Hardware font
A hardware font, or VGA ROM font, contains a set of 256 monochrome and monospaced characters, the character width is always eight pixels. Each pixel is described as a single bit, on or off, and so each line is described as a single byte; therefore the byte size corresponds to the total number of lines. A single character's eight is 1/256 that amount. A character's description is the character height bytes found at the character number × character height offset in the file. There is no header or other form of meta-information.
This format is the one used by 
ZDoom uses it only for ANSI screen emulation and uses the one described in the file vga-rom-font.16 contained in zdoom.pk3. This font format cannot be used for in-game fonts.