Charles Babbage Invented the First Computer.
More Info: Technically speaking, the man who deserves credit for being the very first to imagine and diagram the power of a personal or desktop computer is British banker's son Charles Babbage (1791-1871). His Difference and Analytical Engines were the astonishingly forward-thinking progenitors of the modern computer, and for this achievement, Babbage was inducted into the inaugural class of San Diego's Computer Hall of Fame.
Our Computer Forefathers
However, in the same way that various interconnected components make up a personal computer motherboard, tracing the origins of the desktop computer lead to not just one individual but rather a daisy chain of trailblazers. First comes Seymour Cray, creator of the original supercomputer in 1958. Then there's Douglas Englebart, who designed the world's first computer mouse in the 1960's and then had to wait about a decade and a half until the rest of the computer invention world caught up to his tool.
Today's Computer Inventor
However, if you had to pick just one daisy chain inventor upon whom to heap the most credit for today's ubiquitous desktop computers, it would be M.E. "Ted" Hoff. As an employee of Intel in the early 1970's, he was tasked with creating a microprocessor chip to be used in calculators. He eventually created one the size of a pencil eraser and thanks to his invention, supercomputers and medium-sized units were able to give way to smaller personal computers that could be marketed. Today, Intel's ever-evolving generations of computer microprocessor chips anchor 80% of the world's computers (Desktop and laptop) and the company has become more profitable than the top ten PC makers combined.
One of the earliest desktop computers on the U.S. consumer market was introduced in 1975 by Altair. In the spirit of IKEA furniture, it came as an 8800 computer kit that required relatively extensive assembly. A few years later, Apple introduced its Apple II computer and in 1981, International Business Machines (IBM) stepped into the desktop computer market.