Electrical and Computer Engineering
History of Data Storage Devices
Types of Storage Devices
Data Storage Equipment
Various types of Energy used
Data: Smallest unit from which information or
data is derived.
Data Storage Devices : The devices used for
storing/recording any form of information are
called as data storage devices.
Issues to be considered
1) Energy Used.
2) Duration for which data is retained.
3) Volatile/Non-volatile devices.
4) Capacity to hold data.
HISTORY OF DATA STORAGE DEVICES
1940: Introduction of data storage devices
Punched card and Punched tape.
1951- 1st computer to use magnetic tape
1961-First hard disk was introduced
1962: laser diode led to development of Optical devices.
1963: removable disk storage
Floppy disk(1970-1971) , Compact Disk developed as a result of
Sony, Mitsubishi, Hitachi and Philips
1983- 1st Hard drive was introduced into market
1990- Array of inexpensive disks, flash cards.
1998- USB flash drive.
TYPES OF STORAGE DEVICES
Primary method of data storage
Hand, art, machine.
1975: Basile Bouchon used punched paper rolls to control
1846: Telegraphs could be prerecorded using punched tapes
and transmitted rapidly.
1880: Herman Hollerith invented the recording of data on a
medium that could then be read by a machine. Punched card
was being used after some time.
Advantage: Easy for human beings to produce copy of data.
Disadvantage: Cannot carry everywhere.
Storage of data on magnetic medium.
Magnetization techniques to store data.
Four ways to record data
1) Analog Recording
- Magnetization of a given material depends on the field
- Magnetic material is in the form of tape which is
demagnetized, the writing head magnetizes the tape with
current proportional to signal.
- Magnetization distribution is achieved.
- commonly used magnetic particles are Iron oxide particles
or Chromium oxide and metal particles with size of 0.5
micrometers. Eg: Magnetic tape sound recording.
2) Digital Recording
- records data in stepped pattern.
- binary data stored in sequence of 0s and 1s.
- it needs only two stable states for recording
+ve and –ve on the loop.
- polarity of the particles on the disk
determines if the value is positive or negative.
3) Magnetic Optical Recording.
- writes/reads optically.
- Writing: magnetic medium is heated by laser.
- Reading: Magneto-optical Kerr effect.
4) Domain Propagation Memory
- known as bubble memory
- refers to stable cylindrical domain.
- recording is done in presence or absence of
Electro-mechanical unit that can write or read on
a special disc medium using laser light.
Data stream is kept on the spiral path, data
begins at innermost track and works it towards
outer edge of disk.
Data stamped on the disk using machines in
Read by various devices using laser beam that
deflects off the disk.
Data can be stored for 5 to 10 years.
Prone to breakage and damage.
PRIMARY COMPUTER STORAGE
- Stored in random access memory (RAM). It is data from
currently running programs.
- Data lost when computer is turned off.
- Uses Hard drive
- retain data even if the power is turned off.
- Very Large Capacity.
- Data lasts from 5 to 10 years.
DATA STORAGE EQUIPMENT
1) PORTABLE METHOD
Easily to store and replace data.
a) Memory Card: used for storing digital information
- Data once stored can be deleted and replaced by new data.
- smaller in size, different capacities, retain data even if the
power is turned off.
Example: Micro SD cards.
b) Fabrication: act of making or constructing something from raw
material. Involves bending, cutting, assembling.
Wafer fabrication is procedure composed of many repeated
sequential process to produce complete circuits
Involves Textile fabrication, molding metals into assembly,
Automated Assembly etc.
PORTABLE METHODS CONT..
3) Disc Storage
- Recording of data using various electronic
mechanical, magnetic and optical methods on surface of
round rotating disc.
- Floppy disk drive and it removable floppy disk and
hard disk drives containing non-removable disc.
4) Flash Drive
- Universal serial bus integrated in it.
- Easy to connect, portable
- drives of 256 GB are available now
- It consist of small printed circuit board carrying the
circuit element and USB connector insulated electrically
and covered by plastic.
- Data lasts for 10 years.
SEMI PORTABLE METHOD
1) Hard Disk Drive:
- Computer component that writes data to and
retrieves data from hard disk.
- Non-volatile digital magnetic storage device.
- Used as secondary storage in computer, faster,
- Reads and writes data using electromagnetic
components known as heads. Heads connects to
sliders and sliders connect to arms. Actuators hold
the head, slider and arm in place over the surface
of hard disc that stores magnetic pattern . Hard
disk platters have holes at their centers and spin
around motor controlled spindles.
SEMI PORTABLE METHOD CONT.
2) Non- volatile RAM
It is a random access memory which retains its
information even if the power is turned off. It is
different than the normal Random Access
memories which require continuous power to hold
the data. It offers random access to the data.
Example is Flash Memory.
- Results in Loss of data if the power is
This kind of memory requires power to hold the
data. They easily lose data if power not connected.
They are also called as temporary memory. We use
word or any browser on computer, all works on
RAM. They are used as scratch pad for our
operations on data
VARIOUS TYPES OF ENERGY USED
Tape Storage – long, thin , flexible. Linearly moving bands
Disk Storage - flat, round, rotating object
Flash Memory and Memory Card- solid state semiconductor
1) Availability of more space: We get ample of
space to store data. Even if the primary hard
drive is full, we can transfer data to storage
2) Transfer of Files made easy : The easiest way
to transfer file from one computer to another is to
transfer it via a portable device.
3) Backups: We can always store data on storage
devices, and in case of loss of data, we can
retrieve data from the secondary storage.
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Q) What is double side polished wafer and is it more efficient
than single side polished wafer ?
The key advantage to using double side polished wafers
involves the improved flatness control. When the wafers
have removal from both sides simultaneously, the flatness
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This allows better critical dimension control for device
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Thank You !!