In typography, the point is the smallest unit of measure. It is used for measuring font size, leading, and other items on a printed page. The size of the point has varied throughout printing's history. Since the 18th century, the size of a point has been between 0.18 and 0.4 millimeters. Following the advent of desktop publishing in the 1980s and 1990s, digital printing has largely supplanted the letterpress printing and has established the desktop publishing (DTP) point as the de facto standard. The DTP point is defined as 1⁄72 of an inch (or exactly 0.3527 mm) and, as with earlier American point sizes, is considered to be 1⁄12 of a pica. In metal type, the point size of a font describes the height of the metal body on which that font's characters were cast. In digital type, letters of a computer font are designed around an imaginary space called an "em square". When the point size of a font is specified, the font is scaled so that its em square has a side length of that particular length in points. Although the letters of a font usually fit within the font's em square, there is not necessarily any size relationship between the two, so the point size does not necessarily correspond to any measurement of the size of the letters on the printed page.
History The point was first established by the Milanese typographer, Francesco Torniella da Novara (c. 1490 – 1589) in his 1517 alphabet, L'Alfabeto. The construction of the alphabet is the first based on logical measurement called "Punto", which corresponds to the ninth part of the height of the letters or the thickness of the principal stroke.
Notations A measurement in points can be represented in three different ways. For example, 14 points (1 pica plus 2 points) can be written:
1P⁄2p (12 points would be just "1P⁄ ")—traditional style 1p2 (12 points would be just "1p")—format for desktop 14pt (12 points would be "12pt" or "1pc" since it is the same as 1 pica)—format used by Cascading Style Sheets defined by the World Wide Web Consortium.
Varying standards
There have been many definitions of a "point" since the advent of typography. Traditional continental European points at about 0.375 mm are usually a bit larger than English points at around 0.350 mm.
French points
The Truchet point, the first modern typographic point, was 1⁄12 of a French line (French: ligne). It was invented by the French Catholic priest Sébastien Truchet for the Bignon Commission (1693–1718). (During the metrication of France amid its revolution, a 1799 law declared the meter to be exactly 443.296 French lines long. The Truchet point therefore became equal to 15625⁄83118 mm or about 0.187986 mm.)
The Fournier point was established by Pierre Simon Fournier in 1737. The system of Fournier was based on a different French foot of about 298 mm (11.7 in). With the usual convention that 1 foot equals 12 inches, 1 inch (French: pouce) was divided into 12 lines (lignes) and 1 line was further divided into 6 typographic points (points typographiques). One Fournier point is about 0.0135 English inches.
Fournier printed a reference scale of 144 points over two inches; however, it was too rough to accurately measure a single point. The Fournier point did not achieve lasting popularity, despite being revived by the Monotype Corporation in 1927. It was still a standard in Belgium, in parts of Austria, and in Northern France at the beginning of the 20th century. In Belgium, the Fournier system was used until the 1970s and later. It was called the "mediaan"-system.
The Didot point, established by François-Ambroise Didot in 1783, was an attempt to improve the Fournier system. He did not change the subdivisions (1 inch = 12 subdivisions = 72 points), but defined it strictly in terms of the royal foot, a legal length measure in France: the Didot point is exactly 1⁄864 of a French foot or 1⁄72 of a French inch, that is (by 1799) 15625⁄41559 mm or about 0.375972 mm. Accordingly, one Didot point is exactly two Truchet points. However, 12 Fournier points turned out to be 11 Didot points, giving a Fournier point of about 0.345 mm; later sources state it as being 0.34875 mm. To avoid confusion between the new and the old sizes, Didot also rejected the traditional names, thus parisienne became corps 5, nonpareille became corps 6, and so on. The Didot system prevailed because the French government demanded printing in Didot measurements. Approximations were subsequently employed, largely owing to the Didot point's unwieldy conversion to metric units (the divisor of its conversion ratio has the prime factorization of 3×7×1979). In 1878, Hermann Berthold defined 798 points as being equal to 30 cm, or 2660 points equalling 1 meter: that gives around 0.376 mm to the point. A more precise number, 0.376065 mm, sometimes is given; this is used by TeX as the dd unit. This has become the standard in Germany and Central and Eastern Europe. This size is still mentioned in the technical regulations of the Eurasian Economic Union.
Metric points pdfTEX, but not plain TeX nor LaTeX, also supports a new Didot point (nd) at 3⁄8 mm or 0.375 mm and refers to a not-further-specified 1978 redefinition for it.
The French National Print Office adopted a point of 2⁄5 mm or 0.400 mm in about 1810 and continues to use this measurement today (though "recalibrated" to 0.39877 mm). Japanese and German standardization bodies instead opted for a metric typographic base measure of exactly 1⁄4 mm or 0.250 mm, which is sometimes referred to as the quart in Japan. The symbol Q is used in Japanese after the initial letter of quarter millimeter. Due to demand by Japanese typesetters, CSS adopted Q in 2015.
… excerpt ends here. Continue reading the full article.
