It is arguable which of the early microcomputers could be called a first. CTC Datapoint 2200
is one candidate, although it actually didn’t contain a microprocessor (being based on a
multi-chip CPU design instead), and wasn’t meant to be a standalone computer, but merely a
terminal for the mainframes. The reason some might consider it a first microcomputer is
because it could be used as a de-facto standalone computer, it was small enough, and its
multi-chip CPU architecture actually became a basis for the x86 architecture later used in
IBM PC and its descendants. Plus, it even came with a keyboard and a monitor, an exception
in those days.