Readings in the text

• Section 5.4 - Software Interrupts
• Sections 5.6, 5.7 - BIOS Keyboard & Video Services
• Section 10.2 - String Instructions
• Section 14.2 - Input / Output
• Section 15.4 - Interrupt Handling
• Section 15.5 - Floating Point Operations
• Handout - How Interrupts Work

Topics

• General
  • Three sides of the OS (HW, API, UI)
  • Different ways of obtaining services (libraries, OS, BIOS, HW)
  • Memory diagram (IVT, BDA, VRAM, ROM BIOS)
• Boot Loaders
  • Power-up process
  • Structure of a boot sector
  • Boot sector signature 55AAh
  • BIOS Parameter Block
• Interrupts
  • Hardware interrupts (HW devices)
  • Software interrupts (OS/BIOS services)
  • Programmable Interrupt Controller (master and slave)
  • Interrupt Vector Table (at 0000:0000)
  • Interrupt Service Routines
  • IRQ number vs. int number
  • What happens in response to an interrupt
  • Disabling and enabling interrupts (cli / sti)
  • Critical sections
  • Setting your own ISR
  • End of Interrupt command (20h to port 20h)
• Timers
  • Different kinds of timers (PIT CHN0, PIT CHN2, TSC, RTC)
  • Programmable Interval Timer
  • Crystal Oscillator and the magic number 1193182
  • Three channels of the PIT and their purpose
  • Timer tick interrupt (hardware, IRQ 0, int 8, 18.2 times/sec)
  • Timer tick interrupt responsibilities
  • User-defined timer tick interrupt (software, int 1Ch, 18.2 times/sec)
  • Timer tick count in BDA (0040:006Ch)
  • Determining time of day by the tick count
  • Programming the PIT (ports 61h, 43h, 40h, 41h, 42h)
• Speaker
  • Generating sound
• Input Devices
  • Keyboard Food Chain
  • Keyboard data in BDA (head, tail, queue, start, end)
  • Keyboard Controller access (port 64h, 60h)
  • Scancodes vs. ASCII codes
  • Make codes vs. break codes
  • Writing a keyboard ISR
• Disks and File Systems
  • Heads, cylinders (tracks), records (sectors)
  • DOS sectors and clusters
  • FAT file system structure
  • Directory entry, attributes, date, time
  • File Allocation Table structure
• Other
  • Writing directly to video memory
  • Floating point instructions
  • String instructions