Although the series technically didn't include any RPGs, PC Gameworld has published
an article that details the history of Sierra's King Quest franchise and how PC gaming evolved after the first game's release. A snip:
Players would maneuver Sir Graham with the use of the arrow keys and would allow Graham to interact with the environment and other characters by typing in commands. This textual-input interface gave gamers a true challenge, as it required a quick and astute sense of thought on their part. Time was not always on your side so you had to enter your commands quickly and correctly. So, if you type slowly and your spelling sucks, then I suggest you do some brushing up before taking on this classic.
King's Quest III was by far my favorite!
Sierra Online and the Evolution of PC Gaming 
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