PC BIOS

Real mode 16-bits 8086 compatible ROM routines available at boot time for a PC since 1983. The working of it is best illustrated by calling them in assembler.

INT 10h Video

Set video mode:

MOV AH, 0x00
MOV BL, 0x03
INT 0x10

┌─────────────────┬────────┬────────────┬────────┐
│ Function        │ Code   │ Parameters │ Return │
├─────────────────┼────────┼────────────┼────────┤
│ Video Mode      │ AH=0h  │ BL=mode    │        │
├─────────────────┼────────┼────────────┼────────┤
│ Print Teletype  │ AH=0Eh │ AL=char    │        │
└─────────────────┴────────┴────────────┴────────┘