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What is the origin of the power button? Is it supposed to resemble a physical switch?

Was it originally skeuomorphic UI design? Did it every move/turn or provide feedback?

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    it looks like you got plenty of toilet paper on the roll - ha
    – Jedi Commymullah
    Nov 11, 2015 at 2:54

5 Answers 5

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It's a stylised form of the '1' and the '0' for 'On' and 'Off'. You can see the evolution here.

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    Ha! I just posted the same thing but you beat me to it ;)
    – Roux Martin
    Jul 9, 2015 at 16:02
  • well, the more you knowI always thought they were meant to look like circuit icons (open / closed)
    – user3453281
    Jul 9, 2015 at 18:19
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    Note that according to this article the IEC designates the stylized 0/1 with the 1 half inside the "0" as a standby button, a full poweroff button has the 1 fully enclosed in the circle.
    – Johnny
    Jul 9, 2015 at 18:40
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    The article only claims to be conjecture about the 'evolution' of this symbol, and doesn't offer either references or a 'missing link' symbol which would make the theory plausible. The specific shape of the symbol seems unlikely if it had come from a combination of 0 and 1 - why is the 1 inside the 0? Why is the 0 not closed?
    – jwg
    Jul 9, 2015 at 21:34
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    I've often wondered if it is 0 & 1 (boolean) or "O" (open) and "|" (Closed) When seen on a rocker switch, I think open or closed circuit.
    – TecBrat
    Jul 10, 2015 at 10:41
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This symbol is comprised of a 1, indicating "on", and a 0, indicating "off".

enter image description here

It was originally designed to indicate "standby", or a low power state that was neither truly on or off. At that time, a 1 inside of a 0 was the power symbol.

enter image description here

On December 8, 2004, IEEE 1621 designated the former standby symbol as the new power symbol and designated a waning moon as the official "standby", or "sleep", symbol.

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    Can you identify where (which standard?) the IEEE did the designating?
    – Jonathan Leffler
    Jul 10, 2015 at 8:04
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    @JonathanLeffler IEEE 1621
    – Brian
    Jul 10, 2015 at 16:56
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While only conjecture and not supported by any evidence, this article makes a pretty good case for the evolution of the standby button: http://designblog.nzeldes.com/2008/05/the-evolution-of-the-onoff-power-switch-symbol/

The short version is that as rocker or toggle switches were replaced by momentary push-button switches the I / O symbols were merged to fit the single button interface.

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  • Which of the comments are you refering to?
    – Bergi
    Jul 10, 2015 at 6:08
  • @Bergi - I wasn't referring to any of the comments. Just the main article - It's the same one that Peter has linked to in his answer.
    – Roux Martin
    Jul 10, 2015 at 7:16
  • Ah, was just wondering, as designblog.nzeldes.com/2008/05/… would suffice :-)
    – Bergi
    Jul 10, 2015 at 7:22
  • It's not the letters I and O but the numbers 1 and 0.
    – David Richerby
    Jul 11, 2015 at 9:45
  • @DavidRicherby, I wasn't suggesting letters or numbers - I just used the characters that were closest to the symbols on the switches that may well mean 1 and 0 but the 1 never looks like a '1'. I am also not sure what this detail has to do with the validity of my answer.
    – Roux Martin
    Jul 12, 2015 at 13:03
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I must say the other answers are pretty convincing and they have a substantial basis in the references cited, but I believe there is another intepretation worth considering. Yet be advised: this is pure conjecture.

When you come to think about the word circuit, you will realize it resembles the word circle, and not only in English. A mechanical power button is, more or less, just a way of closing/opening the circuit. Power supply, capacitors are usually marked with perpendicular lines if I am not mistaken. I always posited that the button simply represents connecting/disconnecting of the circuit.

I write it only as an interesting (I hope) minority report, however, as I cannot provide any evidence that this is how it actually came to be.

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The statement I heard within IBM at the time was that this was a visual pun of sorts. Yes, the overlaid 1/0 idea was there, but the primary reference (it was claimed) was to the engineering schematic symbol for a particular kind of valve -- one in which the valve shaft rotates a disk to either block or permit flow through the pipe -- and thus was more directly intended to convey power on/off.

Take this with appropriate dose of skepticism, but i believe I have seen that use of this symbol.

The goal, of course, was to internationalize the machine, back in the days when human factor experts were rediscovering the idea of icons...and others were pointing out that icons weren't universal either, as demonstrated by the general dominance of alphabets over hieroglyphs. Whatever they did was going to generate complaints.

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  • Maybe we should go with alphabets instead of icons then?
    – user67695
    May 10, 2017 at 19:15

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