(^412) PC Hardware: A Beginner’s Guide
codes used to create the letters, numbers, special characters, graphics, print styles, and
other document effects, such as tabs, line feeds, page (form) feeds, etc. This data file is
stored in the operating system’s print queue. The print queue is the buffer that holds the
print data files waiting to be sent to the printer. If the printer is not in use, the file is sent to
the printer immediately. However, if the printer is in use, the print data file will be held
until the printer is available and no other print jobs are in the queue ahead of it.
Print Buffer
When the printer is available, the print data file is transferred to the dot matrix printer
and is stored in its buffer. The printer’s buffer is needed because it takes much longer to
print a document than it does to transfer it from the computer to the printer. By storing
the print data file in the printer’s buffer, the computer is released to perform other tasks.
Early printers did not have print buffers and the printer had to ask the computer for each
print command, which tied up both the computer and the printer until the document was
completed.
Print buffers on dot matrix printers typically hold between 8 to 60 kilobytes (KB) of
data, depending on the age, manufacturer, and model of the printer. Dot matrix printers
with enhanced graphics or extended font capabilities tend to have larger print buffers.
The size of a dot matrix printer’s print buffer is commonly listed right along with its print
speed as one of its major features. More is always better.
When the entire file has been transferred into the print buffer or if the print buffer fills
up, the printer tells the computer to quit sending the data until the buffer has space.
While this is going on, the data in the buffer is fed to the printer’s processor that interprets
the codes and commands for printing. As the processor reads off the data in the buffer,Figure 17-9. A dot matrix printer. Photo courtesy of OkiData Americas, Inc.