Microsoft Office Tutorials and References
In Depth Information
in other words, RAM doesn’t need to access data in the same sequence in which it was
stored. For example, when you write a report, the microprocessor temporarily copies
the word processing program into RAM so the microprocessor can quickly access the
instructions you will need as you type and format your report. The characters you type
are also stored in RAM, along with the character formats, graphics, and other objects that
you might use. RAM is considered volatile memory or temporary memory because it
constantly changes while the computer is on and clears when the computer is turned off.
Most PCs use synchronous dynamic random access memory SDRAM ), which is (
chronized with the processor to allow faster access to its contents.
The computer advertised in the Visual Overview has 2 GB of RAM. In other words, it
can temporarily store over two billion characters at any one time. The notation “expand-
able to 8 GB” indicates that you can physically add more RAM to this computer.
Expandability is an important feature of any computer; you need to be able to change
your computer’s capabilities as your needs change.
Cache memory , sometimes called RAM cache or CPU cache , is a special, high-speed
memory chip on the motherboard or CPU. Because the computer can access cache
memory more quickly than RAM, frequently and recently accessed data and commands
are stored there instead of in RAM.
Virtual memory is space on the computer’s storage devices that simulates additional
RAM. It enables programs to run as if your computer had more RAM when all of the
available RAM is being used. It moves data and commands from RAM to the computer’s
permanent storage device to allow space for new data and commands. Figure 8 explains
how it works. Virtual memory is slower than RAM.
Figure 8
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 the
computer’s permanent
storage device (hard
disk drive).
Read-only memory ROM ) is a chip on the motherboard prerecorded with (
tions the computer uses to check its components to ensure they are working and to
activate the software that provides the basic functionality of the computer when you turn on
the computer. This set of instructions, called the BIOS (basic input/output system), tells
the computer to initialize the motherboard, how to recognize devices connected to the
computer, and to start the boot process. The boot process is the set of events that occurs
between the moment you turn on the computer and the moment you can begin to use
the computer. ROM never changes and it remains intact when the computer is turned
off; therefore, it is called nonvolatile memory or permanent memory .
Turning on the computer
is sometimes called
booting up.
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