The printer is a peripheral that allows you to make a print-out (on paper) of computer data.
There are several printer technologies, the most common of which are:
The printer is generally characterised by the following elements:
It is interesting to examine the printing cost per sheet. The size of the ink drop is especially important. The smaller the drop of ink, the lower the printing cost will be and the better the image quality will be. Some printers produce drops that are 1 or 2 picolitres.
Daisy wheel printers are based on typewriters. A matrix in the shape of a daisy contains "petals" that each have one raised character. To print the text, a ribbon of ink is placed between the daisy and the sheet of paper. When the matrix hits the ribbon it leaves ink on paper in the shape of the character on the petal.
These printers are obsolete because they are extremely noisy and very slow.
The dot-matrix printer (sometimes called a matrix printer or an impact printer) allows you to print documents on paper thanks to the "back and forth" motion of a carriage housing a print head.
The head is made up of tiny metal pins, driven by electromagnets, which strike a carbon ribbon called an "inked ribbon", located between the head and the paper.
The carbon ribbon scrolls by so that there is always ink on it. At the end of each line, a roller makes the sheet advance.
The most recent dot-matrix printers are equipped with 24-needle printer heads, which allows them to print with a resolution of 216 dpi (dots per inch).
The inkjet printer technology was originally invented by Canon. It is based on the principle that a heated fluid produces bubbles.
The researcher who discovered this had accidentally brought a syringe filled with ink into contact with a soldering iron. This created a bubble in the syringe that made the ink in the syringe shoot out.
Today's printer heads are made up of several nozzles (up to 256), equivalent to several syringes, which are heated up to between 300 and 400°C several times per second.
Each nozzle produces a tiny bubble that ejects an extremely fine droplet. The vacuum caused by the decrease in pressure creates a new bubble.
Generally, we make a distinction between the two different technologies:
The laser printer produce quality print-outs inexpensively at a high print speed. However, these printers are mostly used in professional and semi-professional settings because of their high cost.
Laser printers use a technology that is close to that used by photocopiers. A laser printer is mainly made up of an elecrostatically charge photosensitive drum that attracts the ink in order to make a shape that will be deposited on the sheet of paper.
How it works: a primary charge roller gives the sheets of paper a positive charge. The laser gives a positive charge to certain spots on the drum with a pivoting mirror. Then, negatively charged ink in powder form (toner) is deposited on the parts of the drum that were previously charged by the laser.
By turning, the drum deposits the ink on the paper. A heating wire (called a corona wire) finally attaches the ink to the paper.
Because laser printers do not have mechanical heads, they are quick and quiet.
There are two different types of laser printer technology: "carousel" (four passes) or "tandem" (single-pass).
Another printer technology competes with laser printers: LED (Light Emitting Diode) technology. With this technology, an electroluminescent diode printhead polarises the drum with a very fine light ray, making very small dots. This technology is particularly well adapted for obtaining high resolutions (600, 1,200 or 2,400 dpi).
Given that each diode is makes one point, print speed hardly affects resolution. Moreover, this technology lacks moving parts, which translates into less-expensive and more solid and reliable printers.
Page description language is the standard language that computers use to communicate with printers. Indeed, a printer must be able to interpret the information that a computer is sending to it.
The two main page description languages are:
There are control boxes called print servers that allow you to make a printer with a USB or parallel connection available to a whole network.