From the Wikipedia article: "Solipsism (from Latin solus, meaning "alone", and ipse, meaning "self") is the philosophical idea that only one's own mind is sure to exist. As an epistemological position, solipsism holds that knowledge of anything outside one's own mind is unsure; the external world and other minds cannot be known and might not exist outside of the mind. As a metaphysical position, solipsism goes further to the conclusion that the world and other minds do not exist."
The earliest known solipsist, according to the Wikipedia article, was the Greek philosopher Gorgias of Leontini.
The difference between the modern computer simulation version of solipsism and the traditional version of solipsism is that traditional solipsists were people interested in philosophy, who might be unkindly described as deep thinking losers, whereas the modern solipsist appears to have a high powered job in Silicon Valley or in banking.