Type 1 and Type 3 fonts, though introduced by Adobe in 1984 as part of the PostScript page description language, did not see widespread use until March 1985 when the first laser printer to use the PostScript language, the Apple LaserWriter, was introduced.
Although originally part of PostScript, Type 1 fonts used a simplified set of drawing operations compared to ordinary PostScript (programmatic elements such as loops and variables were removed, much like PDF), but Type 1 fonts added "hints" to help low-resolution rendering.
The cost of the licensing was considered very high at this time, and Adobe continued to stonewall on more attractive rates.
For users wanting to preview these typefaces on an electronic display, small versions of a font need extra hints and anti-aliasing to look legible and attractive on screen.
Type 0 is a "composite" font format – as described in the PostScript Language Reference Manual, 2nd Edition.
[3] Support for Type 1 fonts in Adobe Photoshop was discontinued with the release of version 23.0 of the product in October 2021.
Type 32 is used for downloading bitmap fonts to PostScript interpreters with version number 2016 or greater.
The bitmap characters are transferred directly into the interpreter's font cache, thus saving space in the printer's memory.
The out-of-sequence choice of the number 42 is said to be a jesting reference to The Hitchhiker's Guide to the Galaxy, where 42 is the Answer to Life, the Universe, and Everything.
They include the 13 font styles defined by PostScript Level 1, along with ITC Zapf Dingbats.
These fonts also contain currency symbols (cent, dollar, euro, florin, pound sterling, yen), standard ligatures (fi, fl), common fractions (1/4, 1/2, 3/4), common mathematics operators, superscript numerals (1,2,3), common delimiters and conjoiners, and other symbols (including daggers, trademark, registered trademark, copyright, paragraph, litre and estimated symbol).
Compared to the ISO-Adobe character set, Western 2 also adds 17 additional symbol characters: euro, litre, estimated, omega, pi, partialdiff, delta, product, summation, radical, infinity, integral, approxequal, notequal, lessequal, greaterequal, and lozenge.
Fonts with an Adobe Western 2 character set support most western languages including Afrikaans, Basque, Breton, Catalan, Danish, Dutch, English, Finnish, French, Gaelic, German, Icelandic, Indonesian, Irish, Italian, Norwegian, Portuguese, Sami, Spanish, Swahili and Swedish.
Fonts with an Adobe CE character set also include the characters necessary to support the following central European languages: Croatian, Czech, Estonian, Hungarian, Latvian, Lithuanian, Polish, Romanian, Serbian (Latin), Slovak, Slovenian and Turkish.
Fonts with an ISO-Adobe character set support most western languages including: Afrikaans, Basque, Breton, Catalan, Danish, Dutch, English, Finnish, French, Gaelic, German, Icelandic, Indonesian, Irish, Italian, Norwegian, Portuguese, Sami, Spanish, Swahili and Swedish.
CID-keyed fonts often reference "character collections," static glyph sets defined for different language coverage purposes.
Although in principle any font maker may define character collections, Adobe's are the only ones in wide usage.
CID-keyed fonts may be made without reference to a character collection by using an "identity" encoding, such as Identity-H (for horizontal writing) or Identity-V (for vertical).
Adobe ClearScan technology (as from Acrobat 9 Pro) creates custom Type1-CID fonts to match the visual appearance of a scanned document after optical character recognition (OCR).
[11] As a result of the above changes, Adobe no longer guarantees metric compatibility between Type 1 and OpenType fonts.
Adobe then developed the CID-keyed font file format which was designed to offer better performance and a more flexible architecture for addressing the complex Asian-language encoding and character set issues.
The formats are sufficiently similar that a compliant parser can parse AFM, ACFM, and AMFM files.
PFA is the preferred format for Type 1 fonts used in UNIX environments, and usually carries a ".PFA" file name extension.
The first section of the file is called the clear text portion, and begins constructing those data structures that define the font in the PostScript interpreter; the information here are things Adobe in the 1980s were comfortable having public, and much of it would be present also in the companion AFM file.
The following encrypted portion is again PostScript code for finishing constructing the font data structures—a lot of it consists of charstrings, which is rather a kind of bytecode, but at the font definition stage those are merely data stored in the font—even if that code is encrypted (which produces arbitrary byte values) and then hex-encoded to ensure the overall ASCII nature of the file.
The data structures created here are marked noaccess to make them inaccessible for subsequent PostScript code.
The PFB format is a lightweight wrapper to allow more compact storage of the data in a PFA file.
Printer Font Metric (PFM) is a binary version of AFM, usually carrying ".PFM" file name extension.
Both of those documents are part of the Windows 3.1 Device Development Kit (DDK), which is still available (October 2008) to MSDN subscribers.
.MMM files are used for the metric data needed by multiple master fonts for the Windows environment.