CompuServe (CompuServe Information Service, also known by its initialism CIS or later CSi) was an American online service, the first major commercial one in the world. It opened in 1969 as a timesharing and remote access service marketed to corporations. After a successful 1979 venture selling otherwise under-utilized after-hours time to Radio Shack customers, the system was opened to the public, roughly the same time as The Source. H&R Block bought the company in 1980 and began to more aggressively advertise the service. CompuServe dominated the industry during the 1980s and remained a major influence through the mid-1990s. At its maximum during the early 1990s, CIS was known for its online chat system, message forums for a variety of topics, extensive software libraries for most personal computers, and a series of popular online games, notably MegaWars III and Island of Kesmai. It was known also for its introduction of the GIF format for pictures and its system for exchanging GIF files. In 1994, it was described as "the oldest of the Big Three information services (the others are Prodigy and America Online)".In 1997, 17 years after H&R Block had acquired CIS, the parent company announced its desire to sell CIS. A complex deal was devised with WorldCom acting as a broker, resulting in CIS being sold to AOL. In 2015, Verizon acquired AOL, including its CompuServe division. In 2017, after Verizon completed its acquisition of Yahoo!, CompuServe became part of Verizon's newly formed subsidiary Oath Inc. At the time, the remaining original parts of CIS were closed down, leaving it as only as an internet service provider and a sub-brand of AOL. Oath was then divested as the new Yahoo! company during 2021. Source: Wikipedia (en)