Memory and Storage Device || Computer's Memory || RAM || ROM || Secondary Storage Device || Difference between RAM and ROM
Memory and Storage Device:
The devices which are
used to store data and program in the computer is called storage or memory
devices. The storage or memory devices can be categorized in two types. They
are:
i)
Primary Memory
or Main Memory
ii)
Secondary Memory
or Storage Devices
i)
Primary Memory or Main Memory
The primary memory is also known as the
main memory or internal memory of the computer. It stores data and instructions
for processing while executing program. It communicates directly with the CPU.
The primary memory is fixed on the mother board inside the casing box. There
are two types of primary memory.
a)
Read Only Memory
(ROM)
b)
Random Access
Memory (RAM)
Read Only Memory (ROM)
ROM is a permanent
memory of the computer. It is called non-volatile memory. It provides startup
instructions when the computer is turned on. The instructions in ROM are stored
at the time of manufacturing of the computer. The instructions stored in ROM
cannot be changed by the user. Neither we can store data into the ROM. We can
only read data from it.
Random Access Memory (RAM)
RAM is the temporary
memory of the computer. The data stored in RAM are lost forever when the
computer is turned off so, RAM is also called volatile memory. This is the
memory where data and program instructions are stored while the computer is in
operation. So, it is considered as working memory of the computer. We can do
both read and write data into it.
Difference between RAM and ROM:
|
S.No
|
ROM
|
RAM
|
|
1
|
It stands for Read Only Memory
|
It stands for Random Access Memory
|
|
2
|
It is non volatile or permanent memory.
|
It is a volatile or temporary memory.
|
|
3
|
It is comparatively expensive.
|
It is comparatively cheaper.
|
|
4
|
It is startup memory of the computer which stores
the startup information.
|
It is working memory of computer which stores data
being currently processed.
|
ii)
Secondary Memory/Storage Device:
The secondary memory is also known as
storage devices. The data stored in secondary memory do not get erased when the
computer is turn off. When we store some data on the secondary storage devices
that remains there until you erase them. The commonly used secondary memory
devices are Hard disk, Floppy disk, DC-ROM, DVD-ROM, Pen drive, etc.
a)
Hard Disk:
Hard disk is the main and the largest
data storage device in the computer. It is also called the HDD (Hard Disk
Drive), hard drive or fixed disk. It can store a large amount of data
permanently. It is fixed inside the casing box and connected to mother board
with a data cable. The operating system software, other programs and most other
files are stored in the hard disk.
b)
Floppy Disk( Diskette)
Floppy disks also called floppies or
diskettes. It is a very popular magnetic storage disk of early days. It is a
light and portable secondary storage device. The floppy disk is used to
transfer small amount of data from one computer to another. A floppy disk is
needed to read data from floppy disk and write on it. Floppy disk are available
in different sizes and capacities. The most common size of floppy disk is 3.5”
in diameter and it has a storage capacity of 1.44 MB (Megabyte)
These days instead of floppy disks CDs,
DVDs and pen drives are used to store and transfer data. Compared to CDs and
DVDs, floppy disks can store only a small amount of data.
c)
CD-ROM
Compact Disk Read Only Memory is an
optical device which is the most popular and widely used storage. It uses laser
beams to read data from it and to write data into it. It has large storage
capacity than floppy disk. The normal CD-ROM can store up to 700 MB of data. We
can read data from it and also write data into it. A CD-ROM drive is required
to read data from it and to write data into it.
d)
DVD
DVD stands for Digital Versatile Disk or
Digital Video Disc. A DVD is also an optical disk but it has very high storage
capacity than CD-ROM. A DVD looks like CD but it is developed for a Compact Digital
Video format. Its storage capacity ranges from 4.7 GB to 200 GB. A single sided
DVD can normally storage upto 4.7 GB (Gigabytes) of data. DVD-ROM drive is
required to read data from it and to write data into it.
e)
Pen Drive:
Pen drive is also called flash drive, or
USB (Universal Serial Bus) drive or Thumb drive. It is small in size and can be
carried in a pocket like a pen so it is named as pen drive. It a very popular
and most widely used storage device today. It can be considered as a small external hard
disk. It storage capacity ranges from 128 Mb to a few GB (Gigabytes).