presentation on memory units.

1. PRESENTATION ON
MEMORY UNITS
Presented by
Krishna

2. INTRODUCTION
 In computing memory refers to the physical
devices used to store programs (sequences of
instructions) or data (e.g. program state
information) on a temporary or permanent
basis for use in a computer or other digital
electronic device.

3. TYPES OF MEMORY
 There are two types of Memory.
 They are :
 Primary or main Memory &
Secondary Memory

5. PRIMARY OR MAIN MEMORY
 Main memory is divided into two parts :
 Random Access memory (RAM), should be
better known as Read Write Memory (RWM).
 Read Only Memory (ROM) .

6. RANDOM ACCESS
MEMORY
(RAM)
 A RAM memory chip is an integrated circuit
(IC) made of millions of transistors and
capacitors.
 RAM is volatile memory, which means that it
requires
a steady flow of electricity to maintain its
contents.
As soon as the power is turned off, whatever
data was in
RAM is lost.

7. TYPES OF RAM
 STATIC RAM
 Semi conductor memory
 Uses flip flop to store each bit of memory so
does not need to be periodically refreshed
 Fast and consumes low power
 Expensive and has complex structure(6
transistors) so not used for high capacity
applications

8. DYNAMIC RAM
 Stores each bit of memory in capacitor in an
intrgrated circuit
 Real capacitors leak charge so capacitors
need to be refreshed periodically
 Simple structure (1 capacitor and 1 transistor
per bit) so it has very high density

9. READ ONLY MEMORY
(ROM)
 New contents cannot be added
 Used to store the instructions of routine type,
permanent in nature and used to control or
supervise the hardware

10. TYPES OF ROM
 PROGRAMMABLE READ ONLY MEMORY
(PROM)
 Programmed to record the information using a
facility PROM – programmer
 Once the information is recorded it cannot be
changed

11. ERASABLE PROGRAMMABLE
READ ONLY MEMORY (EPROM)
 Information can be erased and chip can be
reprogrammed to record different information
using PROM programmer
 In formation is erased using UV radiations
 It is of two types- Ultra Voilet Erasable
Programmable Read Only Memory (UEPROM)
and Electrically Alterable Programmable Read
Only Memory (EAPROM

12. ELECTRICALLY ERASABLE
PROGRAMMABLE READ ONLY MEMORY
(EEPROM) Memory is erased by electrical signals
 Provides easy means to store temporary or
permanent information in the form of ROM
memory
 EEPROM is just like a flash memory.
 Flash Memory is a special types of EEPROM
that can be erased and reprogrammed in
blocks instead of one byte at a time.

13. CACHE MEMORY
 Faster and expensive than RAM
 It improves the computer’s performance and is
less than 512 KB
 Processor can use it to store frequently
accessed data and programs instructions
 It is of two types – L1 / primary cache(inside
microprocessor) and L2/ secondary cache(in
the mother board or near the microprocessor)

15. Flash memory
 Flash memory is an electronic non-volatile computer
storage medium that can be electrically erased and reprogrammed.
 Introduced by Toshiba in 1984, flash memory was developed
from EEPROM (electrically erasable programmable read-only
memory). There are two main types of flash memory, which are
named after the NAND and NOR logic gates. The internal
characteristics of the individual flash memory cells exhibit
characteristics similar to those of the corresponding gates.
15

16. SECONDARY MEMORY
By:ppkl
16

17. History of secondary memory
17
 The Selectron tube
 The Selectron tube had a capacity of 256 to
4096 bits (32 to 512 bytes). The 4096-bit
Selectron was 10 inches long and 3 inches
wide. Originally developed in 1946, the
memory storage device proved expensive and
suffered from production problems, so it never
became a success.

18. Punch cards
18
 Early computers often used punch cards for
input both of programs and data. Punch cards
were in common use until the mid-1970s. It
should be noted that the use of punch cards
predates computers. They were used as early
as 1725 in the textile industry (for controlling
mechanized textile looms).

19. Punched tapes
19
 Same as with punch cards, punched tape was
originally pioneered by the textile industry for
use with mechanized looms. For computers,
punch tape could be used for data input but
also as a medium to output data. Each row on
the tape represented one character.

20. Magnetic drum memory
20
 Invented all the way back in 1932 (in Austria), it was widely used in
the 1950s and 60s as the main working memory of computers. In
the mid-1950s, magnetic drum memory had a capacity of around 10
kB.

Above left: The magnetic Drum Memory of the UNIVAC
computer. Above right: A 16-inch-long drum from the IBM 650
computer. It had 40 tracks, 10 kB of storage space, and spun at
12,500 revolutions per minute.

21. Flash memory
 Flash memory is an electronic non-volatile computer
storage medium that can be electrically erased and reprogrammed.
 Introduced by Toshiba in 1984, flash memory was developed
from EEPROM (electrically erasable programmable read-only
memory). There are two main types of flash memory, which are
named after the NAND and NOR logic gates. The internal
characteristics of the individual flash memory cells exhibit
characteristics similar to those of the corresponding gates.
21

22. Working of flash memory
 Flash memory is a type of EEPROM chip, which stands
for Electronically Erasable Programmable Read Only
Memory. It has a grid of columns and rows with a cell
that has two transistors at each intersection (see image
below).
 The two transistors are separated from each other by a
thin oxide layer. One of the transistors is known as
a floating gate, and the other one is the control gate.
The floating gate's only link to the row, or word line, is
through the control gate. As long as this link is in place,
the cell has a value of 1. To change the value to a 0
requires a curious process called Fowler-Nord heim
tunneling.
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24. Types of flash memory
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 There are two main types of flash memory
 NOR and NAND

25. Nor memory
25
 NOR flash is the faster memory, but
when having to erase and write data, it
takes longer.
 Developed to replace read only memory
 Full address and data buses allow
random access to any memory location
 Can access any memory cell
 Slow sequential access

26. Nand memory
 The storage capacity of NAND is a lot more
than that of NOR, but the random access is
slow for it.
 Developed to replace hard disks
 Sequential-accessed command and data
registers replace the external bus of NOR
 Decreases chip real estate
 Can only access pages
 Faster sequential access
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27. Types of flash memory
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 SD Cards
 Compact Flash
 Cards
 USB Drives
 Memory Sticks
 Smart Media Cards

28. Categories Of
Storage28
 • Magnetic
 – Floppy disks
 – Zip disks
 – Hard drives
 • Optical
 – CD-ROM
 – DVD
 • Solid state storage devices
 – USB Key

29. Magnetic storage
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 Magnetic storage (or magnetic recording) is
the storage of data on a magnetized medium.
Magnetic storage uses different patterns
of magnetization in a magnetizable material to
store data and is a form of non-volatile
memory. The information is accessed using
one or more read/write heads.

30. Magnetic drives
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31. Magnetic disc
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 Flat, circular platter with metallic coating
 that is rotated beneath read/write heads
 Random access device; read/write head
 can be moved to any location on the
 platter
 Hard disks and floppy disks
 Cost performance leader for generalpurpose
 on-line secondary storage

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 Magnetic Drives: Storage Capacities
 Floppy disks
 ~ 1 MB
 Hard drives
 ~80 – 500 GB

33. Floppy discs
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 A floppy disk, also called a diskette, is a disk storage medium
composed of a disk of thin and flexible magnetic storage medium,
sealed in a rectangular plastic carrier lined with fabric that removes
dust particles. Floppy disks are read and written by a floppy disk
drive(FDD).
 Floppy disks, initially as 8-inch (200 mm) media and later in 5¼-inch
(133 mm) and 3½-inch (90 mm) sizes, were a ubiquitous form of
data storage and exchange from the mid-1970s well into the 2000s

34. Hard disks
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 A hard disk drive (HDD)[b] is a data storage device used for storing
and retrieving digital information using rapidly rotating disks
(platters) coated with magnetic material.[2] An HDD retains its
data even when powered off. Data is read in a random-access
manner, meaning individual blocks of data can be stored or
retrieved in any order rather than sequentially. An HDD consists of
one or more rigid ("hard") rapidly rotating disks (platters)
with magnetic heads arranged on a moving actuator arm to read
and write data to the surfaces.

35. Optical Drives
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 CD's (Compact Disk)
 ~ 700 MB storage
 CD-ROM (read only)
 CD-R: (record) to a CD
 CD-RW: can write and erase CD to reuse it
(rewritable)
 • DVD(Digital Video Disk)

36. Compact disc(cd)
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 Compact disc (CD) is a digital optical disc data storage format. The
format was originally developed to store and play only sound
recordings but was later adapted for storage of data (CD-ROM).
Several other formats were further derived from these, including
write-once audio and data storage (CD-R), rewritable media (CD-
RW), Video Compact Disc (VCD), Super Video Compact Disc
(SVCD), Photo CD, Picture CD, CD-I , and Enhanced Music CD.
Audio CDs and audio CD players have been commercially available
since October 1982.
 Standard CDs have a diameter of 120 millimetres (4.7 in) and can
hold up to about 80 minutes of uncompressed audio or about
700 MB of data. The Mini CD has various diameters ranging from
60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD
singles, storing up to 24 minutes of audio or delivering device
drivers.

37. DVD (Digital Video Disk)
37
 DVD (sometimes explained as "digital video disc" or "digital
versatile disc"[4][5]) is a digital optical disc storage format,
invented and developed by Philips, Sony, Toshiba,
and Panasonic in 1995. DVDs can be played in multiple types
of players, including DVD players. DVDs offer higher storage
capacity than compact discs while having the same
dimensions.
 Pre-recorded DVDs are mass-produced using molding
machines that physically stamp data onto the DVD. Such
discs are known as DVD-ROM, because data can only be
read and not written or erased. Blank recordable DVD discs
(DVD-R and DVD+R) can be recorded once using a DVD
recorder and then function as a DVD-ROM. Rewritable DVDs
(DVD-RW, DVD+RW, and DVD-RAM) can be recorded and
erased many times.

38. Blu-ray Technology
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 Blu-ray Disc (BD) is a digital optical disc data storage format
designed to supersede the DVD format, in that it is capable of
storinghigh-definition video resolution (1080p). The plastic
disc is 120 mm in diameter and 1.2 mm thick, the same size
as DVDs andCDs.[4] Conventional (pre-BD-XL) Blu-ray Discs
contain 25 GB per layer, with dual layer discs (50 GB) being
the industry standard for feature-length video discs. Triple
layer discs (100 GB) and quadruple layers (128 GB) are
available for BD-XL re-writer drives.[5] The name Blu-ray
Disc refers to the blue laser used to read the disc, which
allows information to be stored at a greater density than is
possible with the longer-wavelength red laser used for DVDs.
The main application of Blu-ray Discs is as a medium for
video material such as feature films and physical distribution
of video games for the PlayStation 3, PlayStation 4 and Xbox
One. Besides the hardware specifications, Blu-ray Disc is
associated with a set of multimedia formats.

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