The device context also defines the font that Windows uses when writing text to the client area. The default is a font called the ”system font“ or (using the WINDOWS.H identifier) SYSTEM_FONT. The system font is the font that Windows uses for text in caption bars, menus, and dialog boxes.
Under Windows 3, the system font is a variable-width font, which means that different characters have different widths. A ”W“ is wider than an ”i.“ In earlier versions of Windows, the system font was a fixed-pitch font in which all the characters had the same width.
The system font is a ”raster font,“ which means that the characters are defined as blocks of pixels. The floppy disks for the Windows installation include several system fonts in various sizes for use with different video display adapters.
When manufacturers of a new video board develop a new Windows display driver, they are also responsible for developing a new system font appropriate for the resolution of the display. Alternatively, the manufacturer might specify that one of the system font files supplied with the retail version of Windows be used. The system font must be designed so that at least 25 lines of 80-character text can fit on the display. That is the only guarantee you have about the relationship between screen size and font size in Windows.