Primary and Secondary Memory

[jayvrabara]

There are two types of
memories: Primary and
Secondary. The primary memory or the
main memory is part of the
main computer system. The
processor or the CPU directly
stores and retrieves
information from it. This memory is accessed by CPU,
in random fashion. That
means any location of this
memory can be accessed by
the CPU to either read
information from it, or to store information in it. The primary memory
itself is
implemented by two types of
memory technologies. The
first is called Random Access
Memory (RAM) and the other
is read only memory (ROM). A more appropriate name for
RAM is RWM (Read Write
Memory), the CPU can write
and read information from
any primary memory
location implemented using RAM. The other part of
primary memory is
implemented using ROM
which stands for Read Only
Memory. Primary memory is much
faster and also it is more cost
effective. But the secondary
memory is much slower and
also less costly. It stores the
data permanently unless it is erased. The secondary
memory is usually available
in the form of floppy disk
storage media, hard disk, CD,
DVD, Pen drive (i.e. Mass
storage devices), memory chips. A 5 and1/4 inch
floppy disk typically stores
1.44 mb of data. The data on
the floppy disk is organized
in terms of tracks and
sectors. Hard disk can have large capacity something like
80-300 GB's or higher. Hard
disk itself is made up of,
large number of platters.
Hard disk is usually much
faster compared to floppy disk. CD can store up to 750
mb of data. Information on
CD ROM is organized in terms
of a spiral track. A DVD is
digital Versatile Disk and can
store 4.6 Gigabyte of information. All theseCD disk
are usually write ones and
read many times (if the disk
is not multisession and re
writable). So are the DVDs.