You missed calculators and there are rough catagories: First eletronic calc first pocket calc HP35 $700, the lowcost market breaker being the Bomar Brain. First programable calc <first personal computer (I think I know that one) If you mean PC (as in the IBM PC) then the answer is IBM. However if you man pc as in personally owned computer, then you go back by maybe 10-20 years to things like old surplus missle computers, homebrewed systems and PDP-8s and the like. Prior to the IBM abortion pc meant personally owned and was not based on what it was but who owned it. Personally owned computers was a new thing starting in the late 60s to early 70s. Around 72-73 it was possible to buy a used PDP-8 or CM2000 for a few thousand dollars. I know in December of 72 I almost bought a Cincinati Millicron CM2000 for the offered price of $2000(big bucks then) with 8k of core, serial line card and 6port muxed serial card. <first portable computer Define portable as I'd seen totables in the late 70s. One very nice one was an expanded EVK68 board in a classy wood case with a small crt and keyboard. One that comes to mind was the HP(5100?) complete packaged system with tape for storage and basic and GPIB for external interface. <first laptop Not sure but it wasnt a dos based for sure. Tandy trs100 or the similar NEC, Epson, and others. <first GUI Xerox PARC smalltalk <first OS This is real old likely in the late 40s early 50s and was likely a machine monitor system to load/save programs. Even the PDP-1 had an OS to timeshare multiple users. You may have to be more specific as to tthe type or style of OS as there are several and the appearance of each corosponds to emerging concepts in computing. Allison