Other Ways to Initiate a System Boot

Turning on power to the computer is the most obvious, but not the only way of starting a boot sequence. The others are:

Software-initiated: Most operating systems have a way of restarting the system. These methods essentially consist of shutting down the running system and then simulating the power on sequence, i.e.
1. Setting the processor registers into a known specified state
2. Transferring control to either the BIOS or UEFI.
Pressing the Reset button: This generally disrupts the "power stable" signal from the power supply to the CPU. Thus, when this button is pressed, the CPU stops operating, and when the reset button is released, the CPU initiates a Power on Reset initiating a boot sequence.
System Failure: There are two types of system failure:
- A "crash" (aka "panic" in Linux or "Blue Screen of Death" (BSOD)--or more officially "System Stop"--in Windows.) These are initiated by the OS in response to the hardware or software detection of a failure of some kind. The OS will then either
  - stop, requiring the user to either press the reset button (described above) or cycle the power causing a power on reset
  - or cause a software-initiated restart (also described above).
- A "hang" (where the system simply stops responding or becomes unacceptably slow). This requires the user to either press the reset button (described above) or cycle the power causing a power on reset.