Since the
introduction of portable computers during the late 1970s, their form has
changed significantly, spawning a variety of visually and technologically
differing subclasses. Except where there is a distinct legal trademark around a
term (notably, Ultrabook), there are rarely hard distinctions between these
classes and their usage has varied over time and between different sources.
Since the late 2010s, the use of more specific terms has become less common,
with sizes distinguished largely by the size of the screen.
There were
in the past a number of marketing categories for smaller and larger laptop
computers; these included "subnotebook" models, low cost
"netbooks", and "ultra-mobile PCs" where the size class
overlapped with devices like smartphone and handheld tablets, and "Desktop
replacement" laptops for machines notably larger and heavier than typical
to operate more powerful processors or graphics hardware.[29] All of these
terms have fallen out of favor as the size of mainstream laptops has gone down
and their capabilities have gone up; except for niche models, laptop sizes tend
to be distinguished by the size of the screen, and for more powerful models, by
any specialized purpose the machine is intended for, such as a "gaming
laptop" or a "mobile workstation" for professional use.