Common types of dot-based printers
Dot-matrix printers
These use an inked ribbon, like a typewriter, but instead of a single character-shaped head striking
the paper, a line of pins is used, each of which can strike the ribbon and hence dot the paper.
Horizontal resolution can be varied by altering the speed of the head across the paper, and vertical resolution can be improved by sending the head twice across the paper at a slightly different
position. So, dot-matrix printers can produce fast draft-quality output or slower ‘letter’-quality
output. They are cheap to run, but could not compete with the quality of jet and laser printers for
general office and home printing. They are now only used for bulk printing, or where carbon paper
is required for payslips, check printing, etc.)
Ink-jet and bubble-jet printers
These operate by sending tiny blobs of ink from the printhead to the paper. The ink is squirted at
pressure from an ink-jet, whereas bubble-jets use heat to create a bubble. Both are quite quiet in
operation. The ink from the bubble-jet (being a bubble rather than a droplet) dries more quickly
than the ink-jet and so is less likely to smear. Both approach laser quality, but the bubble-jet dots
tend to be more accurately positioned and of a less broken shape.
Laser printer
This uses similar technology to a photocopier: ‘dots’ of electrostatic charge are deposited on a
drum, which then picks up toner (black powder). This is then rolled onto the paper and cured by
heat. The curing is why laser printed documents come out warm, and the electrostatic charge is
why they smell of ozone! In addition, some toner can be highly toxic if inhaled, but this is more a
problem for full-time maintenance workers than end-users changing the occasional toner cartridge.
Laser printers give nearly typeset-quality output, with top-end printers used by desktop publishing
firms. Indeed, many books are nowadays produced using laser printers. The authors of this book
have produced camera-ready copy for other books on 300 and 600 dpi laser printers, although this
book required higher quality and the first edition was typeset at 1200 dpi onto special bromide