JULY 2008 | voL. 51 | no. 7 | COMMUNICATIONS OF THE ACM 9
T
HE GREEk MYTHS tell of crea-
tures plucked from the sur-
face of the Earth and en-
shrined as constellations
in the night sky. Something
similar is happening today in the world
of computing. Data and programs are
being swept up from desktop PCs and
corporate server rooms and installed
in “the compute cloud.”
Whether it’s called cloud comput-
ing or on-demand computing, software
as a service, or the Internet as platform,
the common element is a shift in the
geography of computation. When you
create a spreadsheet with the Google
Docs service, major components of the
software reside on unseen computers,
whereabouts unknown, possibly scat-
tered across continents.
The shift from locally installed pro-
grams to cloud computing is just get-
ting under way in earnest. Shrink-wrap
software still dominates the market
and is not about to disappear, but the
focus of innovation indeed seems to be
ascending into the clouds. Some sub-
stantial fraction of computing activity
is migrating away from the desktop and
the corporate server room. The change
will affect all levels of the computa-
tional ecosystem, from casual user to
software developer, IT manager, even
hardware manufacturer.
In a sense, what we’re seeing now
is the second coming of cloud com-
puting. Almost 50 years ago a similar
transformation came with the creation
of service bureaus and time-sharing
systems that provided access to com-
puting machinery for users who lacked
a mainframe in a glass-walled room
down the hall. A typical time-sharing
service had a hub-and-spoke configu-
ration. Individual users at terminals
communicated over telephone lines
with a central site where all the com-
puting was done.
When personal computers arrived
in the 1980s, part of their appeal was
the promise of “liberating” programs
and data from the central computing
center. (Ted Nelson, the prophet of hy-
pertext, published a book titled Com-
puter Lib/Dream Machines in 1974.) In-
dividuals were free to control their own
computing environment, choosing
software to suit their needs and cus-
tomizing systems to their tastes.
But PCs in isolation had an obvious
weakness: In many cases the sneaker-
net was the primary means of collabo-
ration and sharing. The client-server
model introduced in the 1980s offered
a central repository for shared data
while personal computers and work-
stations replaced terminals, allowing
individuals to run programs locally.
In the current trend, the locus of
Technology DOI: 10.1145/1364782.1364786 Brian Hayes
Cloud Computing
As software migrates from local PCs to distant Internet servers,
users and developers alike go along for the ride.
PHOTOGRAPH BY RICHARD MORGENSTEIN
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