Instant-on

In computers, instant-on is the ability to boot nearly instantly, thus allowing to go online or to use a specific application without waiting for a PC's traditional operating system to launch. Instant-on technology is today mostly used on laptops, netbooks, and nettops because the user can boot up one program, instead of waiting for the PC's operating system to boot. This allows a user to launch a single program, such as a movie-playing program or an internet browser, without the need of the whole operating system. There still remain a few true instant-on machines such as the Atari ST, as described in the Booting article. These machines had complete Operating Systems resident in ROM similar to the way in which the BIOS function is conventionally provided on current computer architectures. The "instant-on" concept as used here results from loading an OS, such as a legacy system DOS, with a small hard drive footprint. Latency inherent to mechanical drive performance can also be eliminated by using Live USB or Live SD flash memory to load systems at electronic speeds which are orders of magnitude faster.
Pros and cons.
An instant-on operating system is like those used by 1980s home computers such as the Commodore 64. This offers many advantages over a standard modern operating system:
However, this comes at the price of having limited local functionality, while focusing on web / cloud services. 
Consumer electronics.
In the past, consumer electronics manufacturers would emblazon radios and television sets with "Instant On" or "Instant Play" decals. In series filament sets, instant-on was accomplished by adding only a silicon diode across the power switch to keep tube filaments lit at 50% power; the diode was placed such that the typical half wave rectifier of the day was reverse-biased. Instant-on advantages included near-instant operation of the television or radio and potentially longer vacuum tube life; disadvantages included energy consumption and risk of fire. Most solid state consumer electronics are inherently instant-on, so the moniker survived into the early solid state era to differentiate a product from its vacuum-tube based brethren (with CRTs being a notable exception).