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Mode 13h is the standard 256-color mode on VGA graphics hardware introduced in 1987 with the IBM PS/2. It has a resolution of 320 × 200 pixels . [ 1 ] It was used in computer games and art / animation software of the late 1980s and early to mid-1990s.
INT 13h is shorthand for BIOS interrupt call 13 hex, the 20th interrupt vector in an x86-based (IBM PC-descended) computer system.The BIOS typically sets up a real mode interrupt handler at this vector that provides sector-based hard disk and floppy disk read and write services using cylinder-head-sector (CHS) addressing.
Furthermore, on a modern x86 system, BIOS calls can only be performed in Real mode, or Virtual 8086 mode. v8086 is not an option in Long mode. This means that a modern operating system, which operates in Protected mode (32 bit), or Long mode (64 bit), would need to switch into real mode and back to call the BIOS - a hugely expensive operation.
640 × 480 monochrome (mode 11h) 320 × 200 in 256 colors (from a palette of 262,144; mode 13h) CGA compatible modes: 40 × 25 text mode with 8×8 pixel font (effective resolution of 320 × 200; mode 0/1h) 80 × 25 text mode with 8×8 pixel font (effective resolution of 640 × 200; mode 2/3h)
The term "Mode X" was coined by Abrash. Mode X is a variant of the 320 × 200 Mode 13h with the resolution increased to 320 × 240, giving square pixels instead of the slightly elongated pixels of Mode 13h. It is enabled by entering Mode 13h via an BIOS system call, then changing the values of several VGA registers. Additionally, Abrash enabled ...
Michael Abrash was a columnist in the 1980s for the magazine Programmer's Journal.The articles were collected in the 1989 book, Power Graphics Programming.His second book, Zen of Assembly Language Volume 1: Knowledge (1990), [13] is about writing efficient assembly code for the 16-bit 8086 processor, but was released after the 80486 CPU was already being used in IBM PC compatibles. [14]
For example, INT 13H will generate the 20th software interrupt (0x13 is nineteen (19) in hexadecimal notation, and the count starts at 0), causing the function pointed to by the 20th vector in the interrupt table to be executed. INT is widely used in real mode. In protected mode, INT is a privileged instruction. [1]
A BIOS Color Attribute is an 8 bit value where the low 4 bits represent the character color and the high 4 bits represent the background color.The name comes from the fact that these colors are used in BIOS interrupts, specifically INT 10h, the video interrupt.