In the history of video games, the fourth generation of video game consoles, more commonly referred to as the 16-bit era, began on October 30, 1987, with the Japanese release of NEC Home Electronics' PC Engine (known as the TurboGrafx-16 in North America). Though NEC released the first console of this era, sales were mostly dominated by the rivalry between Sega and Nintendo across most markets: the Sega Mega Drive (Sega Genesis in North America) and the Super Nintendo Entertainment System (SNES; Super Famicom in Japan). Cartridge-based handheld consoles became prominent during this time, such as the Nintendo Game Boy (1989), Atari Lynx (1989), Sega Game Gear (1990) and TurboExpress (1990).
Nintendo was able to capitalize on its success in the previous, third generation, and managed to win the largest worldwide market share in the fourth generation as well. Sega, however, was extremely successful in this generation and began a new franchise, Sonic the Hedgehog, to compete with Nintendo's Super Mario series of games. Several other companies released consoles in this generation, but none of them were widely successful. Nevertheless, there were other companies that started to take notice of the maturing video game industry and begin making plans to release consoles of their own in the future. While as with prior generations, game media still continued to be primarily provided on ROM cartridges, though the first optical disk systems, such as the Philips CD-i, were released to limited success. As games became more complex, concerns over video game violence, namely in titles such as Mortal Kombat and Night Trap, led to the eventual creation of the Entertainment Software Rating Board.
The emergence of fifth generation video game consoles, circa 1994, did not significantly diminish the popularity of fourth generation consoles for a few years. In 1996, however, there was a major drop in sales of hardware from this generation and a dwindling number of software publishers supporting fourth generation systems, which together led to a drop in software sales in subsequent years.