Information Technology Reference
In-Depth Information
How are components connected within a computer?
As the addition example suggests, each component of a com
puter has circuitry to perform a specific task. Often this circuitry
is produced as a single electrical entity, called a chip . These indi
vidual components built from chips need to communicate on at
least two levels:
1. All components must be able to send signals or status reports
to the CPU and receive commands from it.
2. Data must be able to move between components.
Through this process, one can think of a signal or status
report to the CPU as being analogous to raising your hand in class
when you want to participate in a discussion or ask a question. In
the case of a keyboard, the signal or status report may indicate
that the user has typed something—perhaps after a long wait. For
a printer, the signal may indicate that the paper has moved to the
right place for actual printing to occur. Another type of signal or
status report might indicate that the printer is out of paper. The
details of signals or status reports can be tricky, but the idea is
fairly simple.
In practice, individual wires may be adequate to handle simple
status reports and CPU commands. However, to promote speed in
data communication, multiple wires are used. For example, several
characters may be sent from main memory to the CPU at once. For
convenience, both control wires and datacommunication wires
often are packaged together—sometimes in a configuration that
looks something like a ribbon (Figure 1.2a). Another common con
figuration involves several plug connections or slots, with parallel
wires connecting the respective connections of the various slots
(Figure 1.2b).
Another practical consideration is how to make the physical
connection between the parts of a computer. For example, initially,
one might consider connecting the CPU to main memory and to
each I/O device by a separate wire ribbon. However, even with only
a few such devices, the collection of such ribbons would become
 
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