Raster and vector font files begin with information that is common to both types of file and then continue with information that differs for each type. These font files are stored with an .FNT extension.
In Windows version 3.0 and later, the font-file header for raster and vector fonts includes six new members: dFlags, dfAspace, dfBspace, dfCspace, dfColorPointer, and dfReserved1. All device drivers support the fonts in Windows 2.x. However, not all drivers support those in versions 3.0 and later.
In Windows, font files for raster and vector fonts include the glyph table in the dfCharTable member, which consists of structures describing the bits for characters in the font file.The use of 32-bit offsets to the character glyphs in the dfCharTable member enables fonts to exceed 64K, the size limit of Windows 2.x fonts.
Because of their 32-bit offsets and potentially large size, the newer fonts are designed for use on systems that are running Windows versions 3.0 and later in protected (standard or 386-enhanced) mode and are using an 80386 (or higher) processor whose 32-bit registers can access the character glyphs. Typically, newer drivers use the newer version of a font only when both of these conditions are true.