INT 10H
INT 10h, INT 10H or INT 16 is shorthand for BIOS interrupt call 10hex, the 17th interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides video services. Such services include setting the video mode, character and string output, and graphics primitives (reading and writing pixels in graphics mode).
To use this call, load AH with the number of the desired subfunction, load other required parameters in other registers, and make the call. INT 10h is fairly slow, so many programs bypass this BIOS routine and access the display hardware directly. Setting the video mode, which is done infrequently, can be accomplished by using the BIOS, while drawing graphics on the screen in a game needs to be done quickly, so direct access to video RAM is more appropriate than making a BIOS call for every pixel.
List of supported functions
| Function | Function code | Parameters | Return |
|---|---|---|---|
| Set video mode | AH=00h | AL = video mode | AL = video mode flag / CRT controller mode byte |
| Set text-mode cursor shape | AH=01h | CH = Scan Row Start, CL = Scan Row End
Normally a character cell has 8 scan lines, 0-7. So, CX=0607h is a normal underline cursor, CX=0007h is a full-block cursor. If bit 5 of CH is set, that often means "Hide cursor". So CX=2607h is an invisible cursor. Some video cards have 16 scan lines, 00h-0Fh. Some video cards don't use bit 5 of CH. With these, make Start>End (e.g. CX=0706h) |
|
| Set cursor position | AH=02h | BH = Page Number, DH = Row, DL = Column | |
| Get cursor position and shape | AH=03h | BH = Page Number | AX = 0, CH = Start scan line, CL = End scan line, DH = Row, DL = Column |
| Read light pen position (Does not work on VGA systems) | AH=04h | AH = Status (0=not triggered, 1=triggered), BX = Pixel X, CH = Pixel Y, CX = Pixel line number for modes 0Fh-10h, DH = Character Y, DL = Character X | |
| Select active display page | AH=05h | AL = Page Number | |
| Scroll up window | AH=06h | AL = lines to scroll (0 = clear, CH, CL, DH, DL are used),
BH = Background Color and Foreground color. BH = 43h, means that background color is red and foreground color is cyan. Refer the BIOS color attributes CH = Upper row number, CL = Left column number, DH = Lower row number, DL = Right column number |
|
| Scroll down window | AH=07h | like above | |
| Read character and attribute at cursor position | AH=08h | BH = Page Number | AH = Color, AL = Character |
| Write character and attribute at cursor position | AH=09h | AL = Character, BH = Page Number, BL = Color, CX = Number of times to print character | |
| Write character only at cursor position | AH=0Ah | AL = Character, BH = Page Number, CX = Number of times to print character | |
| Set background/border color | AH=0Bh, BH = 00h | BL = Background/Border color (border only in text modes) | |
| Set palette | AH=0Bh, BH = 01h | BL = Palette ID (was only valid in CGA, but newer cards support it in many or all graphics modes) | |
| Write graphics pixel | AH=0Ch | AL = Color, BH = Page Number, CX = x, DX = y | |
| Read graphics pixel | AH=0Dh | BH = Page Number, CX = x, DX = y | AL = Color |
| Teletype output | AH=0Eh | AL = Character, BH = Page Number, BL = Color (only in graphic mode) | |
| Get current video mode | AH=0Fh | AL = Video Mode, AH = number of character columns, BH = active page | |
| Write string (EGA+, meaning PC AT minimum) | AH=13h | AL = Write mode, BH = Page Number, BL = Color, CX = String length, DH = Row, DL = Column, ES:BP = Offset of string | |