In computing, a printer is a peripheral machine which makes a persistent representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Different types of printers include 3D printers, inkjet printers, laser printers, and thermal printers.
HP LaserJet 5 printer
The Game Boy Pocket Printer, a thermal printer released as a peripheral for the Nintendo Game Boy
This is an example of a wide-carriage dot matrix printer, designed for 14-inch (360 mm) wide paper, shown with 8.5-by-14-inch (220 mm × 360 mm) legal paper. Wide carriage printers were often used in the field of businesses, to print accounting records on 11-by-14-inch (280 mm × 360 mm) tractor-feed paper. They were also called "132-column printers".
Liquid ink cartridge from Hewlett-Packard HP 845C inkjet printer
A difference engine is an automatic mechanical calculator designed to tabulate polynomial functions. It was designed in the 1820s, and was first created by Charles Babbage. The name difference engine is derived from the method of divided differences, a way to interpolate or tabulate functions by using a small set of polynomial co-efficients. Some of the most common mathematical functions used in engineering, science and navigation are built from logarithmic and trigonometric functions, which can be approximated by polynomials, so a difference engine can compute many useful tables.
The London Science Museum's difference engine, the first one actually built from Babbage's design. The design has the same precision on all columns, but in calculating polynomials, the precision on the higher-order columns could be lower.
Close-up of the London Science Museum's difference engine showing some of the number wheels and the sector gears between columns. The sector gears on the left show the double-high teeth very clearly. The sector gears on the middle-right are facing the back side of the engine, but the single-high teeth are clearly visible. Notice how the wheels are mirrored, with counting up from left-to-right, or counting down from left-to-right. Also notice the metal tab between "6" and "7". That tab trips the carry lever in the back when "9" passes to "0" in the front during the add steps (Step 1 and Step 3).
Fully operational difference engine at the Computer History Museum in Mountain View, California
