%POSITION 1, 64%DRAW10D% . . .
These commands tell the printer to draw a line on the page
from line 42 to line 64 (vertically). In
other words, a page description language tells the printer
to draw a line on the page, gives it the
starting and ending points, and that’s that. Rather than
send the printer the location of each and
every dot in the line and an instruction at each and every
location to print that location’s individual
dot, PostScript can get the line drawn with fewer than five
instructions. As you can see, PostScript
uses more or less English commands. The commands are
interpreted by the processor on the
printer’s controller and converted into the print control
signals.
Another page description language is the Printer Control
Language, or PCL.
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Currently in revision 5 (PCL 5), it was developed by
Hewlett-Packard for its LaserJet series of
printers as a competitor to PostScript. PCL works in much
the same manner as PostScript, but it’s
found mainly in Hewlett-Packard printers (including its
DeskJet bubble-jet printers). Other
manufacturers use PCL, however. In fact, some printers
support both page description languages
and will automatically switch between them.
The main advantage to page description languages is that
they move some of the processing from
the computer to the printer. With text-only documents, they
don’t offer much benefit. However,
with documents that have large amounts of graphics or that
use numerous fonts, page description
languages make the processing of those print jobs happen
much faster. This makes them an ideal
choice for laser printers. However, other printers can use
them as well (e.g., the aforementioned
DeskJets, as well as some dot-matrix printers).
Driver Software
The driver software controls how the printer processes the
print job. When you install a printer
driver for the printer you are using, it allows the computer
to print to that printer correctly
(assuming you have the correct interface configured between
the computer and printer).
When you need to print, you select the printer driver for
your printer from a preconfigured list. The
driver you select has been configured for the type, brand,
and model of printer as well as the
computer port to which it is connected. You can also select
which paper tray the printer should use,
as well as any other features the printer has (if
applicable). Also, each printer driver is configured to
use a particular page description language.
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