RAM - random access memory
By Vangie Beal
RAM (
pronounced ramm) is an
acronym for
random access memory, a type of
computer memory that can be
accessed randomly; that is, any
byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in
computers and other
devices, such as
printers.
Main Types of RAM
There are two main types of RAM:
The two types of RAM differ in the technology they use to hold data,
with DRAM being the more common type. In terms of speed, SRAM is faster.
DRAM needs to be refreshed thousands of times per second while SRAM
does not need to be refreshed, which is what makes it faster than DRAM.
DRAM supports access times of about 60 nanoseconds, SRAM can give
access times as low as 10 nanoseconds. Despite SRAM being faster, it's
not as commonly used as DRAM because it's more expensive. Both types of
RAM are
volatile, meaning that they lose their contents when the power is turned off.
RAM, Main Memory and ROM Explained
In common usage, the term
RAM is synonymous with
main memory, the memory available to
programs. For example, a computer with 8MB RAM has approximately 8 million bytes of memory that programs can use. In contrast,
ROM (read-only memory) refers to special memory used to
store programs that
boot the computer and perform diagnostics. Most
personal computers have a small amount of ROM (a few thousand bytes). In fact, both types of memory (ROM and RAM) allow
random access. To be precise, therefore, RAM should be referred to as
read/write RAM and ROM as
read-only RAM.
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