ocr: IBM PC INTERRUPT IBM PC ROM BIOS VECTOR TABLE Int # Hndlr Addr BIOS Routines 1-- Hard- ware 0x08: >I Clock Tick ints Ox09: >I Key Stroke - Soft- Ox14: Read/Write Serial Ports I ware 0x15: Read/Write Cassette ints Ox16: - /->1 Read Keyboard Ox17: ->1 Write Printer V V Patch Routines call bios routine---/ ----receive key ready message (if any) I send message to key_ready mailboxl call bios routine---/ / / key_ready mailbox: <k_r> L/ To prevent tasks from wasting processoT time waiting for keystrokes, we can intercept the TBM PC's BIOS interrupt routznes, to check and signal when a keystroke is a ...
