Computer Modern is the family of typefaces used by default by the typesetting program TeX. It was created by Donald Knuth with his Metafont program, and was most recently updated in 1992. Computer Modern, or variants of it, remain very widely used in scientific publishing, especially in disciplines that make frequent use of mathematical notation.
The Computer Modern typefaces are described in great detail (including full source code) in the book Computer Modern Typefaces, volume E in the Computers and Typesetting series, which is unique in the history of font design: in Knuth's words, they "belong to the class of sets of books that describe precisely their own appearance."
As implied by the name, Computer Modern is a modern font. Modern, or "Didone", fonts have high contrast between thick and thin elements, and their axis of "stress" or thickening is perfectly vertical. Computer Modern, specifically, is based on Monotype Modern 8a, and like its immediate model it has a large x-height relative to the length of ascenders and descenders.
The most unusual characteristic of Computer Modern, however, is the fact that it is a complete type family designed with the Metafont system. The Computer Modern source files are governed by 62 distinct parameters, controlling the widths and heights of various elements, the presence of serifs or old-style numerals, whether dots such as the dot on the "i" are square or rounded, and the degree of "superness" in the bowls of lowercase letters such as "g" and "o". Computer Modern is by no means the only Metafont-designed typeface, but it is by far the most mature and widely used.
Knuth produced his original Computer Modern fonts using Metafont, a program that reads stroke-based definitions of glyphs and outputs ready-to-use fonts as bitmap image files.
The advance of publishing technology (PostScript, PDF, laser printers) has reduced the need for bitmap fonts. The preferred formats are now outline fonts such as Type 1, TrueType, or OpenType, which can be rendered efficiently at arbitrary resolution and using sophisticated anti-aliasing techniques by printer firmware or on-screen document viewers. Therefore, several other projects have ported the Computer Modern fonts into such formats. Some of these projects have also complemented Computer Modern with
- additional characters (euro, accented characters, Cyrillic and Greek script coverage)
- different font encodings (to overcome problems with Knuth's original 8-bit character sets)
- additional font style variants
Several such derivatives are now also widely used and included in TeX Live, a modern TeX distribution.
Computer Modern was first transformed to a PostScript Type 3 font format by BlueSky, Inc. in 1988, and then to Type 1 in 1992 to include font hinting. The Type 1 version has since then been donated to the AMS which distributes them freely under the Open Font License. It is found in most standard TeX distributions.
The Latin Modern implementation, maintained by Bogusław Jackowski and Janusz M. Nowacki, is now standard in the TeX community and was made through a Metafont/MetaPost derivative called METATYPE1. It was derived from the BlueSky Type 1 fonts, which were converted back into outline-based METATYPE1 programs, from which then the extended Type1 and OpenType Latin Modern fonts were developed.
The Type1 to METATYPE1 to Type 1 roundtrip conversion process involved in the production of the Latin Modern fonts did try to preserve the hinting information of the BlueSky fonts, however it added rounding errors that do affect the quality of the hinting at low pixel sizes. As a result, on-screen display of the Latin Modern fonts can result in a less even display of kerning and character heights than is the case with the BlueSky fonts.
- EC fonts — look much like Computer Modern, but have slightly different metrics. These were the first TeX fonts to use the "Cork encoding" (in LaTeX also known as T1 encoding) that provides precomposed glyphs for West-European languages. The original EC fonts were only available as Metafont generated bitmaps.
- TC fonts — the TeX Companion fonts provide a number of additional symbols commonly used in text.
- BaKoMa fonts — another automatically generated Type1 version of Computer Modern by Basil K. Malyshev.
- CM-super — a very large extension of Computer Modern, available in a variety of encodings. These fonts were automatically vectorized from Computer Modern or EC font bitmaps and therefore lack the hinting information in the BlueSky fonts.
- CM-LGC — a Latin, Greek, Cyrillic extension
- GUST  — adding many diacritics, and Vietnamese
- D. E. Knuth's apology for the updated font
- History of CM PostScript fonts
- A E F and T sized differently in lmodern package? • Fonts & Character Sets • LaTeX Community
- cm-super README file
- The Latin Modern (LM) Family of Fonts — GUST
- Donald E. Knuth, Computers and Typesetting Volume E: The Computer Modern Fonts, Addison-Wesley, Reading, Mass. 1986 Hardcover: ISBN 0-201-13446-2, Softcover: ISBN 0-201-60660-7
- Computer Modern-Super font package
- CM-LGC font package — Type 1 CM-based fonts for Latin, Greek and Cyrillic.
- Computer Modern typeface in TrueType format and OpenType.
- Computer Modern Unicode fonts X11 licensed
- Latin Modern fonts
- Comparison between CM-super and latin modern
- How to install Computer Modern fonts on OSX
- GUST Font Licenses (instance of LaTeX Project Public License).