Memory refers to the physical devices used to store programs and data in a computer. Main memory is divided into RAM and ROM. RAM is read-write memory that uses transistors and capacitors to store each bit. There are two types of RAM: static RAM which does not need refreshing but is expensive, and dynamic RAM which needs refreshing but has higher density. ROM is read-only and stores permanent instructions. There are also programmable ROMs like PROM, EPROM, and EEPROM that can be programmed and erased in different ways. Caches and secondary storage supplement main memory and improve performance. Common secondary storage devices include magnetic disks, tapes and optical discs.

2. 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.

4.  Main memory is divided into two parts :
 Random Access memory (RAM), should
be better known as Read Write Memory
(RWM).
 Read Only Memory (ROM) .

5.  A RAM memory chip is
an integrated circuit
(IC) made of millions of
transistors and
capacitors. In the most
common form of
computer memory,
dynamic random
access memory
(DRAM), a transistor
and a capacitor are
combines to create a
memory cell, which
represents a single bit
of data.

6.  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

7.  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

8.  New contents cannot
be added
 Used to store the
instructions of routine
type,permanent in
nature and used to
control or supervise
the hardware

9.  PROGRAMMABLE
READ ONLY MEMORY
(PROM)
 Programmed to
record the
information using a
facility PROM –
programmmer
 Once the
information is
recorded it cannot
be changed

10.  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)

11.  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

12.  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)

13.  It supplements the
main memory. It is
permanent
memory.
 Programs, data
entered into the
system,
intermediate results
and final results
produced are
stored in the
secondary memory

14.  MAGNETIC BASED
STORAGE DEVICES
 Prepared using
using formatting
 Data is recorded
on disk in
concentric
circular bands
called tracks.
 MAGNETIC TAPE
 FLOPPY DISK
 HARD DISK

15.  OPTICAL STORAGE
MEDIA
 Stores large amount of
data in some formats as
much as the entire hard
disk
 Reads data by focusing
a laser- generated
beam of light on light on
disc’s surface
 CD- ROM discs
 DVD- ROM discs

16.  Ranking of
computer memory
devices, with
devices having
the fastest access
time at the top of
hierarchy, and
devices with
slower access time
but larger
capacity and
lower cost at
lower levels

17. THANKS