;This code was written specifically for the A86 assembler, although it may
;work with others such as TASM
.MODEL SMALL
.STACK 20H
.CODE

MAIN:
                                   
BOOTSEC: 
        THE_JUMP DB 0EBH, 3CH, 90H
        ;Jump to start of boot sector code
       
DOS_ID:         DB      "FD1", 0, 0, 0, 0, 0 ;Name of this boot sector (8 bytes)
SEC_SIZE: 	DW 	200H 		;Size of a sector, in bytes
SECS_PER_CLUST: DB      1               ;Number of sectors in a cluster
FAT_START:      DW      2               ;Starting sector for the first FAT
FAT_COUNT:      DB      2               ;Number of FATs on this disk
ROOT_ENTRIES:   DW      0               ;Number of root directory entries
SEC_COUNT:      DW      0B04H           ;Total number of sectors on this disk
DISK_ID:        DB      0F0H            ;Disk type code (This is 360KB)
SECS_PER_FAT:   DW      38               ;Number of sectors per FAT
SECS_PER_TRK:   DW      18              ;Sectors per track for this drive
HEADS: 		DW 	2 		;Number of heads (sides) on this drive
HIDDEN_SECS: 	DW 	0 		;Number of hidden sectors on the disk
DSKBASETBL:
		DB 	0 	;Specify byte 1
		DB 	0 	;Specify byte 2
		DB 	0 	;Wait time until motor turned off, in clk ticks
                DB      2       ;Bytes per sector (0=128, 1=256, 2=512, 3=1024)
		DB 	12H 	;Last sector number (lg enough to handle 1.44M)
		DB 	0 	;Gap length between sectors for r/w operations
		DB 	0 	;Data xfer lgth when sector lgth not specified
		DB 	0 	;Gap lgth between sectors for formatting
		DB 	0 	;Value stored in newly formatted sectors
		DB 	1 	;Head settle time, in milliseconds
		DB 	0 	;Motor startup time, in 1/8 seconds
HEAD: 		DB 	0 	;Current head to read from
					;Here is the start of the boot sector code
PRE_DNAME DB "Brian's Disk"
PRE_MESSAGE DB "Hello!!!"        ;Many boot disks use a jump to offset 62 for code

BOOT:                      ;so I am too.

        MOV AX, 7B0H
        MOV DS, AX
        MOV ES, AX

        JMP OVERDATA1
MESSAGE1 DB 13, 10, "Welcome to HCP OS 0.001!", 13, 10, 0
OVERDATA1:
        MOV BH, 0
        MOV SI, OFFSET MESSAGE1 ;[7C00H + 62 + 4]  ;[OFFSET MESSAGE1 + 7B00H]          ; + 7C00H - 100H
        MOV AH, 0EH
THELOOP:
        LODSB
        INT 10H
               
        CMP BYTE PTR [ES:SI], 0
        JZ TO_OS
        JMP THELOOP

TO_OS:
        MOV AH, 0
        MOV DL, 0
        INT 13H

        MOV BX, OFFSET BUFFER ;[7C00H + 512]   ;[OFFSET BUFFER + 7B00H]

;this code below loads 10 sectors (5120 bytes) from the floppy after the fat
;to mem at 7d0h
        MOV AH, 02H  ;byte offset = 77 * 512 = 39424
        MOV AL, 15   ;sector = int[(39424/512) + 1] mod 9 = 6 : CL = 6   
        MOV CH, 2    ;track = int[(39424/512) / 9] = 8        
        MOV CL, 6    ;head = track mod 2 = 8 mod 2 = 0        : DH = 0    
        MOV DX, 0    ;cylinder = fix(8 / 4) = 2               : CH = 2 & CL bits 7,6 = 0,0 
                     ;DX = 0  b/c  DL = 0 (floppy) & Head = 0
        INT 13H
        MOV AX, 7D0H
        MOV DS, AX
        MOV ES, AX
        JMP BUFFER

THE_STACK_SPACE DB 100 DUP (?)
STACK_POINTER:
                     ;Precompiled this was 153 bytes, need 512 so I added
                     ;this 357 byte dup & the boot signature bytes
SOME_SPACE DB 259 DUP (?)
SIGNATURE  DB 55H, 0AAH
BUFFER:
END MAIN