Appelman joined after his time at IBM, where he worked on some of the first standards to connect computers over the Internet (through what are known as Transmission Control Protocol/Internet Protocol or TCP/IP).
Before building a messaging program for the Internet, he created something else that would eventually spawn AIM.
"They didn't have any central presence information," Appelman said.
But AOL did have a manual way to search for said friends, if you knew their exact screennames.
Due to the way its system was constructed, AOL knew not just that people were logged on but which users they were.
This allowed for the construction of a location tool that proved extremely popular.
AOL had become a behemoth in the early days of the consumer Internet.
It handled around 180,000 simultaneous connections. Bosco said the goals for AOL's messenger were set much higher: 5 million simultaneous users.
"Buddy list was done without telling anybody, because we didn't have any product management then. People could suddenly spend as long as they liked online.