Microsoft Office Tutorials and References
In Depth Information
Computer Hardware
Figure 15
How virtual memory works
3. The spreadsheet
program can now be
loaded into the RAM
vacated by the least-used
segment of the word
processing program.
1. Your computer is
running a word
processing program that
takes up most of the
program area in RAM,
but you want to run a
spreadsheet program at
the same time.
4. If the least-used
segment of the word
processing program is
later needed, it is
copied from virtual
memory back into
RAM. To make room,
some other infrequently
used segment of a
program will need to
be transferred into
virtual memory.
2. The operating
system moves the
least-used segment of
the word processing
program into virtual
memory on disk.
Read-only memory (ROM) is another set of electronic circuits on the motherboard
inside the computer. Although you can expand your RAM capacity, you cannot add to
ROM capacity. In fact, the manufacturer of the computer permanently installs ROM. It is
the permanent storage location for a set of instructions that the computer uses when you
turn it on. Because ROM never changes and it remains intact when the computer is
turned off, it is called nonvolatile .
The events that occur between the moment you turn on the computer and the moment
you can actually begin to use the computer are called the boot process , as shown in
Figure 16, and the act of turning on the computer is sometimes called booting up . When
the computer is off, RAM is empty. When the computer is turned on, the set of instruc-
tions in ROM checks all the computer system’s components to make sure they are work-
ing, and activates the essential software that controls the processing function.
 
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