where did the power button symbol come from
Power symbol The well-known on/off power symbol was the result of the logical evolution in user interface design. Originally, most early power controls consisted of switches that were toggled between two states demarcated by the words On and Off. As technology became more ubiquitous, these English words were replaced with the universal symbols line "|" and circle "o" (typically without serifs) to bypass language barriers. This standard is still used on toggle power switches.
Power good signal The Power Good signal (power-good) prevents a computer from attempting to operate on improper voltages and damaging itself by alerting it to improper power supply.