3.1.4 The graphics fields of Multiboot header

All of the graphics fields are enabled by flag bit 2. They specify the preferred graphics mode. Note that that is only a recommended mode by the OS image. Boot loader may choose a different mode if it sees fit.

The meaning of each is as follows:

mode_type

Contains ‘0’ for linear graphics mode or ‘1’ for EGA-standard text mode. Everything else is reserved for future expansion. Note that the boot loader may set a text mode even if this field contains ‘0’, or set a video mode even if this field contains ‘1’.

width

Contains the number of the columns. This is specified in pixels in a graphics mode, and in characters in a text mode. The value zero indicates that the OS image has no preference.

height

Contains the number of the lines. This is specified in pixels in a graphics mode, and in characters in a text mode. The value zero indicates that the OS image has no preference.

depth

Contains the number of bits per pixel in a graphics mode, and zero in a text mode. The value zero indicates that the OS image has no preference.