Computer Memory

1. Presented By:-
NITESH KUMAR PANDEY

2. MemoryMemory
• Computer Memory is any physical device capable
of storing information temporarily or permanently.
• Computer memory is storage unit where we stored
and retrieve the information.
• Some times unallocated space of hard disk is used
as virtual memory also known as page file.

3. Kinds of MemoryKinds of Memory
• Primary Memory :- it is accessible directly by the
processing unit.
Ex:- RAM
• Secondary Memory:- It is a type of memory where
we can stored data on permanently basis and it is
also used to stored large amount of data. It is
accessed by primary Memory and it is also known
as Auxiliary memory.
Ex. HDD, Floppy drive etc.

4. Primary vs. SecondaryPrimary vs. Secondary
• Primary memory is
accessible directly by
the processing unit.
• Primary memory is also
called main memory.
• The size of primary
memory is less.
• This is faster and
expensive.
• Secondary memory
accessible by primary
memory.
• Secondary memory is
called Auxiliary
memory.
• The size of secondary
memory is more.
• This is slower and
cheaper.

5. Primary vs. SecondaryPrimary vs. Secondary
cont…cont…
• This is known as
semiconductor
memory.
• It is volatile memory.
• Examples:- RAM & ROM
• This is known as
magnetic memory.
• It is non-volatile
memory.
• Example:- HDD, FDD
etc.

6. RAM(Random AccessRAM(Random Access
Memory)Memory)
• The read & write m/y of a computer is called RAM.
• The users can write information into RAM and read
information from it.
• It possesses random access property.
• In this m/y can be accessed on a random manner.
• It is a volatile memory.

7. Types of RAMTypes of RAM
• SRAM(static random access memory):
The information need to be refreshed.
In this it retain stored information only as long as the
power supply is on.
• DRAM(dynamic random access memory):
The information has been refreshed after every
few second otherwise the information will be
erased.
• SRAM is costlier but has higher speed than DRAM.

8. ROM(Read OnlyROM(Read Only
Memory)Memory)
• It is essential component of memory unit.
• Whenever the computer is switched on is searches
for the require instruction.
• This m/y is permanent & not erased when the
system is switched off i.e. it is non volatile in nature.
• As appeared with the name it is read type of
memory i.e. it can read only & can't be written or
altered by user/programmer.

9. Types of ROMTypes of ROM
• Mainly four types of rom-
• PROM(Programmable read only memory):-
In this type of rom the information is stored by
programmer after manufacturing.
And cannot be altered/erased later on.
• EPROM(Erasable PROM):-
It is similar to prom but the information can be erased
after programmed using special tools which emits
UV light and can be reprogrammed.
`

10. Types of ROM cont…Types of ROM cont…
• EEPROM(Electrically Erasable PROM):-
It is kind of EPROM but the difference is that the
information can be erased using electric current. Its
main advantage is it doesn’t need to remove from
socket while reprogramming.
• EAPROM(Electrically alterable PROM):-
As compared to EPROM & EEPROM the information
stored here can be altered later.

11. Volatile vs. non-volatileVolatile vs. non-volatile
memorymemory
• Memory can be either volatile and non-volatile
memory.
• Volatile memory is a temporary memory that loses
its contents when the computer or hardware
device loses power. RAM is a good example of a
volatile memory.
• non-volatile memory keeps its contents even if the
power is lost. HDD is good example of non-volatile
memory.

12. Magnetic Media & OpticalMagnetic Media & Optical
MediaMedia
• Magnetic Media: which stores the binary data on a
disk or tape coated with a material that can be
magnetized depending on whether 0 or 1 is stored.
Ex. Floppy Disk, HDD
• Optical Media: which stores the binary data in a
surface that reflects laser light differently depending
on whether 0 or 1 is stored.
e.g., CD ROM, DVD ROM

13. Optical DiskOptical Disk
• CD-ROM: It is stand for Compact Disk Read Only
Memory
• And the data is stored by using a laser beam.
• We use laser beam to read the data. When the
beam travels from the direction of the base and
reaches the pits, the pits on the metal layer reflects
the beam like a mirror.
• Digit '1' at the edge of pits and digit '0' elsewhere.
This is the basic mechanism of information storage
and retrieval using CD-ROMs.

14. Floppy DiskFloppy Disk
• It is also known as Diskette.
• It is developed in the late 1960s. Where 8-inchs in
diameter.
• A floppy disks are made of flexible plastic which is
coated with magnetic oxide.
• The flexible disk is enclosed within a square plastic.
• Floppy disk, initially as 8-inch(200mm) media and
later in 5.25-inch(133mm) and 3.5-inch(90mm)

15. HARD DISK DRIVEHARD DISK DRIVE
• A Hard Disk Drive(HDD) is data storage device
• Used for storing and retrieving digital information
using rapidly rotating discs(platters) coated with
magnetic material.
• An HDD retains its data when powered off
• Data is read in random-access manner
• That means individual block of data can be stored
and retrieved in any order
• It introduced by IBM in 1956

16. HDD DIAGRAMHDD DIAGRAM

17. PLATTERSPLATTERS
• HDD design consists of a spindle that holds flat
circular disks, also called platters
• The platters are made from a non-magnetic
material, usually aluminum alloy, glass.
• Today, the platters in most consumer HDDs spin in
the range of 5,400 rpm to 7,200 rpm.
• Information is written to and read from a platter as it
rotates past devices called read-and-write heads

18. WINCHESTERWINCHESTER
• In 1973, IBM introduced a new type of HDD
codenamed "Winchester".
• Its primary distinguishing feature was that the disk
heads were not withdrawn completely from the
stack of disk platters when the drive was powered
down.

19. PlattersPlatters

20. • There are two most common form factor :-
3.5-inch used in desktop computers and
2.5-inch used in laptops
• HDD available in different capacity like 10GB,
40GB,120GB,360GB,500GB,750GB,1TB,2TB,
3TB and 4TB

21. ERROR HANDLINGERROR HANDLING
• Modern drives make extensive use of error
correction codes (ECCs).
• While the errors in the bad sector are still few
enough that the ECC can recover the data without
loss.

22. SMARTSMART
• The S.M.A.R.T-Self-Monitoring, Analysis and
Reporting Technology system counts the total
number of errors in the entire HDD fixed by ECC and
the total number of remapping, as the occurrence
of many such errors may predict HDD failure.