What do they do?
Fonts are used by the Mac OS to render all text on the screen, and may also be used by (or downloaded to) the printer. Macs support three types: bitmap, PostScript and TrueType. Old ‘screen’ or ‘bitmap’ fonts become jaggy when scaled, but PostScript and TrueType contain vector outline information and can generate smooth letter forms at all sizes. While the software that renders TrueType fonts is built into the Mac OS, you need Adobe Type Manager (ATM) to render PostScript fonts on-screen and non-PostScript printers. This smoothing is different from the antialiasing available in the Appearance control panel in recent versions of the Mac OS. How do they work?
When software wishes to draw text, it tells the Mac OS which font it wants to use, where the text goes, and then sends the text to be drawn. The Mac OS looks through the fonts available in your Fonts folder, as well as those added by a utility such as Extensis Suitcase. Each character is looked up in the font file. ATM can also use special substitute fonts (Multiple Masters, or MM) to perform specialised font effects and to try to mimic fonts used in documents, such as Acrobat PDFs, but not available on your computer. What can go wrong with them?
Font substitution can easily get out of hand and produce unexpected results. This is common when you use TrueType fonts but have a PostScript printer: while the Mac OS may draw the screen image using the TrueType version, the printer may find a PostScript version and use that instead. Because TrueType and PostScript fonts with the same name may look different, your printed output may not match what you see on the screen. Newer versions of ATM may cause problems with existing applications and extensions. How can I upgrade them?
System fonts ship with the Mac OS, and third-party additions may be installed with software products (for example, music fonts with music notation programs) or bought separately. Many are available on CD-ROM from vendors such as Adobe, and can be licensed over the phone. Further info
Web sites with further information include Norman Walsh’s old but still useful cross-platform font FAQ at www.uni-mb.si/local/fontfaq/CF_1.HTM, Apple’s excellent collection of font tools and information at fonts.apple.com/Tools, and The Macintosh Font Vault, an extensive online catalogue of freeware and shareware fonts at www.erik.co.uk/font | 
