The Windows 95 fast restart trick that hid complex engineering

Thirty years after its launch, Windows 95 continues to generate discussionBeyond the taskbar and the Start menu, this system hid a trick that many used without really knowing what was going on inside: a quick restart a secret that was activated simply by holding down the Shift key upon restarting.

Those who knew him saw the message appear «Please wait while Windows restarts"" or "Windows is restarting," and in a matter of seconds, the desktop would be operational again without going through the entire ritual of a complete shutdown and cold boot. For years it remained a somewhat mysterious anecdote, until veteran Microsoft engineer Raymond Chen explained it in detail. what was really happening in that process on his technical blog The Old New Thing.

The hidden fast restart of Windows 95

The trick was as simple to activate as it was poorly documented: It was enough to hold down the Shift key While selecting the restart option from the Start menu, instead of shutting down the entire system and restarting it, Windows executed an alternative path that displayed the message "Please wait while Windows restarts" and returned the user to the desktop much sooner than usual.

In the nineties, when mechanical hard drives were the norm and each reboot could take several minutes, this faster performance was a welcome help, especially in offices and homes in Europe where The machines coexisted with DOS applications and 16-bit softwareMany users believed it was a simple shortcut without much science, but in reality it hid a rather sophisticated internal sequence.

Raymond Chen explains that the key was in a special flag associated with the old ExitWindows functionThis was inherited from the 16-bit environment. When the system detected a restart using Shift, it did not order a complete computer restart, but rather a more limited operation: closing Windows and restarting it without resetting all the hardware.

With that shortcut enabled, Windows initiated a very specific sequence of steps. First, the 16-bit kernelthen it stopped 32-bit virtual memory manager Then the CPU would return to so-called "real mode," the most basic operating state of x86 processors. At that point, control would revert to the boot file. win.com with an internal signal that was equivalent to asking him: "Can you start Windows in protected mode again for me?"

From that point on, win.com took over and displayed the text "Windows is restarting", attempting to rebuild the environment as if the system It has just been launched from scratchbut without going through the entire standard power-off cycle.

What exactly was win.com doing during the fast restart?

The file win.com was a central piece of the startup of Windows 95. It was a .com program, written in assembly language, that was responsible for starting the graphical environment on top of DOS. In the context of a fast restart, its role was even more critical, because it had to simulate a clean boot from a system that, in reality, had not completely shut down.

According to Chen, once the CPU returned to real mode, win.com received a special instruction and proceeded to reset several global variables and command-line parameters to return them to their original values, as if the program were running for the first time. It was a complex internal "plumbing" job, precisely because everything was programmed in assembly language, without today's abstraction layers.

Files with the .com extension, such as win.com, were loaded by default, occupying all available conventional memoryHowever, in this specific case, the program freed almost all the remaining memory beyond its own image, aiming to leave a large contiguous block where Windows could be reloaded in protected mode. This maneuver was essential for the fast restart to function smoothly.

The problem arose when, during the session, another background program It used some of the memory that win.com had allocated. If software, a driver, or any utility occupied that space, conventional memory remained available. fragmented and the attempt to rebuild the original environment was no longer viable. In those cases, the quick reboot could not be completed as designed.

If the memory was clean and organized enough, win.com would jump directly to the code section responsible for Restart Windows in protected moderecreating the virtual machine manager and the 32-bit layers. The user would soon see the desktop and have the impression of having saved a good part of the process, which is exactly what happened.

An ingenious solution, but fragile and somewhat risky.

This entire mechanism allowed for shaving seconds or even minutes off startup time, but it didn't come without a price. Microsoft itself was aware that it was a workaround. ingenious but delicate, very typical of an era in which backward compatibility and extreme use of memory weighed more than elegance of design.

Chen recalls that the quick reboot wasn't intended as a fully secure, mass-use feature, but rather as a system capability. unofficially exploitedBy forgoing some of the usual startup checks, the system could be left in unpredictable states if something didn't restart as it should.

In particularly unfortunate situations, the win.com file could enter a reboot loop It was difficult to stop or leave the system in such an unstable condition that it would require a complete reinstallation of Windows 95. Some users reported crashes or errors after performing several consecutive quick restarts, probably because certain drivers did not return to a fully consistent state.

Another revealing detail of the era was the way memory was squeezed: parts of win.com's own code were they reused it as space for global variablesThe first bytes of the entry point, executed only once, were recycled to store data, under the assumption that this fragment would never be used again. In the context of a fast restart, the execution flow did not return to that point, so developers could get away with this kind of "trick" without apparent consequences.

From today's perspective it may seem like a reckless maneuver, but at the height of Windows 95 it was a pragmatic way of dealing with the limits of conventional memory and the necessary coexistence of 16-bit and 32-bit environments. It's not surprising that these internal routes weren't widely publicized to the general public.

From Windows 95 to today's fast startups

The philosophy behind this quick reset hasn't disappeared. In fact, a large part of Microsoft's current systems, such as Windows 10 or 11, They incorporate a quick start which, although not exactly the same, pursues a similar objective: avoid a full boot every time the user turns on the computer.

In modern versions of the system, the technique is different. Instead of relying on a program like win.com and the CPU's real mode, the kernel and main drivers are They are saved in a hibernation fileWhen you turn on the device, The system does not rebuild everything from scratch, but rather recovers that stored state., cutting out a good part of the initialization steps.

For the average user in Spain or any European country, this means that the computer goes from being off to working in a matter of seconds, something unthinkable when Windows 95 coexisted with slow hard drives and architectures riddled with compatibility patches. However, just like with the Shift key trick, It's not all advantages..

The modern quick start This can cause conflicts if certain controllers or external devices don't play well with that "halfway" state between shutdown and hibernation.; For example, Microsoft fixed a Windows 11 bug that prevented shutdownSome advanced users choose to disable the feature when they encounter stability problems, or force complete shutdowns when they need to apply critical system or hardware changes.

In any case, Raymond Chen's explanation of the Windows 95 fast restart helps to understand how certain ideas have endured over decades in the evolution of Windows. What in the nineties was done with ExitWindows flags, win.com and conventional memory, today is achieved with hibernation files and 64-bit kernels, but The goal remains the same: to reduce waiting times without excessively compromising stability.

That The old trick of holding down the Shift key while restarting perfectly sums up the Windows 95 era.A system designed based on a balance between compatibility, performance, and technical limitations, capable of hiding a reset mechanism under a simple interface. as fast as it is sophisticated and, at the same time, surprisingly fragile.

Related article:

How to tell if a Windows problem is caused by the BIOS without entering the BIOS

Alberto Navarro

I am a technology enthusiast who has turned his "geek" interests into a profession. I have spent more than 10 years of my life using cutting-edge technology and tinkering with all kinds of programs out of pure curiosity. Now I have specialized in computer technology and video games. This is because for more than 5 years I have been writing for various websites on technology and video games, creating articles that seek to give you the information you need in a language that is understandable to everyone.

If you have any questions, my knowledge ranges from everything related to the Windows operating system as well as Android for mobile phones. And my commitment is to you, I am always willing to spend a few minutes and help you resolve any questions you may have in this internet world.