RAM is a fast temporary type of memory in
which programs, applications and data are stored.
Here are some examples of
what's stored in RAM:
the operating system
the graphical user interface (GUI)
RAM: Random Access Memory
Rom is memory that cannot be changed by
a program or user. Rom retains its memory
even after the computer is turned off.
For example, ROM stores the instructions for the
computer to start up when it is turned on again.
ROM: Read Only Memory
SRAM is a type of RAM and it is a volatile memory, which looses
its data when the power is turned off. In a SRAM, each bit that
stores data is made up of four or six transistors that make up a
flip-flop. There are additional transistors that are used to control
read and write accesses of storage cells. Even though typical
SRAMs use six transistors to store each bit, there are SRAMs that
use eight, ten or more transistors to store a single bit.
When the number of transistors is reduced, the size of the
memory cell decreases. Each SRAM cell can be in three different
states called read, write and standby. A cell is in the reading state
when data has been requested and it is in writing state when the
data in the cell is modified. The cell is in the standby state when it
DRAM is also a volatile memory that uses separate capacitors to store
each bit. Capacitors when not charged represent the value 0 of a bit
and when charged represent the value 1. Since the capacitors discharge
with time, they need to be refreshed periodically to maintain the values
stored in them. Each memory cell in a DRAM consists of a capacitor
and a transistor and these cells are arranged in a square array. DRAMS
are widely used for main memories in personal computers and game
stations since they are cheaper.
DRAMs are manufactured as integrated circuits (ICs) that come in plastic packages with metal pins that could be
connected in to busses. Currently there are DRAMs in the market that are manufactured as plug-in modules, which
are easier to handle. Single In-line Pin Package (SIPP), Single In-line Memory Module (SIMM) and Dual In-line Memory
Module (DIMM) are some examples of such modules.