About Windows NT Fonts

Windows NT provides three basic font technologies. The differences between them reflect the way that the glyph (or symbol) for each character is stored in the respective font-resource file.

• Raster fonts are stored in files as bitmaps and are rendered as an array of dots for display on the screen and printing on paper. Raster fonts cannot be cleanly scaled or rotated.

• Vector fonts are outline fonts and are rendered from a mathematical model, where each character is defined as a set of lines drawn between points. Vector fonts can be scaled to any size or aspect ratio.

• TrueType fonts are outline fonts and are rendered from line and curve commands as well as a collection of hints. Windows uses the line and curve commands to define the outline of a character or symbol. Windows uses the hints to adjust the length of the lines and shapes of the curves when scaling or rotating the character. TrueType fonts can be scaled and rotated.

Note

Windows NT also supports Adobe Type 1 fonts native on PostScript printers and via conversion to TrueType for screen and non-PostScript devices. However, no Adobe Type 1 fonts are included with Windows NT.

In addition, Windows NT fonts are described according to the output device:

• Screen fonts are font descriptions that Windows NT uses to represent characters on display devices. (TrueType fonts act as both screen and printer fonts.)

• Printer fonts are the font descriptions used by the printer to create a font. Windows NT–based applications can use three kinds of printer fonts: device fonts, downloadable soft fonts, and printable screen fonts, as described in "Printer Fonts and Windows NT," later in this chapter.

Because the bitmaps for each glyph in a raster font are designed for a specific resolution of device, raster fonts are generally considered to be device dependent. Vector fonts, on the other hand, are not device dependent, because each glyph is stored as a collection of scalable lines. However, vector fonts are generally drawn more slowly than raster or TrueType fonts. TrueType fonts provide both relatively fast drawing speed and true device independence. By using the hints associated with a glyph, a developer can scale the characters from a TrueType font up or down and still maintain their original shape.

As previously mentioned, the glyphs for a font are stored in a font-resource file. A font-resource file is actually a Windows library that contains only data—no code. For raster and vector fonts, this data is divided into two parts: a header describing the font's metrics and the glyph data. A font-resource file for a raster or vector font is identified by the .fon filename extension.

In 16-bit Windows TrueType fonts had two files for each font: The first file contains a relatively short header and the second contains the actual font data. The first file is identified by a .fot extension and the second is identified by a .ttf extension. Windows NT 4.0 still supports this for backwards compatibility, but doesn't require the .fot file. AddFontResource can be called from applications directly for a .ttf file.

As shown in the following illustration, you can identify the different fonts in Windows NT–based applications by the icons associated with the font name.

The next sections describe raster, vector, TrueType, and Adobe Type 1 fonts. Later sections in this chapter discuss screen fonts and printer fonts used by Windows NT.