Game demo
A game demo is a freely distributed piece of an upcoming or recently released video game. Demos are typically released by the game's publisher to help consumers get a feel of the game before deciding whether to buy the full version.
In the early 1990s, shareware distribution was a popular method of publishing games for smaller developers, including then-fledgling companies such as Apogee Software (now 3D Realms), Epic MegaGames (now Epic Games), and id Software. It gave consumers the chance to try a trial portion of the game, usually restricted to the game's complete first section or "episode", before purchasing the rest of the adventure. Racks of games on single 5 1⁄4" and later 3.5" floppy disks were common in many stores, often very cheaply. Since the shareware versions were essentially free, the cost needed only the covering of the disk and minimal packaging. Sometimes, the demo disks were packaged within the box of another game by the same company. As the increasing size of games in the mid-90s made them impractical to fit on floppies, and retail publishers and developers began to earnestly mimic the practice, shareware games were replaced by shorter demos that were either distributed free on CDs with gaming magazines or as free downloads over the Internet, in some cases becoming exclusive content for specific websites.
Shareware was also the distribution method of choice of early modern first-person shooters (FPS) like Wolfenstein 3D and Doom.
There is a technical difference between shareware and demos. Up to the early 1990s, shareware could easily be upgraded to the full version by adding the "other episodes" or full portion of the game; this would leave the existing shareware files intact. Demos are different in that they are "self-contained" programs which are not upgradable to the full version. A good example is the Descent shareware versus the Descent II demo; players were able to retain their saved games on the former but not the latter.
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