Vgaromimage: file= $BXSHARE/VGABIOS-lgpl-latestįloppya: 1_44= "MyImg.img", status=inserted Romimage: file=$BXSHARE/BIOS-bochs-latest, address=0xf0000Ĭpu: count=1, ips=10000000, reset_on_triple_fault=1 Here is an example of an advanced configuration file: You can configure and build a whole PC, all you need to do is write the PC configuration to some text file (for example, bochsrc.txt) and place it in the Bochs folder. A more advanced look at BochsĪll this you can build with Bochs by only writing a simple configuration to a text file. Read the documentation that comes with Bochs and learn how to set break points ( lb 0x7c00), dump memory ( x /100bx 0x7c00), single stepping ( s 1), read registers ( r), continue execution ( c), dump all CPU registers ( dump_cpu) etc.įigure 3 – Bochs folder, and a simple configuration file.You can create floppies' images, hard disk images, and CD-ROM ( *.iso) images, and replace on them any Operating System you want (like WinXP etc.) and debug them.You can run your image with bochsdbg.exe for debugging.Now, run bochs.exe, and it would open two windows: a console window (for debugging) and a GUI window (this window simulates a screen of the emulated OS).Now, you need some kind of binaries to replace the image (you can take the BOOT.bin file from my first article and replace it in the first 512 bytes of the image you created.You can replace the file name MyOS.img with any file name you want (it must be the file that bximage.exe created (or any file of the right size)). Create a file name bochsrc.txt (this file is the initialization file for the emulator) and enter in this string: floppya: image="MyOS.img", status=inserted.Start bximage.exe and follow the instructions to create a virtual 1.44 MB (1,474,560 bytes) floppy disk image. Look for bochsdbg.exe (the emulator + debugger), and bochs.exe (emulator), and bximage.exe (disk image creator).Open the directory were you installed Bochs.Some people use it to run old computer games inside their non-compatible computers. Bochs can run on many host operating systems, including Windows, Linux, Mac OS X and the Xbox.īochs is mostly used for operating system development (when an emulated operating system crashes, it does not crash the host operating system, so the emulated OS can be debugged) and to run other guest operating systems inside already running host operating systems. Many guest operating systems can be run using the emulator, including DOS, several versions of Windows, BSDs, and Linux. It supports emulation of processor(s) (including protected mode), memory, disks, display, Ethernet, BIOS and common hardware peripherals of PCs. How to debug and test Operating Systems (the best and easiest way)įigure 2 – Bochs in work (Bochs is running my Boot sector from my other article).įor debugging and testing an OS you must have an x86 emulator, we would use Bochs.īochs is a portable open source x86 and AMD64 PCs emulator mostly written in C++ and distributed under the GNU Lesser General Public License. When resetting the drive with INT 13h, move the drive number to the register DL.Show you how to test and debug your Operating System in a very easy way.This article is the second part of my previous article. If you are not yet convinced, try it out and you would see how much fun it is to program Operating Systems. Learning all this would improve the programs you write a lot (even for regular Win32 user interface programming).Learning a lot of new tricks that can help you a lot in other kinds of programming.Learning the hardware of the Computer (CPU architecture, PCI, SATA, cash, Network card, ATA/ATAPI, etc.).Knowing what goes on behind the scenes.Learning the Assembler (Every one would admit, that knowing assembler is a wonderful thing).Learning the executables file format ( helps a lot).In the case of a programmer, the more he knows about the PC and the Operating system, his programs would be more reliable, stronger, and faster, and with less bugs. A programmer is like an astronaut in space, the more he knows about the spaceship he is flying, and how to fix it in case of a problem, it is more likely that he would return safely back to earth. Now, I would list what you will gain from learning how to develop an Operating System: It is not enough to read how an OS works, you have to build one with your own hands. I think that one of the most important ways of being a real professional programmer is to design and build an Operating System. Figure 1 - Running other Operating Systems in your current OS with a PC Emulator.
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