In
fact, they are universal information processing machines.
According to the Church-Turing thesis, a computer
with a certain minimum threshold capability is in
principle capable of performing the tasks of any other
computer, from those of a personal digital assistant
to a supercomputer, as long as time and memory capacity
are not considerations. Therefore, the same computer
designs have been adapted for tasks from processing
company payrolls to controlling unmanned spaceflights.
Modern electronic computers also have enormous speed
and capacity for information processing compared to
earlier designs, and they have become exponentially
more powerful over the years (a phenomenon known as
Moore's Law).
Computers are available in many physical forms. The
original computers were the size of a large room,
and such enormous computing facilities still exist
for specialized scientific computation — supercomputers
— and for the transaction processing requirements
of large companies, generally called mainframes. Smaller
computers for individual use, called personal computers,
and their portable equivalent, the laptop computer,
are ubiquitous information-processing and communication
tools and are perhaps what most non-experts think
of as "a computer". |
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