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. o 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 these CD
disk are usually write ones and read many times (if the disk is not
multisession and re writable). So are the DVDs.
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