It's a simple power point presentation on the memory unit of the computer of class 11. Hope you will find it helpful.

2. What is Memory?
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 Memories.
Memory
Primary
RAM
-SRAM
-DRAM
ROM
-PROM
-EPROM
-EEPROM
Secondary
Sequential
e.g. Magnetic
Tape
Random
-Magnetic
-Optical

4. Main Memory
MAIN MEMORY or also known as PRIMARY
MEMORY is one of the very important parts
of computer. Without it you can not run your
computer as all the programmes to start your
computer are installed in it. Also it is volatile
in nature i.e. it will store information till it is
on. And then after switching off, it forgets
everything. It is only temporary not
permanent. There are two types of main
memories-
1. Random Access Memory(RAM)
2. Read Only Memories(ROM)

5. Random Access Memory
Some features of RAM are-
1. It stores data temporarily.
2. It is volatile in nature.
3.It stores initial, intermediate and final data of the
process.
There are two types of RAM-
1. STATIC RAM( Refreshes on the command of user )
2.DYANMIC RAM( Refreshes itself in every few
milliseconds )

6. Static RAM
It refreshes itself on the command of the
user. It contains the command until it is
commanded to refresh itself. It do not cause
any type of delay in the process by refreshing
it self. It is costlier. It is used in launching of
rockets, where there is no place for even a
fraction of delay in process.

7. Dynamic RAm
It refreshes itself in every few milliseconds,
to arrange all the data and to make the full
use of the processor and process the data as
fast as possible and also to utilize all the
memory of the computer. It is comparatively
cheaper in price.
It is used in common PCs.

8. Read Only Memory
Features of ROM are-
1. It stores data permanently.
2.It is non-volatile in nature.
3.It stores the code to run the computer,
BIOS code [ Basic Input Output System ]
There are three types of ROM-
1. Programmable ROM.
2.Erasible PROM.
3.Electronically EPROM.

9. Programmable ROM
It is a use and throw ROM chip. If the
programme written in the chip is in use, it’s
will work but soon as there need a change in
the programme, a new programme will have to
be written on other chip which creates a lot
of pollution as it can not be recycled. To solve
this problem EPROM was invented.

10. Erasable PROM
To avoid all the scrap produced by PROM,
EPROM was invented. The programme
written in it can be erased by the action of
ultra violet rays on the chip. The problem
with it was that, by the action of UV rays
on it, the chip was damaged, and could not
be used after 2-3 times of erases. And also,
if you want erase a little part of the
programme, it will remove all the data and
you will have to start from the starting
point.

11. Electrically EPROM
To resolve the problem of EPROM, EEPROM
was invented, which can erase the data
electronically, then rewriting the programme
in it. If there has to be a little change in
chip, the whole data is not to be erased,
only the effective part can erased and
rewritten on it.

12. Secondary Memory
Since Primary memory has a limited storage capacity and it is
not permanent, Secondary storage devices are used to store
large amounts of data permanently. It is not non-volatile in
nature thus it stores all the data permanently in it after the
computer is off. There are various type of Secondary memory
devices available nowadays.

13. Random memory
RANDOM MEMORY-
Random memory consists of two types-
1. MAGNETIC FORM-
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. E.G. Hard Disk,
Floppy Disk, Recording Studios etc.

14. 2. OPTICAL FORM-
The compact disks or CDs are optical
way of storing the information. The CDs
are relatively very cheap and handle up to
huge sum of input. i.e. 700 mb – 100gb (
blue ray). There are three types of CDs-
1. CD-ROM ( compact disk read only
memory )
2.CD-R ( Recordable )
3.CD-RW ( Rewritable)