The operations of all digital computers are be carried
out by its use of the logic circuits. Logical circuits
are basically digital circuits whose single output
is determined by the conditions of the inputs that
are entered. The various circuits that are processing
the data must all work in a very synchronized manner.
The way that this is controlled is by the use of a
very stable oscillator. When digital computer circuits
operate at it's very high speeds, it is capable of
performing up to trillions of arithmetic or logical
operations per second! All of the information that
is processed is stored in the heart of the computer
also known as the CPU (Central Processing Unit).
Storage and Retrieval of Data:
In association with the CPU, is the storage unit,
or memory. Results or other data is stored for periods
of time ranging from a small fraction of a second
to many days or many weeks before being retrieved
for processing. Long ago computers used vacuum tubes,
but now computers have integrated circuits.
Auxiliary Storage:
Using an auxiliary storage can save programs and
data that are not being used by the main storage,
or some other form of external storage. Punch cards
once were used for storage, but now magnetic tape
and magnetic disks are used for storage can be read
and also written to. Also there are two types of Optical
disks, which can be used to store data as well, the
compact disk (CD) and its successor the Digital versatile
disk (DVD). The DVD is a more improved optical storage
technology that is capable of storing much more amounts
of data than can be stored on a CD. CD-Read-Only-Memory
(CD-ROM) and DVD-Read-Only-Memory (DVD-ROM) disks
can only be read, and cannot erase or re write new
information that is contained on the disk. In the
later part of the 1900's a new technology was invented.
The new technology was the creation of CD-Recordable
(CD-R) and DVD-Recordable (DVD-R). This technology
showed only one problem, there was no technology to
rewrite the information once it was placed on to the
disk, so of course the next thing to come along was
the CD-ReWritable (CD-RW) and the DVD-Random-Access-Memory
(DVD-RAM), which can be written to multiple times.
