Information Technology Reference
In-Depth Information
and so on. Work at this level emphasizes electrical activities and
detailed instructions to carry out basic operations. Applications,
such as word processors, spreadsheets, and Internet browsers,
represent highlevel virtual machines. As the topic progresses, we
will look at these various highlevel applications again. We also
will have occasion to explore some intermediatelevel virtual
machines.
Computers contain several primary components: the central
processing unit (CPU), main memory, and input/output (I/O)
devices. These are connected by wires, often called busses. Within a
computer, many circuits are combined into chips, and chips in turn
are placed on cards. You can see the cards and chips when you look
inside modern computers.
Latency measures the time required to accomplish a task,
such as the movement of data from one place to another.
Performance within computers can be improved in several ways,
such as:
Several pieces of data may move from place to place in parallel.
Small, highspeed memory (cache memory) may store fre
quently used information.
Processors other than the CPU may handle specialized pro
cessing tasks, informing the CPU through interrupts when the
tasks are done.
Information within computers can be divided into three general
categories: instructions, general data, and real (or floatingpoint)
numbers. CPUs are divided into pieces, each of which usually han
dles a specific type of information.
Although circuitry handles lowlevel tasks within a computer,
processing involves various levels of abstraction; work at high
levels can build upon tasks done at lower levels. The virtual
machine that users see, perhaps with windows and buttons for a
wordprocessing application, provides a functional environment
that builds on lowlevel operations that are available from more
primitive levels.
