Pressing ctrl-alt-del wouldn't reset the machine. So that 32-bit supervisor did something else: it trapped ctrl-alt-del for itself. If you're running several DOS programs side by side, you don't want to reset the entire machine just because one of those programs is misbehaving. The utility of ctrl-alt-del to reset the computer still existed, of course, but the old BIOS-actuated set mechanism wasn't a good fit for this new multitasking environment. It always created one virtual machine to run Windows Standard Mode (within which 16-bit Windows applications were cooperatively multitasked), and each DOS program ran in its own, independent DOS virtual machine. Behind the scenes, Windows 3.0 Enhanced Mode was actually a lot more clever than people gave it credit for: it had a 32-bit supervisor that pre-emptively multitasked among a bunch of virtual machines. Second, Enhanced Mode Windows could be used to run multiple MS-DOS programs simultaneously. First, it could use virtual memory: it supported a pagefile and could move program memory between hard disk and RAM on an as-needed basis. Enhanced Mode Windows had two significant capabilities that Standard Mode Windows did not. It had "Standard Mode" for 286s and "Enhanced Mode" for 386s (and better). Microsoft wanted Windows to take advantage of the 386's extra hardware when possible, so Windows 3 had two distinct modes of operation. The 286 did have a limited protected mode of its own, but it lacked the richer capabilities of the 386. The 386 introduced lots of important on-chip hardware, such as support for virtually addressed protected memory and a special mode, "protected mode," to enable this hardware. Windows 3.0 lived in a world where 286s and 386s were both abundant. It became a prominent software feature with Windows 3.0's Enhanced Mode. Microsoft gets involved in the ctrl-alt-del actionīack in those early days, ctrl-alt-del was a BIOS feature. It became clear, however, that resetting the machine (to restart when a program hung, for example) was useful for end users, too, so it became one of the many things that early PC users had to learn and know about. The reset feature was originally intended to be an undocumented feature for IBM's own use. Ctrl-alt-del fixed that issue by using keys on both sides of the keyboard, it required the use of two hands. He originally planned to use ctrl-alt-esc, but he realized that ctrl-alt-esc might be dangerous, as you could press all three keys just by pressing down on the left-hand side of the keyboard. In 1980 or 1981-the exact date is lost to the mists of time, as it was " not a memorable event"-IBM engineer David Bradley coded a routine for the BIOS of the IBM PC to enable the machine to be quickly rebooted. It's a nice story, but it doesn't really add up.Ĭtrl-alt-del was invented by IBM in the early 1980s. After explaining the security rationale, Gates then said that it was a "mistake" and that it was due to IBM refusing to add a single button to take the place of the three finger salute. Speaking at Harvard earlier this month, Bill Gates was asked why you have to press ctrl-alt-del before you can enter your password and log in to Windows. We're republishing this piece from 2013, because we still think that Gates' telling of the story is a little misleading for IBM it was a feature, not a flaw, that ctrl-alt-del requires two hands, and if Microsoft really wanted a single button ctrl-alt-del for Windows NT, it was Microsoft, not IBM, with the market dominance to achieve that. Talking at Bloomberg Global Business Forum, Gates reiterates that he wishes IBM had created a dedicated button for the feature. Once again, Bill Gates has bemoaned the creation of the ctrl-alt-del shortcut.
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