In the latter half of the 1980s and into the early 1990s, the Quantum Link online service for Commodore 64 computers offered user-to-user messages between concurrently connected customers,  which they called «On-Line Messages» (or OLM for short), and later «FlashMail.»  (Quantum Link later became America Online  and made AOL Instant Messenger (AIM), discussed later). While the Quantum Link service ran on a Commodore 64 , using only the Commodore’s PETSCII text-graphics, the screen was visually divided into sections and OLMs would appear as a yellow bar saying «Message From:» and the name of the sender along with the message across the top of whatever the user was already doing, and presented a list of options for responding. As such, it could be considered a type of graphical user interface (GUI), albeit much more primitive than the later Unix , Windows and Macintosh based GUI IM software. OLMs were what Q-Link called «Plus Services»  meaning they charged an extra per-minute fee on top of the monthly Q-Link access costs.
Modern, Internet-wide, GUI-based messaging clients as they are known today, began to take off in the mid 1990s  with PowWow , ICQ , and AOL Instant Messenger . Similar functionality was offered by CU-SeeMe in 1992; though primarily an audio/video chat link, users could also send textual messages to each other. AOL later acquired Mirabilis , the authors of ICQ;  a few years later ICQ (now owned by AOL) was awarded two patents  for instant messaging by the U.S. patent office. Meanwhile, other companies developed their own software;  ( Excite , MSN , Ubique , and Yahoo ), each with its own proprietary protocol and client ;  users therefore had to run multiple client applications if they wished to use more than one of these networks.