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CompTIA A+ Certification All-in-One Exam Guide

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Processing

When you click the Print button in an application, several things happen.

First, the CPU processes your request and sends a print job to an area of

memory called the print spooler. The print spooler enables you to queue up

multiple print jobs that the printer will handle sequentially. Next, Windows

sends the first print job to the printer. That’s your first potential bottleneck—

if it’s a big job, the OS has to dole out a piece at a time and you’ll see the

little printer icon in the notification area at the bottom right of your screen.

Once the printer icon goes away, you know the print queue is empty—all

jobs have gone to the printer.

Once the printer receives some or all of a print job, the hardware of the

printer takes over and processes the image. That’s your second potential

bottleneck, and it has multiple components.

Raster Images

Impact printers transfer data to the printer one character or one line at a time,

whereas laser printers transfer entire pages at a time to the printer. A laser

printer generates a raster image (a pattern of dots) of the page, representing

what the final product should look like. It uses a device (the laser imaging

unit) to “paint” a raster image on the photosensitive drum. Because a laser

printer has to paint the entire surface of the photosensitive drum before it can

begin to transfer the image to paper, it processes the image one page at a

time.

A laser printer uses a chip called the raster image processor (RIP) to

translate the raster image into commands to the laser. The RIP takes the

digital information about fonts and graphics and converts it to a rasterized

image made up of dots that can then be printed. An inkjet printer also has a

RIP, but it’s part of the software driver instead of onboard hardware circuitry.

The RIP needs memory (RAM) to store the data that it must process.

A laser printer must have enough memory to process an entire page. Some

pages printed at high resolution and containing very complex designs (lots of

fonts, complex formatting, high-resolution graphics, and so on) require more

memory. Insufficient memory will usually be indicated by a memory

overflow (“MEM OVERFLOW”) error. If you get a memory overflow or low

memory error, try reducing the resolution, printing smaller graphics, reducing

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