xOS

A hobby Operating System made as a project

It was made in hopes of helping others get a base to write their own OS. It also exhibits how the low level programs interact with higher level C programs and how the booting process works. It also implements GUI and commands to show the implementation of VGA for graphics and other features.

Get Started

For those who want to simply run the project, just execute the build_and_run.sh script.

Prerequisites

grub-mkrescue -> To create ISO file
qemu-system-x86 -> To emulate the OS

Acknowledgements

Standard libraries courtesy of Pierre KRIEGER

References:

Multiboot Specification (Used in bootsector.asm)

: https://www.gnu.org/software/grub/manual/multiboot/multiboot.html

Read on VGA (helped in the cursor creation)

: http://www.brackeen.com/vga/

Read on the printf implementation

: http://www.sparetimelabs.com/tinyprintf/tinyprintf.php

multiboot.h

: https://www.gnu.org/software/grub/manual/multiboot/html_node/multiboot_002eh.html

General Guide

: http://www.osdever.net/

: https://wiki.osdev.org/

Interesting Notes:

How does bitmap work?

Each truetype font is represented in 8bits the first pixel being the MSB and the bottom right pixel is the LSB.

for example the character A is:

0x18 = | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 |

0x3C = | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 |

0x66 = | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 |

0x7E = | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 |

0x66 = | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 |

0x66 = | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 |

0x00 = | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

0x00 = | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

The position of 1s if filled with color makes the letter A

Check this link for more info: https://www.atbrask.dk/?p=182

A list of standard bitmap characters

//Based on Marcel Sondaar IBM (public domain VGA fonts)

char bitmap_letters[128][8] = {

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0000 (nul)

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0001

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0002

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0003

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0004

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0005

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0006

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0007

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0008

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0009

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000A

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000B

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000C

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000D

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000E

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000F

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0010

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0011

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0012

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0013

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0014

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0015

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0016

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0017

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0018

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0019

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001A

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001B

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001C

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001D

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001E

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001F

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0020 (space)

{ 0x18, 0x3C, 0x3C, 0x18, 0x18, 0x00, 0x18, 0x00}, // U+0021 (!)

{ 0x36, 0x36, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0022 (")

{ 0x36, 0x36, 0x7F, 0x36, 0x7F, 0x36, 0x36, 0x00}, // U+0023 (#)

{ 0x0C, 0x3E, 0x03, 0x1E, 0x30, 0x1F, 0x0C, 0x00}, // U+0024 ($)

{ 0x00, 0x63, 0x33, 0x18, 0x0C, 0x66, 0x63, 0x00}, // U+0025 (%)

{ 0x1C, 0x36, 0x1C, 0x6E, 0x3B, 0x33, 0x6E, 0x00}, // U+0026 (&)

{ 0x06, 0x06, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0027 (')

{ 0x18, 0x0C, 0x06, 0x06, 0x06, 0x0C, 0x18, 0x00}, // U+0028 (()

{ 0x06, 0x0C, 0x18, 0x18, 0x18, 0x0C, 0x06, 0x00}, // U+0029 ())

{ 0x00, 0x66, 0x3C, 0xFF, 0x3C, 0x66, 0x00, 0x00}, // U+002A (*)

{ 0x00, 0x0C, 0x0C, 0x3F, 0x0C, 0x0C, 0x00, 0x00}, // U+002B (+)

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x0C, 0x06}, // U+002C (,)

{ 0x00, 0x00, 0x00, 0x3F, 0x00, 0x00, 0x00, 0x00}, // U+002D (-)

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x0C, 0x00}, // U+002E (.)

{ 0x60, 0x30, 0x18, 0x0C, 0x06, 0x03, 0x01, 0x00}, // U+002F (/)

{ 0x3E, 0x63, 0x73, 0x7B, 0x6F, 0x67, 0x3E, 0x00}, // U+0030 (0)

{ 0x0C, 0x0E, 0x0C, 0x0C, 0x0C, 0x0C, 0x3F, 0x00}, // U+0031 (1)

{ 0x1E, 0x33, 0x30, 0x1C, 0x06, 0x33, 0x3F, 0x00}, // U+0032 (2)

{ 0x1E, 0x33, 0x30, 0x1C, 0x30, 0x33, 0x1E, 0x00}, // U+0033 (3)

{ 0x38, 0x3C, 0x36, 0x33, 0x7F, 0x30, 0x78, 0x00}, // U+0034 (4)

{ 0x3F, 0x03, 0x1F, 0x30, 0x30, 0x33, 0x1E, 0x00}, // U+0035 (5)

{ 0x1C, 0x06, 0x03, 0x1F, 0x33, 0x33, 0x1E, 0x00}, // U+0036 (6)

{ 0x3F, 0x33, 0x30, 0x18, 0x0C, 0x0C, 0x0C, 0x00}, // U+0037 (7)

{ 0x1E, 0x33, 0x33, 0x1E, 0x33, 0x33, 0x1E, 0x00}, // U+0038 (8)

{ 0x1E, 0x33, 0x33, 0x3E, 0x30, 0x18, 0x0E, 0x00}, // U+0039 (9)

{ 0x00, 0x0C, 0x0C, 0x00, 0x00, 0x0C, 0x0C, 0x00}, // U+003A (:)

{ 0x00, 0x0C, 0x0C, 0x00, 0x00, 0x0C, 0x0C, 0x06}, // U+003B (//)

{ 0x18, 0x0C, 0x06, 0x03, 0x06, 0x0C, 0x18, 0x00}, // U+003C (<)

{ 0x00, 0x00, 0x3F, 0x00, 0x00, 0x3F, 0x00, 0x00}, // U+003D (=)

{ 0x06, 0x0C, 0x18, 0x30, 0x18, 0x0C, 0x06, 0x00}, // U+003E (>)

{ 0x1E, 0x33, 0x30, 0x18, 0x0C, 0x00, 0x0C, 0x00}, // U+003F (?)

{ 0x3E, 0x63, 0x7B, 0x7B, 0x7B, 0x03, 0x1E, 0x00}, // U+0040 (@)

{ 0x0C, 0x1E, 0x33, 0x33, 0x3F, 0x33, 0x33, 0x00}, // U+0041 (A)

{ 0x3F, 0x66, 0x66, 0x3E, 0x66, 0x66, 0x3F, 0x00}, // U+0042 (B)

{ 0x3C, 0x66, 0x03, 0x03, 0x03, 0x66, 0x3C, 0x00}, // U+0043 (C)

{ 0x1F, 0x36, 0x66, 0x66, 0x66, 0x36, 0x1F, 0x00}, // U+0044 (D)

{ 0x7F, 0x46, 0x16, 0x1E, 0x16, 0x46, 0x7F, 0x00}, // U+0045 (E)

{ 0x7F, 0x46, 0x16, 0x1E, 0x16, 0x06, 0x0F, 0x00}, // U+0046 (F)

{ 0x3C, 0x66, 0x03, 0x03, 0x73, 0x66, 0x7C, 0x00}, // U+0047 (G)

{ 0x33, 0x33, 0x33, 0x3F, 0x33, 0x33, 0x33, 0x00}, // U+0048 (H)

{ 0x1E, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0049 (I)

{ 0x78, 0x30, 0x30, 0x30, 0x33, 0x33, 0x1E, 0x00}, // U+004A (J)

{ 0x67, 0x66, 0x36, 0x1E, 0x36, 0x66, 0x67, 0x00}, // U+004B (K)

{ 0x0F, 0x06, 0x06, 0x06, 0x46, 0x66, 0x7F, 0x00}, // U+004C (L)

{ 0x63, 0x77, 0x7F, 0x7F, 0x6B, 0x63, 0x63, 0x00}, // U+004D (M)

{ 0x63, 0x67, 0x6F, 0x7B, 0x73, 0x63, 0x63, 0x00}, // U+004E (N)

{ 0x1C, 0x36, 0x63, 0x63, 0x63, 0x36, 0x1C, 0x00}, // U+004F (O)

{ 0x3F, 0x66, 0x66, 0x3E, 0x06, 0x06, 0x0F, 0x00}, // U+0050 (P)

{ 0x1E, 0x33, 0x33, 0x33, 0x3B, 0x1E, 0x38, 0x00}, // U+0051 (Q)

{ 0x3F, 0x66, 0x66, 0x3E, 0x36, 0x66, 0x67, 0x00}, // U+0052 (R)

{ 0x1E, 0x33, 0x07, 0x0E, 0x38, 0x33, 0x1E, 0x00}, // U+0053 (S)

{ 0x3F, 0x2D, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0054 (T)

{ 0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x3F, 0x00}, // U+0055 (U)

{ 0x33, 0x33, 0x33, 0x33, 0x33, 0x1E, 0x0C, 0x00}, // U+0056 (V)

{ 0x63, 0x63, 0x63, 0x6B, 0x7F, 0x77, 0x63, 0x00}, // U+0057 (W)

{ 0x63, 0x63, 0x36, 0x1C, 0x1C, 0x36, 0x63, 0x00}, // U+0058 (X)

{ 0x33, 0x33, 0x33, 0x1E, 0x0C, 0x0C, 0x1E, 0x00}, // U+0059 (Y)

{ 0x7F, 0x63, 0x31, 0x18, 0x4C, 0x66, 0x7F, 0x00}, // U+005A (Z)

{ 0x1E, 0x06, 0x06, 0x06, 0x06, 0x06, 0x1E, 0x00}, // U+005B ([)

{ 0x03, 0x06, 0x0C, 0x18, 0x30, 0x60, 0x40, 0x00}, // U+005C (\)

{ 0x1E, 0x18, 0x18, 0x18, 0x18, 0x18, 0x1E, 0x00}, // U+005D (])

{ 0x08, 0x1C, 0x36, 0x63, 0x00, 0x00, 0x00, 0x00}, // U+005E (^)

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF}, // U+005F (_)

{ 0x0C, 0x0C, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0060 (`)

{ 0x00, 0x00, 0x1E, 0x30, 0x3E, 0x33, 0x6E, 0x00}, // U+0061 (a)

{ 0x07, 0x06, 0x06, 0x3E, 0x66, 0x66, 0x3B, 0x00}, // U+0062 (b)

{ 0x00, 0x00, 0x1E, 0x33, 0x03, 0x33, 0x1E, 0x00}, // U+0063 (c)

{ 0x38, 0x30, 0x30, 0x3e, 0x33, 0x33, 0x6E, 0x00}, // U+0064 (d)

{ 0x00, 0x00, 0x1E, 0x33, 0x3f, 0x03, 0x1E, 0x00}, // U+0065 (e)

{ 0x1C, 0x36, 0x06, 0x0f, 0x06, 0x06, 0x0F, 0x00}, // U+0066 (f)

{ 0x00, 0x00, 0x6E, 0x33, 0x33, 0x3E, 0x30, 0x1F}, // U+0067 (g)

{ 0x07, 0x06, 0x36, 0x6E, 0x66, 0x66, 0x67, 0x00}, // U+0068 (h)

{ 0x0C, 0x00, 0x0E, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0069 (i)

{ 0x30, 0x00, 0x30, 0x30, 0x30, 0x33, 0x33, 0x1E}, // U+006A (j)

{ 0x07, 0x06, 0x66, 0x36, 0x1E, 0x36, 0x67, 0x00}, // U+006B (k)

{ 0x0E, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+006C (l)

{ 0x00, 0x00, 0x33, 0x7F, 0x7F, 0x6B, 0x63, 0x00}, // U+006D (m)

{ 0x00, 0x00, 0x1F, 0x33, 0x33, 0x33, 0x33, 0x00}, // U+006E (n)

{ 0x00, 0x00, 0x1E, 0x33, 0x33, 0x33, 0x1E, 0x00}, // U+006F (o)

{ 0x00, 0x00, 0x3B, 0x66, 0x66, 0x3E, 0x06, 0x0F}, // U+0070 (p)

{ 0x00, 0x00, 0x6E, 0x33, 0x33, 0x3E, 0x30, 0x78}, // U+0071 (q)

{ 0x00, 0x00, 0x3B, 0x6E, 0x66, 0x06, 0x0F, 0x00}, // U+0072 (r)

{ 0x00, 0x00, 0x3E, 0x03, 0x1E, 0x30, 0x1F, 0x00}, // U+0073 (s)

{ 0x08, 0x0C, 0x3E, 0x0C, 0x0C, 0x2C, 0x18, 0x00}, // U+0074 (t)

{ 0x00, 0x00, 0x33, 0x33, 0x33, 0x33, 0x6E, 0x00}, // U+0075 (u)

{ 0x00, 0x00, 0x33, 0x33, 0x33, 0x1E, 0x0C, 0x00}, // U+0076 (v)

{ 0x00, 0x00, 0x63, 0x6B, 0x7F, 0x7F, 0x36, 0x00}, // U+0077 (w)

{ 0x00, 0x00, 0x63, 0x36, 0x1C, 0x36, 0x63, 0x00}, // U+0078 (x)

{ 0x00, 0x00, 0x33, 0x33, 0x33, 0x3E, 0x30, 0x1F}, // U+0079 (y)

{ 0x00, 0x00, 0x3F, 0x19, 0x0C, 0x26, 0x3F, 0x00}, // U+007A (z)

{ 0x38, 0x0C, 0x0C, 0x07, 0x0C, 0x0C, 0x38, 0x00}, // U+007B ({)

{ 0x18, 0x18, 0x18, 0x00, 0x18, 0x18, 0x18, 0x00}, // U+007C (|)

{ 0x07, 0x0C, 0x0C, 0x38, 0x0C, 0x0C, 0x07, 0x00}, // U+007D (})

{ 0x6E, 0x3B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+007E (~)

{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00} // U+007F

};