Reset (computing)

A reset (English [ ɹi ː ' sεt ] to German: Reset ) is a process by which an electronic system is brought into a defined initial state. This may be necessary if the system is not working properly and does not respond to the usual inputs.

Regardless of this disaster situation automatically performs any electronic system that requires a defined initial state for its proper function, even at its normal start-up a reset.

Computer technology and other electronic systems

In execution of the Reset a PC, the entire PC, including the processors, controllers, and other functional units and assemblies contained therein takes to the intrinsic initial state. Therefore reset in German is often inaccurately referred to as a reboot.

For other electronic systems with spatially widely distributed components of the reset can also be limited to individual components, or within the components on individual functional units. Examples include control of industrial systems, electronic systems in motor vehicles, building management systems, computer networks, etc.

Reset Types of PCs

For a single PC, there are three types of reset:

• Warm start, Reboot, Restart
• Hardware reset
• Cold start

Warm start ( reboot)

The software-based system restart is a shortened boot procedure, triggered by keyboard input or commands.

Hardware reset

The hardware reset is initiated by pressing the reset button on the computer case. This works even if the operating system is no longer on input (usually the keyboard or mouse) responding. The reset button acts directly on the hardware and so bypasses the failed operating system.

On some newer PCs can be set in the BIOS, which event is to be triggered by pressing the reset button. This allows, for example, not crashed operating system will be informed that the reset button was pressed. The operating system can then take action and example shut down the machine clean, cached data permanently to the disk write, etc.

The reset button is usually located near the Einschaltknopfes. Many computers have these " emergency switch ", which allows you to reboot the PC when it " crashed" is. He is not on the keyboard. For some PC cases they can only be reached through a small hole into which one must introduce a thin, straight object ( such as a pen tip). Some laptops have to hold the power button to reset several seconds.

On many small computers (mobile devices ) such as MP3 players is the reset button as a tiny, recessed button usually on the back of the housing and can usually be operated only with a thin needle.

Older home computers like the C64 had no reset button. She was just as accessories from third-party suppliers (see image right).

Cold start

It may happen that a PC still does not respond to the reset button. Then, the power supply must be interrupted. This is also the power of all devices that are powered from the PC power is interrupted (eg, hard drives, and other drives with data therein carriers). Consequently, these devices may be affected. However, modern disks have a mechanism that makes it possible still to park the head and thus to prevent a head crash.

Problem of reset for PCs

Files and data that are not stored on the hard drive or other media, are after a reset as good as lost. Sometimes fragments of the old data can be found in the unoccupied memory of neugestarteten system.

As before resetting the operating system usually has not time, all its operations to end clean, a reset can have an inconsistency in the file system of impact. The operating system recognizes this but normally the next time, then checks the file systems and tries to repair them. Nevertheless, it can happen that data is lost on the hard drive if they are damaged by repairing the file system. In the worst case, it may happen that the entire file system of a partition is destroyed and lost all data on it or is recoverable only by data recovery.

Because the reset button on the front of the PC is easily accessible, it occurred in the past again and again to an unwanted pressing this button. As an antidote, the PC manufacturers have the buttons arranged recessed, hidden behind the small access holes and installed time delay for tripping. Some newer PCs, the reset button is even missing. Their function is then taken over by the power button to be pressed for several seconds.

Power On Reset ( POR)

As a Power On Reset is defined as the reset, which in non-trivial digital circuits (computers, embedded systems, ... ) provides for the application of the supply voltage for a defined start of the circuit once the supply voltages of the system have reached their nominal values. On a PC this is, for example, signaled by the power-good signal of the power supply. Embedded systems, either the microcontroller used has a built- POR circuit, or it is an external device used, such as a system basis chip or a fixed voltage regulator with reset output.

Other examples

On programmable calculators of the 1970s and 1980s had to be pressed to neutralize false charges after each battery change the reset button. This short has been regulated, for example, achieved in the Sharp "PC" using a button under the computer back, which could be forced through a small hole with a pen or the tip of a pencil. This also makes the memory of the computer was brought from an undefined state in a defined initial state.

Even with other electronically controlled devices may cause system crashes. In this case, it often helps as a last resort, a cold start using the power button or plug or by removing the battery or by pressing a certain " hard" reset combination. Possibly the power supply up to a minute to be interrupted long for the capacitors discharge. If this does not resolve the problem, usually there is a hardware error. For smaller devices, the memory is often powered by a backup battery so that a taking out the battery does not go through a short period of time to the destination.