Transcript Computer memory: RAM

RAM
Random access memory, or RAM for short, is active
during the processing function. RAM is often referred to
as “temporary memory.”
RAM consists of electronic circuits on the motherboard
that temporarily hold programs and data while the
computer is on. Each circuit has an address that is used
by the microprocessor to transmit and store data. When
the computer is off, RAM is empty.
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RAM
RAM is constantly changing as long as the computer is on.
For example, if you are writing a paper, the word processing
program that you’re using is temporarily copied into RAM so
the microprocessor can quickly access the instructions that
you’ll need as you type and format your paper. The
characters you type are also stored in RAM, along with the
many fonts, special characters, graphics, and other objects
that you might use to enhance the paper.
A microcomputer with 128 MB of RAM can temporarily store
over 128 million characters at any one time. Many
microcomputers are said to be “expandable,” meaning that
additional RAM can be added to the computer.
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Virtual Memory
When you are multitasking, the processing memory
requirements can exceed the amount of available RAM.
If this occurs, today’s microcomputer software can
automatically use space on your computer’s storage
devices to simulate RAM. This extra memory is called
virtual memory.
Virtual memory is much slower than RAM, however.
Therefore, expanding the RAM capacity of a
microcomputer is preferable to using virtual memory.
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ROM
Read-only memory, or ROM, is a set of electronic circuits
permanently installed on the motherboard by the computer’s
manufacturer. ROM, sometimes called “permanent memory,”
is the permanent storage location for the instructions that
the computer uses when you turn it on. That is, when the
computer is turned on, the set of instructions in ROM checks
all the computer system’s components to make sure that
they are working and then activates the essential software
that controls the processing function. The activities 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.
Although a computer’s RAM capacity is typically expandable,
you cannot add to the ROM capacity.
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CMOS Memory
Complementary metal oxide semiconductor, or CMOS,
memory is also activated during the boot process. A small
rechargeable battery powers CMOS so that its contents will
be saved even when the computer is turned off.
CMOS memory is often referred to as “semipermanent
memory.” Unlike ROM, which cannot be changed, CMOS
must be changed every time you add hardware to or remove
hardware from your computer system. Most of today’s
computers have a “plug-and-play” feature that automatically
updates CMOS if you install new hardware such as a new
hard drive or printer.
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CMOS Memory
CMOS holds several critical computer configuration settings,
including those listed below.
• Date and time
• RAM capacity
• System performance parameters
• Power management settings
• Hardware passwords
• Configuration parameters for integrated peripherals
(storage drives, monitor, keyboard, mouse, printers, …)
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