Memory devices can be categorized as primary storage or secondary storage. Primary storage includes RAM and ROM. RAM is used to temporarily store data and programs being processed by the CPU. ROM permanently stores basic input/output programs like the BIOS. Secondary storage devices store data externally and include USB flash drives, external hard disks, optical disks like CDs/DVDs, memory cards, and online storage services. Common online storage services are DriveHQ, Dropbox, OpenDrive, SpideOak, and ZumoDrive.

1. Memory Devices

2. Definition-
In order for data to be processed by a computer,
they must first be stored in main computer
storage. Over the years, different memory
devices have been used to store data (as 1s and
0s) in main computer storage. In order to achieve
this memory devices were introduced.
Memory devices are of 2 types-
1. Primary storage
2.Secondary storage

3. 1. Random Access Memory (RAM)-
Primary storage
 Random Access Memory (RAM) is used when program
instructions or data are temporarily stored in the computer
before and after they are processed. RAM is also called primary
storage or main computer storage. RAM is very important to
computer systems. When the computer starts, the operating
system is loaded from storage into RAM, and when the user
opens an application software package, the instructions for it
are also loaded into RAM. As someone uses that software to
write a letter to his mother, for example, the characters he
types are held in RAM until he tells the software to perform
some action such as print the document. Having enough RAM is
important since it affects how quickly the user can perform
certain tasks. In some cases, the user will not be able to use
certain software programs if he does not have enough RAM.
 Random Access Memory can be static or dynamic . In static
random-access memory (SRAM), a small current is used to
maintain the stored data values without further manipulation
while the power is on.

4. 2. Read-Only Memory (ROM)-
 ROM, or read-only memory, is a type of semiconductor memory
that is permanent and cannot be erased. The Central Processing
Unit (CPU) can read data stored in ROM, but cannot write to
ROM. With ROM, the data are recorded when the memory is
manufactured. The data are activated when the computer is
turned on. ROM is normally used to store data and programs, such
as language interpreters (BASIC), display controllers, or the
storage of manufacturer-specific micro codes such as Basic Input
Output System (BIOS). Unlike RAM, ROM is not volatile.

5.  In the early 1950s, Jay W. Forrester
and his group at Massachusetts
Institute of Technology (MIT)
developed magnetic core storage,
which replaced vacuum tubes and was
the most popular device for storing
data in main computer storage for
two decades.
 Tiny donuts made of magnetic
material strung on wires into an
array: the idea revolutionized
computer memory. Each donut was a
bit, magnetized one way for “zero,”
and the other way for “one.” The
wires could both detect and change
the magnetization. In 1953, MIT’s
Whirlwind became the first computer
to use this technology.
3. Magnetic-core memory-
Jay W. Forrester

6.  Secondary memory (or secondary storage) is the slowest
and cheapest form of memory. It cannot be processed
directly by the CPU. It must first be copied into primary
storage (also known as RAM ).
 Secondary memory devices include magnetic disks like hard
drives and floppy disks ; optical disks such
as CDs and CDROMs ; and magnetic tapes, which were the
first forms of secondary memory.
Secondary memory-

7. 1. USB flash drive-
 A pen drive is a portable Universal Serial Bus (USB) flash
memory device for storing and transferring audio, video, and
data files from a computer. As long as the desktop or laptop
has a USB port, and the pen drive is compatible with the
operating system, it should be easy to move the data from
the hard drive to the device — and to another computer — in a
matter of minutes. The drive gets its name from the fact that
many have a retractable port connector like a ballpoint pen, and
they are small enough to fit into a pocket. Other names include
flash drive, jump drive, and thumb drive.

8. 2. External Hard disk-
 One major advantage of an external hard disk is you can send your
downloaded files directly to it which significantly reduces the
chance of a virus getting onto your main hard disk. Your computer
or laptop may be shared between family members or friends
meaning that you want to keep your private files private. With an
external hard disk you can take the files with you anywhere you
wish and lock them away.
 Most external hard disk disks are conveniently sized and you
simply plug them in via a USB port to start using them. They are
protected with a solid plastic case which also contains a fan to
keep the drive itself cool and regulate the temperature. You can
also get hold of external disks that use fire wire technology but
USB is much more common.

9. 3. Optical disks-
 Alternatively referred to as optical media and optical storage, an optical
disc drive (ODD) or optical disk is any storage media that holds content in
digital format and is read using a laser assembly is considered optical
media. The most common types of optical media are Blu-ray, CDs,
and DVDs. Computers can read and write to CDs and DVDs using a CD
Writer or DVD Writer drive, and a Blu-ray is read with a Blu-ray drive.
 There are three main types of optical media: CD, DVD, and Blu-ray disc.
CDs can store up to 700 megabytes (MB) of data and DVDs can store up to
8.4 GB of data. Blu-ray discs, which are the newest type of optical media,
can store up to 50 GB of data. This storage capacity is a clear advantage
over the floppy disk storage media (a magnetic media), which only has a
capacity of 1.44 MB. Another advantage that optical media have over the
floppy disk is that it can last up to 7 times longer, due to its improved
durability.

10. 4. Memory cards-
 A memory card or flash card is an electronic flash
memory data storage device used for storing digital
information. They are commonly used in many
electronic devices, including digital cameras, mobile
phones , laptop computers, MP3 players and video
game consoles. Most of these can be diminutive, re-
recordable, and can retain data without power

11. Online storage services-
 They usually use a virtual drive that exists on your
desktop in some manner, and it is linked directly to your
online storage space. The contents of this virtual hard
drive remain in sync across all of the desktops,
notebooks and mobile devices on which you have
installed the client software.
 You designate which files or folders that you want to be
part of the virtual drive; everything on that drive is
then automatically uploaded to an online server. From
there it is accessible (by logging on with a username and
a password) from your other devices, either from
another installed version of the application, or via a web
interface. And you can grant other people access.

12. Some common online memory
storage devices-
 DriveHQ File Manager
 Dropbox
 OpenDrive
 SpideOak
 ZumoDrive

13. Thank You
Efforts By-
Satyam Sharma
XI-F
Batch -2014-2015