Overstrike
Encyclopedia
In typography
Typography
Typography is the art and technique of arranging type in order to make language visible. The arrangement of type involves the selection of typefaces, point size, line length, leading , adjusting the spaces between groups of letters and adjusting the space between pairs of letters...

, overstrike is a method of printing character
Character (computing)
In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....

s that are missing from the printer
Printer
Printer may refer to:* Printer , a person or a company* Printer , a hardware device* Optical printer for motion picture films* The Moscow subway station Pechatniki, whose name means "Printers"...

's character set. It was widely used around the early 1990s. The character was created by placing one character on another one — for example, overstriking "L" with "-" resulted in printing a "Ł" character.

Many font
Font
In typography, a font is traditionally defined as a quantity of sorts composing a complete character set of a single size and style of a particular typeface...

 renderers in computer programs invent missing bold characters by overstriking the normal character with itself, slightly horizontally offset. The horizontal offset is essential, since unlike a typewriter
Typewriter
A typewriter is a mechanical or electromechanical device with keys that, when pressed, cause characters to be printed on a medium, usually paper. Typically one character is printed per keypress, and the machine prints the characters by making ink impressions of type elements similar to the pieces...

, where repeating a letter in exactly the same space will make it darker, most modern printers will not darken repeated "strikes" to the same space. Actual bold fonts are designed with some features thicker and others the same size as a regular font, so the use of this "fake bold" is considered undesirable from a typographic point of view; some typesetting
Typesetting
Typesetting is the composition of text by means of types.Typesetting requires the prior process of designing a font and storing it in some manner...

 programs, including Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

's native font chooser and text renderer, go so far as to refuse to fake bold in this way.
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