What is a printer?
A printer is a device that accepts text and graphic output from a computer and transfers the information to paper, usually to standard-size, 8.5" by 11" sheets of paper. Printers vary in size, speed, sophistication and cost. In general, more expensive printers are used for more frequent printing or high-resolution color printing.
Personal computer printers can be distinguished as impact or non-impact printers. Early impact printers worked something like an automatic typewriter, with a key striking an inked impression on paper for each printed character. The dot matrix printer, an impact printer that strikes the paper a line at a time, was a popular low-cost option.
The best-known non-impact printers are the inkjet printer and the laser printer. The inkjet sprays ink from an ink cartridge at very close range to the paper as it rolls by, while the laser printer uses a laser beam reflected from a mirror to attract ink (called toner) to selected paper areas as a sheet rolls over a drum.
Different types of printers
There are many different printer manufacturers available today, including Canon, Epson, Hewlett-Packard, Xerox and Lexmark, among many others. There are also several types of printers to choose from, which we'll explore below.
- Inkjet printers recreate a digital image by spraying ink onto paper. These are the most common type of personal printer.
- Laser printers are used to create high-quality prints by passing a laser beam at a high speed over a negatively charged drum to define an image. Color laser printers are more often found in professional settings.
- 3D printers are a relatively new printer technology. 3D printing creates a physical object from a digital file. It works by adding layer upon layer of material until the print job is complete and the object is whole.
- Thermal printers produce an image on paper by passing paper with a thermochromic coating over a print head comprised of electrically heated elements and produces an image in the area where the heated coating turns black. A dye-sublimation printer is a form of thermal printing technology that uses heat to transfer dye onto materials.
- All-in-one printers are multifunction devices that combine printing with other technologies such as a copier, scanner and/or fax machine.
- LED printers are similar to laser printers but use a light-emitting diode array in the print head instead of a laser.
- Photo printers are similar to inkjet printers but are designed specifically to print high-quality photos, which require a lot of ink and special paper to ensure the ink doesn't smear.
Older printer types
There are a few first-generation printer types that are outdated and rarely used today:
- Dot matrix printer: Dot matrix printing is an older impact printer technology for text documents that strikes the paper one line at a time. Dot matrix printers offer very basic print quality.
- Line printer: A line printer prints a single line of text at a time. While an older form of printing, line printers are still in use today.
Features to look for in a printer
The four printer qualities of most interest to users are:
- Color: Most modern printers offer color printing. However, they can also be set to print in black and white. Color printers are more expensive to operate since they use two ink cartridges -- one color and one black ink -- or toners that need to be replaced after a certain number of pages are printed. Printing ink cartridges or toner cartridges are comprised of black, cyan, magenta and yellow ink. The ink can be mixed together, or it may come in separate monochrome solid ink printer cartridges, depending on the type of printer.
- Resolution: Printer resolution -- the sharpness of text and images on paper -- is usually measured in dots per inch (dpi). Most inexpensive printers provide sufficient resolution for most purposes at 600 dpi.
- Speed: If a user does a lot of printing, printing speed is an important feature. Inexpensive printers print only about 3 to 6 sheets per minute. However, faster printing speeds are an option with a more sophisticated, expensive printer.
- Memory: Most printers come with a small amount of memory -- typically 2-16 megabytes- that can be expanded by the user. Having more than the minimum amount of memory is helpful and faster when printing out pages with large images.
Printer I/O interfaces
The most common I/O interface for printers had been the parallel Centronics interface with a 36-pin plug.
Nowadays, however, printers and computers are likely to use a serial interface, especially a USB or FireWire with smaller and less cumbersome plugs.
Printer languages are commands from the computer to the printer to tell the printer how to format the document being printed. These commands manage font size, graphics, compression of data sent to the printer, color, etc. The two most popular printer languages are Postscript and Printer Control Language.
Postscript is a printer language that uses English phrases and programmatic constructions to describe the appearance of a printed page to the printer. Adobe developed the printer language in 1985, and introduced new features such as outline fonts and vector graphics which can be printed with a plotter.
Printers now come from the factory with (or can be loaded with) Postscript support. Postscript is not restricted to printers. It can be used with any device that creates an image using dots such as screen displays, slide recorders and image-setters.
Printer Control Language (PCL)
PCL (Printer Control Language) is an escape code language used to send commands to the printer for printing documents. Escape code language has its name because the escape key begins the command sequence followed by a series of code numbers. HP originally devised PCL for dot matrix and inkjet printers.
Since its introduction, PCL has become an industry standard. Other manufacturers who sell HP clones have copied it. Some of these clones are very good, but there are small differences in the way they print a page compared to real HP printers.
In 1984, the original HP LaserJet printer was introduced using PCL, which helped change the appearance of low-cost printer documents from poor to exceptional quality.
A font is a set of characters of a specific style and size within an overall typeface design. Printers use resident fonts and soft fonts to print documents.
Resident fonts are built into the hardware of a printer. They are also called internal fonts or built-in fonts.
All printers come with one or more resident fonts. Additional fonts can be added by inserting a font cartridge into the printer or installing soft fonts on the hard drive. Resident fonts cannot be erased, unlike soft fonts.
Soft fonts are installed onto the hard drive or flash drive and then sent to the computer's memory when a document is printed that uses the particular soft font. Soft fonts can be downloaded from the internet or purchased in stores.