By:Keval Patel(07)

Sandip Dobariya(13)

A data recorder device is a devicefor recording information.

Electronic data storage requires electricalpower to store and retrieve that data.

Electromagnetic data may be stored in eitheran analog or digital format on a variety ofmedia.

Floppy Disk

CD(Compact Disk)

DVD(Digital versatile disk)

Hard Disk

USB flash drive

RAM(Random Accsess Memory)

ROM(Read Only Memory)

Other recorders

The most common form of external storage device

used in a personal computer is a 3.5” & 5.5’’

FLOPPY DISK.

A high density floppy disk can hold up to 1.4

megabytes of data.

But some recent floppy disk can store up to

250MB of data.

It can be read or write by using floppy drive.

To protect the

magnetised, plastic

disk on which the data

is stored, a floppy disk

has a hard plastic

case.

A sliding metal cover

protects the

magnetised, plastic

disk when it is not in

the floppy disk drive.

Floppy Disk

A spindle motor in the drive rotates themagnetic medium at a certain speed, whilea stepper motor-operated mechanismmoves the magnetic read/write head(s)along the surface of the disk. Both read andwrite operations require the media to berotating and the head to contact the diskmedia, an action accomplished by a "diskload" solenoid.

FloppyDiskDrive

To write data, current is sent through a coil inthe head as the media rotates. The head'smagnetic field aligns the magnetic particlesdirectly below the head on the media.

To read data, the magnetic particles in themedia induce a tiny voltage in the head coil asthey pass under it. This small signal isamplified and sent to the floppy disk controller,which converts the streams of pulses from themedia into data, checks it for errors, and sendsit to the host computer system.

How therecorded datalooks like?

Media type Optical disc

Encoding Various

Capacity Typically up to 700 MB (up to 80 minutes audio)

Read mechanism 780 nm wavelength (infrared and red edge) semiconductor laser, 1200 Kb/s (1×)

Write mechanism 1200 Kb/s (1×)

Developed by Philips, Sony

Usage Audio and data storage

The Compact Disc, or CD for short, is an opticaldisc used to store digital data.

Standard CDs have a diameter of 120 millimeters(4.7 in) and can hold up to 80 minutes ofuncompressed audio or 700 MB (700 × 106 bytes)of data. The Mini CD has various diameters rangingfrom 60 to 80 millimeters (2.4 to 3.1 in); they aresometimes used for CD singles, storing up to 24minutes of audio or delivering device drivers.

A CD is made from 1.2 millimeters (0.047 in)thick, polycarbonate plastic and weighs 15–20 grams.

CD

CD-ROM CD-R CD-RW

This is the most common type of CD available,

and is the way in which most modern software is

supplied to individual personal computers.

It is a memory storage device but because it can

not be ‘written to’ it can not be regarded as a

‘backing store’.

These are supplied ‘blank’ and can be ‘written to’

by CD Writer drives.

They can be used to store large amounts of data,

but once used, they can not be re-used.

These are supplied ‘blank’ and can be ‘written to’

by CD Writer drives.

They can be used to store large amounts of data,

and can be ‘written to’ many times, just like a hard

disk.

CD data is stored as a series of tinyindentations known as "pits", encoded in aspiral track moulded into the top of thepolycarbonate layer. The areas between pitsare known as "lands". Each pit isapproximately 100 nm deep by 500 nm wide,and varies from 850 nm to 3.5 µm in length.The distance between the tracks, the pitch, is1.6 µm

A CD is read by focusing a780 nm wavelength (nearinfrared) semiconductor laser through thebottom of the polycarbonate layer. Thechange in height between pits and landsresults in a difference in the way the light isreflected. By measuring the intensity changewith a photodiode, the data can be read fromthe disc.

1 0

Media type Optical disc

Capacity 4.7 GB (single-sided, single-layer – common)8.5–8.7 GB (single-sided, double-layer)9.4 GB (double-sided, single-layer)17.08 GB (double-sided, double-layer – rare)

Read mechanism 650 nm laser, 10.5 Mbit/s (1×)

Write mechanism 10.5 Mbit/s (1×)

Standard DVD Forum's DVD Books and DVD+RW Alliance specifications

The DVD is now beginning to replace the CD as the main method of bulk saving data on personal computers.

The reason for this is that they are capable of storing much larger amounts of data.

A DVD can store 17 gigabytes of data

This is equal to 26 CD-ROMs or 12,000 floppy disks!

DVD uses 650 nm wavelength laser diode light as opposed to 780 nm for CD. This permits a smaller pit to be etched on the media surface compared to CDs (0.74 µm for DVD versus 1.5 µm for CD), allowing in part for DVD's increased storage capacity.

In comparison, Blu-ray Disc, the successor to the DVD format, uses a wavelength of 405 nm, and one dual-layer disc has a 50 GB storage capacity.

Drive speedData rate ~Write time (minutes)

Mbit/s MB/s Single-Layer Dual-Layer

1× 11.08 1.39 57 103

2× 22.16 2.77 28 51

2.4× 26.59 3.32 24 43

2.6× 28.81 3.60 22 40

4× 44.32 5.54 14 26

6× 66.48 8.31 9 17

8× 88.64 11.08 7 13

10× 110.80 13.85 6 10

12× 132.96 16.62 5 9

16× 177.28 22.16 4 6

18× 199.44 24.93 3 6

20× 221.60 27.70 3 5

22× 243.76 30.47 3 5

24× 265.92 33.24 2 4

In DVD the data can be recorded & can be read same as on CD.

Path of recording data On DVD.

Data tracks

Date invented 24 December 1954

Invented by IBM team led by Rey Johnson

A hard disk drive (HDD; also hard drive, harddisk, or disk drive) is a device for storing andretrieving digital information, primarilycomputer data. It consists of one or morerigid (hence "hard") rapidly rotating discscoated with magnetic material, and withmagnetic heads arranged to write data to thesurfaces and read it from them.

A typical HDD designconsists ofa spindle that holds flatcircular disks, alsocalled platters, whichhold the recorded data.The platters are madefrom a non-magneticmaterial, usuallyaluminum alloy, glass,or ceramic, and arecoated with a shallowlayer of magneticmaterial typically 10–20 nm in depth, with anouter layer of carbon forprotection.

The factors that limit the time to access the data on a hard disk drive (Access time) are mostly related to the mechanical nature of the

Access time can be improved by increasing rotational speed.

Defragmentation is also a procedure used to minimize delay in retrieving data by moving related items to physically proximate areas on the disk.

A USB flash drive is a data storage device that includes flash memory with an integrated Universal Serial Bus (USB) interface. USB flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g.

A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case.

1 USB Standard-A plug

2 USB mass storage controller device

3 Test points

4 Flash memory chip

5 Crystal oscillator

6 LED

7 Write-protect switch (Optional)

8 Space for second flash memory chip

Compared to hard drives, flash drivesuse little power, have no fragile movingparts, and for most capacities are smalland light. These properties make themsuitable for transporting data fromplace to place and keeping the datareadily at hand.

Most personal computerssupport USB as of 2012. Flash drivesimplement the USB mass storage deviceclass so that most modern operatingsystems can read and write to themwithout installing device drivers.

Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before the drive fails.

A drawback to the small size of flash drives is that they are easily misplaced, left behind, or otherwise lost.

USB flash drives are more expensive per unit of storage than large hard drives.

1. Secure storage of data, application and software files

2. Personal data transport

3. Application carriers

4. Booting operating systems

5. Media storage and marketing

6. Backup

Read-only memory (ROM) is a classof storage medium used in computers and otherelectronic devices. Data stored in ROM cannot bemodified, or can be modified only slowly or withdifficulty, so it is mainly used todistribute firmware.

MROM

PROM

EPROM

EEPROM

FLASH ROM

Mask ROM (MROM) is a type of read-only memory (ROM) whose contents are programmed by the integrated circuit manufacturer (rather than by the user).

A programmable read-only memory (PROM) or fieldprogrammable read-only memory (FPROM) or one-time programmable non-volatile memory (OTPNVM) is a form of digital memory where the settingof each bit is locked by a fuse or antifuse. SuchPROMs are used to store programs permanently.

A typical PROM comes with all bits reading as "1".Burning a fuse bit during programming causes thebit to read as "0". The memory can be programmedjust once after manufacturing by "blowing" thefuses.

An EPROM (rarely EROM), or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off. In other words, it is non-volatile.

Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source (such as from a mercury-vapor light).

EPROMs are easily recognizable by the transparent fused quartz window in the top of the package, through which the silicon chip is visible, and which permits exposure to UV light during erasing.

Window

EEPROM stands for Electrically Erasable Programmable Read-Only Memory.

EEPROM is user-modifiable read-only memory (ROM) that can be erased and reprogrammed (written to) repeatedly through the application of higher than normal electrical voltage generated externally or internally in the case of modern EEPROMs.

EPROM usually must be removed from the device for erasing and programming, whereas EEPROMs can be programmed and erased in-circuit.

Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data.

It is mainly use in USB flash drive mainly in pen drives & sd cards.

Random-access memory (RAM) is a form of computer data storage. A random-access device allows stored data to be accessed in very nearly the same amount of time for any storage location, so data can be accessed quickly in any random order.

One can read and over-write data in RAM.

RAM

SRAM DRAM

Static random-access memory (SRAM) is a type of semiconductor memory that uses bistable latching circuitry to store each bit. The term static differentiates it from dynamic RAM (DRAM) which must be periodically refreshed.

Each bit in an SRAM is storedon four transistors (M1, M2,M3, M4).

Two additionalaccess transistors serve tocontrol the access to astorage cell during read andwrite operations.

Thus a typical SRAM usessix MOSFETs to store eachmemory bit.

So the size of SRAM is biggerthan DRAM.

Advantages:

1. More faster than DRAM.

2. Do not require to refresh the data like DRAM.

3. Less power consumes.

Disadvantages:

1. More costly than DRAM.

2. Less dance than DRAM.

3. More complex structure than DRAM.

• Hence SRAM is generally not used for the computer as a RAM.• But they are used as cache memory in PC.

Dynamic random-access memory (DRAM) is atype of random-access memory that storeseach bit of data in a separate capacitor withinan integrated circuit. The capacitor can beeither charged or discharged; these twostates are taken to represent the two valuesof a bit, conventionally called 0 and 1.

Since capacitors leak charge, the informationeventually fades unless the capacitor chargeis refreshed periodically.

Advantages:

1. More cheaper than SRAM.

2. More dance than SRAM.

3. Less complex structure than SRAM.

4. Compact in size

• Hence DRAM is generally used for the computer as a RAM.Because they are suitable for large data capacity.

• The speed of DRAM is generally 633MHz.

Disadvantages:

1. Less faster than SRAM.

2. Require to refresh the data as the charge on capacitor leak.

3. More power consumes.

Magnetic Tape – this is a cheap method of storing large amounts of data (typically 26 gigabytes) and is often used as a ‘backing store’ for large and mainframe computers.

Zip drives are similar to floppy drives and use special (and rather expensive) floppy disks that can hold between 100 megabytes and 2 gigabytes of data.

Thank You