Writing a Simple Operating System — from Scratch

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 17 3.4.4 Using the Stack When on the topic of low-level computing, we o ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 18 ; ; A simple boot sector program that demonstrates the stack. ; mov ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 19 We can see from the assembly example that there is something going o ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 20 jmp my_print_function return_to_here: ; This label is our life -line ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 21 some_function: pusha ; Push all register values to the stack mov bx, ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 22 ; when to stop printing characters. GOODBYE_MSG: db ’Goodbye!’, 0 ; ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 23 Since we are printing a string to the screen, we might as well re-us ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 24 but a day-to-day operating systems would never sit comfortably in su ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 25 ; ; A simple boot sector program that demonstrates segment offsettin ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 26 Figure 3.8: Inside of a hard disk drive Figure 3.9: Cylinder, Head, ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 27 3.6.3 Using BIOS to Read the Disk As we will see a little later on, ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 28 ; actually read in AL is not equal to the number we expected. cmp al ...

CHAPTER 3. BOOT SECTOR PROGRAMMING (IN 16-BIT REAL MODE) 29 ; Read some sectors from the boot disk using our disk_read function ...

Chapter 4 Entering 32-bit Protected Mode It would be nice to continue working in the 16-bit real mode with which we have now bec ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 31 into the CPU, before setting a single bit in a special CPU control register to make ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 32 [bits 32] ; Define some constants VIDEO_MEMORY equ 0xb8000 WHITE_ON_BLACK equ 0x0f ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 33 based addressing, the best the programmer could do is this: mov [0xffff], ax which ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 34 and which, although not too disimilar as a concept, is not to be confused with exce ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 35 Granularity: 1, if set, this multiplies our limit by 4 K (i.e. 161616), so our 0xf ...

CHAPTER 4. ENTERING 32-BIT PROTECTED MODE 36 structure and how the flags are more conveniently defined using literal binary numb ...