How to run Windows 1.01 in your browser

Thanks to the surprising power and flexibility of JavaScript, you can now run Windows 1.01 in your web browser. Yes, despite missing the boat by some 28 years, you can now draw stunning monochrome art in the first version of MS Paint, take some notes in the original Notepad, or have your ass handed to you by Microsoft's shockingly good Reversi AI.

The browser-based version of Windows 1.01(Opens in a new window) is powered by PCjs, an IBM PC XT (Model 5160) emulator written in JavaScript. All major browsers support the emulator, including Safari on iOS and Chrome on Android. PCjs essentially emulates in software the entirety of the IBM PC ROM BIOS and MDA font ROM. The hardware of the emulated machine is highly configurable via XML -- in the case of the Windows 1.01 machine, PCjs emulates the Intel 8088 CPU at 4.77MHz, 256KB of RAM, and CGA graphics. Rather than emulating the specific hardware features of the IBM PC XT, it seems that PCjs is mainly interested in emulating all of the features in IBM PC BIOS that Windows 1.01 makes calls to.

For many of us, except the hardest and most veteran of PC users, Windows 3 and 3.11 were the first versions of Windows that enjoyed widespread use. Windows 1.01 was essentially a graphical interface, launched in 1985, that sat on top of MS-DOS. Windows 1.01 allowed you to multitask DOS applications through a rudimentary taskbar (which is surprisingly similar to the "pinned apps" paradigm of Windows Vista, 7, and 8).

Windows 1.01 was mostly notable for introducing the concept of device drivers, which allowed programs to easily invoke/interact with hardware (graphics cards, mice, printers, etc.) that previously could only be reached via the BIOS or bare metal. Windows 1 wasn't a massive success at the time, and neither was its contemporary, the Apple Lisa II.

Once you've poked around with the Windows 1.01 emulator (which won't take long), you might like to try out some other disk images that work with PCjs, such as Zork 1 for the IBM PC(Opens in a new window), or DONKEY.BAS(Opens in a new window), a very early DOS game co-written by Bill Gates. If Windows 1.01 is a little too, er, useless, you can also run Windows 3(Opens in a new window) and Mac OS System 7(Opens in a new window) in your browser using a JavaScript port of PCE (PC-Emulator).

While it might seem impressive, emulating some 30-year-old software and hardware in JavaScript is actually fairly simple. It's almost a perfect example of how Moore's law allows us to do things with computers today that are thousands or millions times more complex than in the 1980s. It isn't just about the raw power of modern-day hardware, either: JavaScript itself is going through something of a renaissance, with libraries such as asm.js allowing for JS performance that is tantalizingly close to native, compiled code.