DOSBox is an open source DOS emulator designed for running old games. Emscripten compiles C/C++ code to JavaScript. This is a version of DOSBox which can be compiled with Emscripten to run in a web browser. It allows running old DOS games and other DOS programs in a web browser.
DOSBox is distributed under the GNU General Public License. See the COPYING file for more information.
Currently, DOSBox compiles and runs various real-mode games successfully. DOSBox has not been fully re-structured for running in a web browser via the Emscripten main loop. Some programs can cause DOSBox to run a loop without returning control to the browser, causing DOSBox to appear to hang. The interactive DOS prompt cannot be used and leads to a hang. DOSBox can only run programs via command line arguments.
- Emscripten issues 1975 and 1992 were problems in the past. Use Emscripten 1.8.11 or later.
- Emscripten issue 1909 makes some switch statements highly inefficient. The main switch statements used for CPU emulation end up using long chains of comparisons, making DOSBox very slow. This problem does not have a proper fix. This patch is not totally correct, but it can be used and gives good performance in Firefox.
- V8 JavaScript Engine issue
2275 prevents large switch
statements from being optimized. Because of this and emscripten issue 1909,
the simple, normal and prefetch cores are automatically transformed. Case
statements for x86 instructions become functions, and an array of function
pointers is used instead of the switch statements. The
--enable-funarrayconfigure option controls this and defaults to yes. - The same origin policy prevents access to data files when running via a
file:// URL in Chrome. Use a web server such as
python -m SimpleHTTPServerinstead. - In Firefox, ensure that dom.max_script_run_time is set to a reasonable value that will allow you to regain control in case of a hang.
- Firefox may use huge amounts of memory when starting asm.js builds which have not been minified.
Configure with emconfigure ./configure and build with make.
This will create src/dosbox.js which contains DOSBox and src/dosbox.html,
a web page for use as a template by the packager. These cannot be used as-is.
You need to provide DOSBox with files to run and command line arguments for
running them.
Web pages for running DOS programs can be created using src/packager.py. If
you have an executable which needs no other files such as Gwbasic.exe, you
can package it via ./packager.py gwbasic Gwbasic.exe. That will create
gwbasic.html and gwbasic.data. Placing those in the same directory as
dosbox.js and viewing gwbasic.html will run the program. If you need to
package multiple files, place them in a directory, and package that directory,
specifying which executable to run. For examle, if Major Stryker is in
subdirectory major_stryker, package it using ./packager.py stryker major_stryker STRYKER.EXE. Again, place stryker.html and stryker.data in
the same directory as dosbox.js and view stryker.html to run the game.
Remember that the same origin policy prevents access to data files in some
browsers when using file:// URLs.
Most of the credit belongs to the DOSBox crew. They created DOSBox and made it compatible with a wide variety of DOS games. Ismail Khatib got DOSBox to compile with Emscripten, but didn't get it to work. Boris Gjenero started with that and got it to work. Then, Boris re-implemented Ismail's changes a cleaner way, fixed issues and improved performance to make many games usable in web browsers.