INT 16H
INT 16h, INT 0x16, INT 16H or INT 22 is shorthand for BIOS interrupt call 16hex, the 23rd interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides keyboard services. This interruption is responsible for control of the PC keyboard.
Features
This interruption is responsible for obtaining basic keyboard functionality, i.e. is responsible for collecting the keystrokes, obtain the status of the buffer of keyboard, etc. The standard encoding of the keyboard that offers the INT 16 h is a US keyboard. To adapt the coding of the INT 16h to another type of keyboard (for example, an international keyboard), the code must analyze the scan-code of the key pressed, and then perform suitable interpreting.
For keyboards with 101 letters or more, there are some keys that INT 16h interprets as expanded keys, which have a scan-code that is different from normal keys (e.g., key pause).
List of services of the INT 16 h
| Function | Function code(AH) | Device |
|---|---|---|
| Read key press | 00h | Keyboard |
| Get the State of the keyboard buffer | 01h | Keyboard |
| Get the State of the keyboard | 02h | Keyboard |
| Establish repetition factor | 03h | Keyboard |
| Keyboard Click adjustment | 04h | Keyboard |
| Simulate a keystroke | 05h | Keyboard |
| Get the ID of the keyboard | 0Ah | Keyboard |
| Read expanded keyboard character | 10h | Expanded keyboard |
| Obtain status of the expanded keyboard buffer | 11h | Expanded keyboard |
| Get expanded keyboard status | 12h | Expanded keyboard |
INT 16h Detailed Function List
| Function | Function code(AH) | Device | Inputs | Return | |
|---|---|---|---|---|---|
| Read key press | 0h | Keyboard | None | AH[1] = Scan code of the key pressed down | AL = ASCII character of the button pressed |
| Get the State of the keyboard buffer | 1h | Keyboard | None | AH = Scan code, ZF = 0 if key pressed down | AL = ASCII character, AX = 0 if no Scan codes |
| Get the State of the keyboard | 2h | Keyboard | None | AH = BIOS Keyboard flags | |
| Establish repetition factor | 3h | Keyboard | AL = Mode, BH = Repeat delay (if AL = 5), BL = Typematric rate | None | |
| Keyboard Click adjustment | 4h | Keyboard | AL = 0 (off) or 1 (on) | None | |
| Simulate a keystroke | 5h | Keyboard | CH = Scan code, CL = ASCII Character | AL = 0 If successful, 1 otherwise | |
| Get the ID of the keyboard | Ah | Keyboard | None | AL = Keyboard Id | |