README

Quarta Bootmanager

Quarta is a boot manager for IBM PC computers. It is so tiny that it fits into the first sector of any harddisk, along with the partition table. I wrote quarta a long time ago because I was in need of a boot manager and because I was curious about low level programming. It is now only of historical interest, if it is at all interesting.

Technical Notes

In the IBM PC world, the first sector of a hard disk is known as the Master Boot Record or MBR for short. It contains at most 400 bytes of code followed by the partition table of about 100 bytes at the end of the sector. This table has four entries and each describes one partition of the disk: where it starts, where it ends, what type it is, etc.

When the computer is turned on, the BIOS loads the hard disk's first sector into memory and transfers control to the code contained in it. This code looks at the partition table and loads the first sector of the one partition that is marked as active into memory. This sector is known as the boot sector. It contains a small program that loads and launches the operating system. The quarta boot manager replaces the code in the MBR by a program that presents a simple user interface that allows the user to choose which of the (at most) four partitions to start.

Files

• Read the documentation: quarta.txt
• Download the installer: quarta.exe
• Browse the source code: quarta.asm and quarta.pas

Building

The source code consists of two modules, the boot manager written in assembler and the installation program, written mostly in Pascal with some assembler. Both modules are linked together to build the executable, quarta.exe. Here is the DOS batch file used to do that:

@echo off
echo This batch file builds the QUARTA boot manager
echo and installation program. The boot manager code
echo will actually be incorporated into the installer.
pause

tasm quarta.asm
tlink quarta.obj
exe2bin quarta.exe quarta.bin
binobj quarta.bin quarta.b2o partcode
bpc quarta.pas
del quarta.obj
del quarta.map
del quarta.bin
del quarta.b2o

echo.
echo Now you should have a newly built QUARTA.EXE; copy it
echo along with QUARTA.TXT to the distribution media.
echo.
echo QUARTA is copyright (c) 1995, 1996, 1997 by UJR

Above I used the Borland Pascal tools: tasm is the assembler, tlink the linker, exe2bin converts an exe file into a binary file, and binobj converts this binary file into an object code file, which is referred to from the Pascal source file using the {$L QUARTA.B2O} linker directive; finally, bpc compiles the Pascal source code and links it with the boot manager object code.

Notes

This README file was extracted from the 2004 quarta.html file.

The Master Boot Record (MBR) scheme was introduced by PC DOS in the early 1980ies. As of 2022 it is being (or mostly has been) superseded by a new scheme known as GUID Partition Table (GPT), which is part of UEFI, the successor of good-old BIOS.

License

This project is dedicated to the public domain, regardless of any copyright statements that may still be included in the files. The Unlicense (see file LICENSE) takes precedence!