From 0d537e16046b8a4c899c6ccf21626b5dda5d3b34 Mon Sep 17 00:00:00 2001
From: Carlos Fenollosa <carlos.fenollosa@gmail.com>
Date: Mon, 29 Sep 2014 11:14:34 +0200
Subject: [PATCH] simple boot sector

---
 00-environment/README.md      |   5 ++++-
 01-boot-sector/.README.md.swp | Bin 12288 -> 0 bytes
 01-boot-sector/README.md      |  37 ++++++++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletion(-)
 delete mode 100644 01-boot-sector/.README.md.swp

diff --git a/00-environment/README.md b/00-environment/README.md
index 08cf531..fd85aaa 100644
--- a/00-environment/README.md
+++ b/00-environment/README.md
@@ -3,4 +3,7 @@ available for you.
 
 On a mac, [install Homebrew](http://brew.sh) and then `brew install qemu nasm`
 
-Don't use the Xcode developer tools `nasm` if you have them installed, they won't work for the most cases.
+Don't use the Xcode developer tools `nasm` if you have them installed, they won't work for the most cases. Always use `/usr/local/bin/nasm`
+
+Furthermore, on a mac, qemu is split into multiple binaries. You will want
+to call `qemu-system-x86_84 *binfile*`
diff --git a/01-boot-sector/.README.md.swp b/01-boot-sector/.README.md.swp
deleted file mode 100644
index dc243f91b5be1830b469d863de1a5fdc17cd4358..0000000000000000000000000000000000000000
GIT binary patch
literal 0
HcmV?d00001

literal 12288
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z{1LG6ukar*z{I<Yql8EmVJvzle|0+F`}w)a@&*3OvvYjx9RrQq0Pi0h4l&%@`FtNB
zjAgFVRF}eTUO%!xc&QFWdcBF;dAkbO85DXF=vil=!zz=xDLW%&k}BxvvTZ7(3nkKy
z-)#q4n|3KfdeeD++8>;sdRg?BJiN^Wn7{^s%Eav_yKsEe_3h5X=04uL`(ne0mrQ^O
zFaajO1egF5U;<2l3H;9l%%lPDsKK4O$vgGj*qG}jPfUObFaajO1egF5U;<2l2`~XB
zzyz4U4J07wXL@57K#=VJ|K<1p*INKzNQUH*zV88iB7G#iCN)X>q+jIslk|i1jr4&e
zNiN<E<iRB~0Vco%m;e)C0!)AjFaajO1XcumAGdsZy(>3hOM5cw^-zd^uy>I`KE*h~
zINq`_psE0di7JsElSnL8Hc4e^&|bI3#dT|xZ)9--(Cc<l<Pr9|N2p_GF49zvWb}u%
zC?p1RBTKyUXZ=3)?!i!FCdL%LqD_+s<Gh=ZD#tdnO(ud=He2rfv$Km!3=<iSZBb<G
z!U5Dto!6sqo~k^O1^O*aq=@WX*Xtj;Iu&K1q@^p^h45gKijeA6ISL%-dYY4yp{7I;
zp}o0ol+HaI+N8_n5>2cM;<88qk)+0jZF13#phk>#)vuAWk*adh)Y@yzDoa?xt3>9`
zC)C-bGSrN<svR7KNXs%mFs@ci^wcIvHFawb>*A8C*Qm_u4C$oiC}*KEDj&6QDh~+w
WNYlc4hJ~b>QC9_0>+7es55EB)!wo|K

diff --git a/01-boot-sector/README.md b/01-boot-sector/README.md
index 8b75e10..f641e35 100644
--- a/01-boot-sector/README.md
+++ b/01-boot-sector/README.md
@@ -1,5 +1,8 @@
 This is very exciting, we're going to create our own boot sector!
 
+Theory
+------
+
 When the computer boots, the BIOS doesn't know how to load the OS, so it
 delegates that task to the boot sector. Thus, the boot sector must be
 placed in a known, standard location. That location is the first sector
@@ -15,3 +18,37 @@ e9 fd ff 00 00 00 00 00 00 00 00 00 00 00 00 00
 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa
 ```
+
+It is basically all zeros, ending with the 16-bit value
+`0xAA55` (beware of indianness, x86 is little-endian). 
+The first three bytes perform an infinite jump
+
+Simplest boot sector ever
+-------------------------
+
+You can either write this with a binary editor, or just write a very
+simple assembler code:
+
+```
+; Infinite loop (e9 fd ff)
+loop:
+    jmp loop 
+
+; Fill with 510 zeros minus the size of the previous code
+times 510-($-$$) db 0
+; Magic number
+dw 0xaa55 
+```
+
+To compile:
+`nasm -f bin boot_sect_simple.asm -o boot_sect_simple.bin`
+
+> OSX warning: if this drops an error, read chapter 00 again
+
+I know you're anxious to try it out (I am!), so let's do it:
+
+`qemu boot_sect_simple.bin`
+
+You will see a window open which says "Booting from Hard Disk..." and
+nothing else. When was the last time you were so excited to see an infinite
+loop? ;-)