; ==================================================================
; MikeOS -- The Mike Operating System kernel
; Copyright (C) 2006 - 2022 MikeOS Developers -- see doc/LICENSE.TXT
;
; This is loaded from the drive by BOOTLOAD.BIN, as KERNEL.BIN.
; First we have the system call vectors, which start at a static point
; for programs to use. Following that is the main kernel code and
; then additional system call code is included.
; ==================================================================


	BITS 16
	CPU 386				; pusha offsets depends on a 386 or better
					; FS and GS require a 386 or better

	%DEFINE CRAWOS_VER '0.0.2'	; OS version number
	%DEFINE CRAWOS_API_VER 1	; API version for programs to check


	; This is the location in RAM for kernel disk operations, 24K
	; after the point where the kernel has loaded; it's 8K in size,
	; because external programs load after it at the 32K point:

	disk_buffer	equ	24576


; ------------------------------------------------------------------
; OS CALL VECTORS -- Static locations for system call vectors
; Note: these cannot be moved, or it'll break the calls!

; The comments show exact locations of instructions in this section,
; and are used in programs/mikedev.inc so that an external program can
; use a CrawOS system call without having to know its exact position
; in the kernel source code...

os_call_vectors:
	jmp os_main			; 0000h -- Called from bootloader
	jmp os_print_string		; 0003h
	jmp os_read_input
	jmp os_display_input
	jmp os_start_cli


; ------------------------------------------------------------------
; START OF MAIN KERNEL CODE

os_main:
	cli				; Clear interrupts
	mov ax, 0
	mov ss, ax			; Set stack segment and pointer
	mov sp, 0FFFFh
	sti				; Restore interrupts

	cld				; The default direction for string operations
					; will be 'up' - incrementing address in RAM

	mov ax, 2000h			; Set all segments to match where kernel is loaded
	mov ds, ax			; After this, we don't need to bother with
	mov es, ax			; segments ever again, as MikeOS and its programs
	mov fs, ax			; live entirely in 64K
	mov gs, ax

	cmp dl, 0
	je no_change
	mov [bootdev], dl		; Save boot device number
	push es
	mov ah, 8			; Get drive parameters
	int 13h
	pop es
	and cx, 3Fh			; Maximum sector number
	mov [SecsPerTrack], cx		; Sector numbers start at 1
	movzx dx, dh			; Maximum head number
	add dx, 1			; Head numbers start at 0 - add 1 for total
	mov [Sides], dx

no_change:
	call os_clear_screen
	call os_start_cli

bootdev db 0
SecsPerTrack dw 18
Sides dw 2

; ------------------------------------------------------------------
; SYSTEM VARIABLES -- Settings for programs and system calls


	; Time and date formatting

	fmt_12_24	db 0		; Non-zero = 24-hr format

	fmt_date	db 0, '/'	; 0, 1, 2 = M/D/Y, D/M/Y or Y/M/D
					; Bit 7 = use name for months
					; If bit 7 = 0, second byte = separator character


; ------------------------------------------------------------------
; FEATURES -- Code to pull into the kernel

	%INCLUDE "features/screen.asm"
	%INCLUDE "features/cli.asm"
	%INCLUDE "features/power.asm"
	%INCLUDE "features/strings.asm"

; ==================================================================
; END OF KERNEL
; ==================================================================