It can be done by calling the Mount command in the DOSBox prompt. But to access it in DOSBox, you’ll need to mount the folder where you saved it first. Now you have an executable that can be run and debugged in DOSBox. Select where to save the file and name it “hwex.exe”. In the menu, select “Run” and then “Compile”. Set data segment to same as code segmentĭb 'Hello World$' $ = end of string marker Once you have downloaded and installed the tools, start the Windows version of Flat Assembler and copy paste the code below in to the window. It gave a lot of insights into why Dune was programmed the way it was. (Contains references, but not a good place to start learning VGA programming I’m afraid.)Īlso a good read about Assembly programming is “ Zen of Assembly Language: Volume I, Knowledge” by Michael Abrash (Note: A volumn 2 was never published). FreeVGA - Graphics hardware information.- Contains information about the x86 architecture and more.DOS related FAQ on the Flat Assembler forum Various bits of information.

DOS INT 21h - DOS Function Codes More about talking to DOS.

Interrupt Services DOS/BIOS/EMS/Mouse For talking with DOS and the hardware.

Intel Pentium Instruction Set Reference All the instructions that can be used.

For anything they don’t cover, I’ll have to refer you to Google. It is far from complete coverage of everything worth knowing, but still helpful I hope. (Please note that Debug version of DOSBox requires that regular version is install.) InformationĪ few useful links. To begin with I’ll show you how to make an DOS executable with the Windows version and at the end, I’ll show how to use the DOS version. Both Windows and DOS versions of Flat Assembler exists. Toolsīeside debug version of DOSBox, I use the assembly compiler Flat Assembler. It is not the same as Assembler for DOS, but it will teach you the basic concepts. If you are completely new to Assembler, I suggest going through this guide for Linux Assembler. So for anyone else that wants to do the same journey, I have compiled some links and made a short Hello World example for an easier start. It was easy to find complete information on writing and build assembler code for Linux, but less so for good old MS DOS. I had some issues finding good information on how to get started with it though.

Simply to make sure that I understood the code and logic I was studying. When I started with reversing Dune I felt that I needed to code my own Assembler programs and run them DOSBox.

Dosbox built in debugger