A font, also known as a typeface, is a collection of characters, such as letters, numerals, punctuation marks and other symbols, that possess common design characteristics. Each character in such a font is described in the same way as a graphic, either as a bitmap or as a vector image.
A bitmap font is usually limited to the resolution of a computer’s monitor, typically 72 dpi for the Mac OS or 96 dpi for the Windows system, both of which are inadequate for printing. Unfortunately, such fonts become distorted when resized. For example, a 12-point bitmap font when expanded to a 24-point size appears to have half the resolution, making it look very jagged.
A vector font, on the other hand, isn’t designed for a specific resolution, which means that it looks good at any size. However, vector fonts also require more computer processing, which means that some operating systems retain bitmap fonts, also known as screen fonts, for on-screen presentation, whilst using vector fonts for printing. Unfortunately, this can worsen the inherent disparity in character positioning that can occur between text on the screen and that produced on paper.
Various file formats are used to describe a complete font as vector graphics. Although some of these are more common on specific computer platforms, they’re not mutually exclusive. For example, the Mac OS lets you use both TrueType and PostScript fonts at the same time.
PostScript fonts, as developed by Adobe, were introduced to the Classic Mac OS alongside the Apple’s first LaserWriter printer, and later appeared in the Windows system. Unlike TrueType, these fonts always employ separate vector information for each typeface within a font family, thereby providing the high-quality required for professional desktop publishing (DTP) work.
Mac OS X appears to accept any PostScript Type 1 files: unlike the Classic OS, bitmap fonts aren’t required for the screen display. And although multiple-master PostScript fonts aren’t supported by the system, such fonts can be placed in the
Fonts folder of any application that needs them.
As with all system files in the Classic Mac OS, font files must have the necessary information contained in their resource forks. This means that fonts designed for a Windows machine can’t be used directly in Classic or vice versa, although conversion of such files may be possible.
In the Classic Mac OS, the PostScript files that describe a font must be accompanied by a font suitcase, which contains a font description, also known as a
FOND resource, as well as the bitmap fonts for on-screen display. However, if you’re running Mac OS 9.x, a suitable version of ATM and an application that is compatible with Apple Type Services for Unicode Imaging (ATSUI), you don’t need a suitcase, as the system’s Font Manager synthesises the necessary
FOND resource. Sadly, very few Classic Mac OS applications actually work with ATSUI, the latter having been introduced to replace the abortive system known as QuickDraw GX (see below).
.afm. This file can be used by a font-editing application, allowing you to modify a font or to copy elements of one font into another.
As already mentioned, the PostScript files for Windows are different to those for the Classic Mac OS: those used in Windows are usually identified by a filename extension of
.pfm. This can be used by a font-editing application, allowing you to modify a font or to copy elements of a font into another file.
This format, originally devised by Apple, was introduced to the Classic Mac OS following the arrival of PostScript, although it later migrated to Windows. It allows high-quality fonts to be reproduced on a non-PostScript printer, providing thousands of characters and allowing any degree of resizing.
Mac OS X accepts most fonts, including the
.ttc TrueType files used in the Windows system. The latter are sometimes known as data fork TrueType fonts to distinguish them from the font suitcases of the Classic Mac OS. However, fonts of this variety that have a
.dfont filename extension can only be used by the system itself, not by standard applications.
Traditional fonts in the Classic Mac OS must have all the necessary information in the resource fork of a special file known as a font suitcase. This kind of document may also contain the bitmap fonts for on-screen display, although later versions of the system only require TrueType resources. Applications that support ATSUI (see above), which is provided as part of Mac OS 9.x, also accept non-suitcase fonts, such as the
.ttc TrueType files used in the Windows system.
This development of TrueType, regrettably abandoned by Apple in later versions of the Classic Mac OS, accommodates intelligent ligatures, pair kerning and up to 65,000 different characters.
The TrueType files for Windows have extensions of
.ttc, the latter being a font collection.
This modern format, developed by Microsoft and Adobe for use on Windows, Mac OS and other computers, is designed to replace the older systems described above. With OpenType, applications can adjust the shape of characters or replace selected symbols by swashes. Similarly, specified groups of characters can be replaced by ligatures and artificial fractions can be replaced by true fractions, assuming the latter exist in the font. The format also supports alternate glyphs.
The information for each font is kept in an OpenType Font (OTF) file, which is identified by an
.otf filename extension: such files can contain a TrueType or PostScript font description, or both. Unicode character coding is used, accommodating up to 65,000 different characters for world languages: rather better than the PostScript Type 1 format that only allows 256 characters.
Each OTF contains embedding permissions that determine how the font can be embedded into certain documents, such as a PDF or EPSF file. The permissions are as follows:-
|None||Font can only be used from the system|
|Print and preview||User can’t modify document containing font|
|Editable||User can modify document containing font|
|Installable||Font can be copied out of the document|
.otf files can be used in Mac OS X.
Generally speaking, OpenType fonts aren’t available in the Classic Mac OS. However, if you’re running Mac OS 9.x and an ATSUI-compatible application you can use such fonts.
.otf files can be used in Windows.
This system, developed by Bitstream, employs similar technology to OpenType, but is specially designed for Netscape, the popular Web browser for the Internet.
Most modern applications are available in versions that can be used on various kinds of computers. In addition, the documents that they produce can be transferred between different machines whilst maintaining the correct character set and line endings.
The actual fonts used in your work aren’t conveyed inside such documents, mainly because this would make the files far too large. Instead, the available fonts form part of each machine’s operating system. The fonts that you employ are then identified by a list of font names stored in each document.
Unfortunately, there isn’t a standard set of fonts used on any computer, let alone across different operating systems. At best, this means that a document can end up with the wrong fonts, resulting in incorrect line wrap and text positioning, as well as a different appearance. At worst, none of the fonts are recognised, making it difficult to restore the original look of the document.
Some applications, such as Adobe Reader (Adobe), incorporate a font substitution system that replaces any missing fonts by generic fonts that have a similar appearance. Sadly, there are few other programs with this feature. However, in HTML documents, as used for Web pages, you can include a list of suitable fonts, as in this example from a Cascading Style Sheet (CSS) file:-
which means that the recipient’s computer first looks for the
Geneva font. If this is missing it then looks for
Verdana. Failing both of these, it’ll use a generic font with a san-serif style.
The Mac OS and Windows operating systems employ fonts that have different names. The following table shows the nearest equivalents for the most common fonts used in each platform:-
|Geneva||MS Sans Serif|
|New York||MS Serif|
|Times||Times New Roman|
|Palatino||Times New Roman|
Mac OS is designed around displays that have a resolution of 72 dpi or ppi, whereas Windows is based on 96 dpi. Hence font sizes can appear differently, as shown in this table:-
|14 point||12 point|
|18 point||14 point|
|24 point||18 point|
|30 point||24 point|
©Ray White 2004.