From 351d6953909022e742957cde3276c00bef7b54a5 Mon Sep 17 00:00:00 2001
From: anurag-bit <singh.ask@outlook.com>
Date: Sat, 21 Oct 2023 00:55:26 +0530
Subject: [PATCH] implementing filesystem 2/3

---
 anurag-os-dev/build/bootloader.bin    | Bin 0 -> 512 bytes
 anurag-os-dev/build/main_floppy.img   | Bin 1474560 -> 1474560 bytes
 anurag-os-dev/src/bootloader/boot.asm |  94 ++++++++++++++++++++++++++
 3 files changed, 94 insertions(+)

diff --git a/anurag-os-dev/build/bootloader.bin b/anurag-os-dev/build/bootloader.bin
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..03774dab6452d89351311b2b9f776b86454e0cbe 100644
GIT binary patch
literal 512
zcmaEDF~K)D+|$oQ&yazMk&%Jv0fPhg2Tled1||js&=fKWt8nxS4RUl>@DFx#3^6oP
zcr6kZ5WI%tKncedzU>TW1zvxSj)*(FgMp#%M&E(H3ws!9_NCUmxb^?b>wg}pIXU?X
V<@rT9DT=&Y2xCWC0~`XOs{k~fC(r-@

literal 0
HcmV?d00001

diff --git a/anurag-os-dev/build/main_floppy.img b/anurag-os-dev/build/main_floppy.img
index 3999f4597e09cf5d175c8ac07b398bcad42fbf1d..de79e070cbf4d697f3d17c0ff3c702948cbe3c28 100644
GIT binary patch
delta 184
zcmXwuI|{-;07N(IH^yI#iiO33)}mrzC1fB<P$MM9Kzi?B87!t&PhjN*auknY;SIzO
zIK_MLCQ0HXiH*nfv<@QIn+!&0qiZ!LyMyh8zP(VJU~X?mV|77K+oye8we+Rc`$Lfl
zqc9TU>kmI$I=<(ul!EK2&aeM}DTGW-`7~1{@A?shMo1z<WQiP+CkjN7(1{XZ5M`o5
UREZi<CrqM2SVWU(-O!%B0bKJhZU6uP

delta 310
zcmZo@h-zqv;(l#2AvZg%ST8NHWFogry|IZ!h@X>xumS|QIffV-0hxUA`=V>sC><!_
z4%@=Fo1NjTK-}vOMo-R)ot1q3FC-(gSOJLg@=FvF6_WDvOA?cEQWa7%i?j6<6asQm
z6N^(7GV_X4i%{g#a`FobDisp*Qh2!vic*V<flTpAh3wQyg_3-Qk|Ll~dSYgtf}Wn9
z!p1^J#?Aj21yl^SmxhFggflRJXa+Fwb`A1#^-)l8^7K=X0E@%qnHU(DHVZPn7u>AC
zbeXfssm+P8&55baiMh>*rOk=8&55neiM`E<qs@u4&55hciM!2-r_G7C&55tgiNDQB
Ypv_6J%}J=uNx02Pq|HfmnUk0u0IL~dz5oCK

diff --git a/anurag-os-dev/src/bootloader/boot.asm b/anurag-os-dev/src/bootloader/boot.asm
index e69de29..89b3638 100644
--- a/anurag-os-dev/src/bootloader/boot.asm
+++ b/anurag-os-dev/src/bootloader/boot.asm
@@ -0,0 +1,94 @@
+org 0x7C00
+bits 16
+
+%define     ENDL   0x0D, 0x0A
+
+;
+;FAT12 header 
+;
+
+jmp short start
+nop 
+
+bdb_oem:                              db 'MSWIN4.1'             ; 8 bytes 
+bdb_bytes_per_sector:                 dw 512                    ;
+bdb_sectors_per_clusters:             db 1                      ;
+bdb_reserved_sectors:                 dw 1
+bdb_fat_count:                        db 2 
+bdb_dir_entries_count:                dw 0E0h
+bdb_total_sectors:                    dw 2880                   ; 2880*512 = 1.44megabytes
+bdb_media_descriptor_type:            db 0F0h                   ; f0 =m 3.5" floppy disk 
+bdb_sectors_per_fat:                  dw 9                      ; 9 sectos/fat 
+bdb_sectors_per_track:                dw 18 
+bdb_heads:                            dw 2
+bdb_hidden_sectors:                   dd 0
+bdb_large_sector_count:               dd 0 
+
+;extended Boot record 
+ebr_drive_number:                     db 0                      ; 0x00 floppy, 0x80 hdd, useless
+                                      db 0                      ; reserved
+ebr_signature:                        db 29h
+ebr_volume_id:                        db 12h, 34h, 56h, 78h     ; serial does not mean to our purpose.
+ebr_volume_label:                     db 'ANURAG OS'            ; 11 bytes, padded with space 
+ebr_system_id:                        db 'FAT12 '               ; 8 bytes                      
+
+
+start:
+    jmp main 
+
+;
+;
+;Prints a String to the screen.
+;Params:
+; - ds:si points to strings
+;
+;
+puts:
+    push si 
+    push ax 
+    push bx 
+
+.loop:
+    lodsb           ;loads the next character in al 
+    or al, al       ;verify if next character is null?
+    jz .done
+    
+
+    mov ah, 0x0E    ;call bios interrupt routine
+    mov bh, 0          
+    int 0x10
+
+    jmp .loop
+
+.done:
+    pop bx
+    pop ax
+    pop si
+    ret
+
+
+main:
+    ; setup data segments
+    mov ax, 0               ;can't write to ds/es directly 
+    mov ds, ax 
+    mov es, ax
+
+    ; setup stack 
+    mov ss, ax
+    mov sp, 0x7C00  ; stack grows downwards from where loaded into memory
+
+; print message 
+    mov si,  msg_hello
+    call puts  
+
+    hlt
+
+.halt:
+    jmp .halt
+
+
+msg_hello: db  'Hello world!', ENDL, 0
+
+
+times 510-($-$$) db 0
+dw 0AA55h