The Altair 8800 made an Intel 8080 computer affordable enough for hobbyists to own, even though its original interface was little more than switches and lights on a front panel.
The Apple II kept the programmability and expansion of a hobby computer while packaging a keyboard, case, display support, color graphics, and ROM software as a product ordinary buyers could approach.
IBM built the 5150 quickly from commercially available parts and published enough technical detail for compatible hardware and software to flourish, turning one product into an industry standard larger than IBM itself.
Ted Nelson's Project Xanadu imagined a universal electronic literature built from two-way links, persistent versions, transclusion and attribution decades before the World Wide Web made simpler hypertext ubiquitous.
Alan Kay's Dynabook was not merely a prediction of the tablet. It was a proposal for a portable, programmable personal medium that children and adults could use to think, learn, create and communicate.
The Xerox Alto combined a bitmap display, mouse, Ethernet and interactive software into a personal networked workstation that became a laboratory for modern graphical computing.
Apple Lisa brought a mouse-driven graphical desktop into the personal-computer market while its designers repeatedly tested and revised icons, documents, menus and desktop behavior.
MS-DOS became the software layer underneath the IBM PC and its clones, helping turn one machine design into a vast compatible hardware-and-software ecosystem.
Smalltalk joined an object-oriented language, a graphical environment and a vision of personal computing into one unusually integrated system at Xerox PARC.