The document discusses different types of computer memory. It defines memory as the component that stores instructions and data. There are two main types of memory: primary memory (RAM) that is directly accessed by the CPU, and secondary memory like hard disks. RAM is volatile and temporarily stores data during use, while ROM is non-volatile and stores permanent instructions. The document outlines different RAM technologies like DRAM, SRAM, and MRAM and compares their characteristics. It also discusses cache memory, ROM, flash memory, and CMOS memory.

1. 1
Memory
A component in the computer used for
storing instructions and data is called
memory.
Ms-Nazia

3. 3
Types Memory
 Memory can be divided into two
types.
 Primary memory
 Secondary memory

4. Primary Memory
 Primary memory is computer memory that is
accessed directly by the CPU. This includes several
types of memory, such as the processor cache and
system ROM. ... RAM, or random access memory,
consists of one or more memory modules that
temporarily store data while a computer is running.

5. 5
Types of Memory
 There are two types of memory in computer that are as follows:
 Volatile Memory: It loses its contents when computer is turned off. RAM is
the most common type of volatile memory
 Non-volatile Memory: It does not lose its contents when computer is
turned off. ROM, Flash memory and CMOs are examples of non-volatile
memory.

6. 6
RAM
 RAM stands for Random Access Memory also called direct access memory.
 Random-access memory (RAM) is a form of computer data storage that
stores data and machine code currently being used. A random-access memory
device allows data items to be read or written in almost the same amount of time.
 Random access means that each individual byte in entire memory can be
accessed directly.
 RAM is a volatile memory. It means that its contents are lost when the power is
turned off.
 RAM is read/write memory.
 CPU can read data from RAM and write data to RAM. It is used to store data
and instructions while it is being executed.
 RAM is also called main memory or primary memory

7. 7
RAM
 RAM plays very important role in the processing speed of computer.
 A bigger RAM size provides larger amount of space for processing. So the
processing speed is increased. The amount of data that can be stored in
RAM is measured in bytes.
 Most desktop computers typically have up to 2GB of RAM. It also allows
the addition of more memory if need.

8. 8
Types Of RAM
 RAM is built by two different techniques:
1. DRAM
2. SRAM
3. MRAM

9. 9
DRAM
 DRAM stands for Dynamic Random Access Memory. It is a type
of memory that is used in most computers. It is least expensive
type of RAM.
 DRAM requires electric current to maintain its electrical state.
 The electrical charge of DRAM decreases with time that may
result in loss of data.
 DRAM is recharged and refreshed again and again to maintain its
data. The processor cannot accessed the data of DRAM when it
is being refreshed. That is why it is slow.

10. DRAM
 Dynamic random-access memory (DRAM) is a type of
memory that stores each bit of data in a separate tiny capacitor within
an integrated circuit.
 The capacitor can either be charged or discharged; these two states are
taken to represent the two values of a bit, conventionally called 0 and 1.
 The electric charge on the capacitors slowly leaks off, so without
intervention the data on the chip would soon be lost. To prevent this,
DRAM requires an external memory refresh circuit which periodically
rewrites the data in the capacitors, restoring them to their original
charge.
 Because of this refresh requirement, it is dynamic memory as opposed
to static random-access memory (SRAM) which does not require data
to be refreshed.
 DRAM is volatile memory, since it loses its data quickly when power is
removed.

11. SRAM
 SRAM stands for Static Random Access Memory.
 SRAM that retains data bits in its memory as long as power
is being supplied.
 Unlike dynamic RAM, it does not need to be refreshed.
 While SRAM can operate at higher speeds than DRAM, it is
more expensive to manufacture because of its complex
internal structure, so most of the RAM on the
motherboard is DRAM.
 SRAM is most often found in hard drives. It is also found in
compact discs (CD’s), printers, modem routers, digital
versatile discs (DVD’s) and digital cameras.

12. 12
SRAM
 It can store data without any need of frequent recharging. CPU
does not need to wait to access data from SRAM during the
processing. That is why it is faster than DRAM.
 It utilizes less power than DRAM.
 SRAM is more expensive.
 It is normally used to build a very fast memory known as cache
memory.

13. 13
MRAM
 MRAM stands for Megnetoresistive Random Access Memory.
 It can store data using magnetic charges instead of electrical
charges.
 MRAM uses far less power than other RAM technologies that
make it ideal of portable computing devices.
 It also has greater storage capacity.
 It has faster access time than RAM.
 It utilizes less power than DRAM.
 It retains its contents when the power is removed from computer.

14. 14
Difference Between SRAM & DRAM
 The difference between SRAM and DRAM is as follows:
S.# SRAM DRAM
1. It is faster than DRAM It is slower than DRAM
2. It is more expensive It is less expensive
3. It does not need to be power
refreshed
It has to be refreshed after each read
operation
4. It utilizes less power It utilizes more power
5. It holds data indefinitely(unlimited
period of time) as long as the
computer is turned on
It holds data dynamically(powerful)
not indefinitely
6. It is more complex and less
compact(compress)
It is less complex and more compact

15. 15
ROM
 ROM stands for read only memory. The instructions in ROM
prepare the computer for use. These instructions can only be read
but cannot be changed or deleted.
 It is not possible to write new information or instructions into the
ROM.
 ROM stores data and instructions permanently. When the computer
is switched off, the instructions stored in the ROM are not lost .
Therefor, ROM is called non-volatile memory.
 The information in ROM is stored by the manufacturer. When the
computer is switched on, the instructions in the ROM is
automatically loaded into the memory of the computer.

16. 16
ROM
 ROM contains the small set of instructions called ROM BIOS.
 BIOS stands for Basic Input / Output System. These instructions tell
the computer how to access hard disk, find operating system and
load in it RAM.
 Once data has been written onto a ROM chip, it cannot be removed
and can only be read. Unlike main memory (RAM),ROM retains its
contents even when the computer is turned off. ROM is referred to as
being nonvolatile, whereas RAM is volatile.

17. 17
Types of ROM
 Different types of ROM are as follows:
1. PROM (Programmable Read Only Memory)
2. EPROM (Erasable Programmable Read Only Memory)
3. EEPOM (Electronically Erasable Programmable Read Only
Memory)

18. 18
PROM
 PROM stands for programmable Read Only Memory. This form of
ROM is initially blank. The user and manufacturer can write data
and program on it using special device.
 The user can write data and instructions only once. If there is any
error in writing the instruction, the error cannot be removed from
PROM. The chip becomes unusable.

19. 19
EPROM
 EPROM stands for Erasable Read Only Memory. This form of
ROM is initially blank. The user and manufacturer can write data
and program on it using special device.
 The data and programs written on it can be erased with special
devices using ultraviolet rays. The user can write new program on
it.
 EPROM can be erased by exposing it to ultra-violet light for a
duration of up to 40 minutes. Usually, an EPROM eraser achieves this
function.

20. 20
EEPROM
 EEPROM stands for Electronically Erasable Programmable Read
Only Memory.
 In this memory, user can erase and write instructions with the help
of electrical pulses.
 If there is any error in writing the instructions, the user can erase
the contents electronically. The contents of EEPROM can be
modified easily.
 EEPROM is programmed and erased electrically. It can be erased and
reprogrammed about ten thousand times. Both erasing and
programming take about 4 to 10 ms (millisecond).

21. 21
Difference Between PROM & EPROM
 The difference between PROM and EPROM is as follows:
S.# PROM EPROM
1. PROM is programmable read only
memory
EPROM is erasable programmable
read only memory
2. The user can write instructions on
PROM only once
The user can write instructions many
times on EPROM
3. The instructions written by the user
can not be erased from PROM
The instructions written by the user
can be erased from EPROM
4. If there is an error while writing on
PROM, it becomes unusable.
If there is an error while writing on
EPROM, it becomes usable.
5. It provides less usability as
instructions are written only once.
It provides more usability as
instructions are written many times.

22. 22
Difference Between RAM & ROM
 The difference between RAM and ROM is as follows:
S.# RAM ROM
1. RAM is a temporary memory. ROM is a permanent memory.
2. RAM enables data to be both read
and written to memory or data can
be changed or deleted.
The instructions written in ROM can
only be read but cannot be changed or
deleted
3. Instructions in the RAM is
continuously changing as different
programs are executed and new
data are processed.
It is not possible to write new
information or new instructions into
the ROM, so ROM is non-volatile
memory.
4. When the power is turned off, all
the programs and data are erased
from RAM. Therefore, RAM is a
volatile memory.
When the power is turned off, the
instructions stored in ROM are not
lost, therefore ROM is non-volatile
memory
5. The instructions are written into
RAM at the time of execution.
The instructions are written into ROM
at manufacturing time.

23. 23
Cache Memory
 A cache (pronounced Cash) is a small very fast memory. It is designed
to speed up the transfer of data and instructions. It is located inside or
close to the CPU chip. It is more expensive and faster than RAM.
 The data and instructions that are recently or most frequently used by
CPU are stored in cache.
 The data and instructions are retrieved from RAM when CPU uses
them for first time. A copy of that data or instructions is stored in cache.
The next time the CPU needs that data or instructions, it first looks in
cache.
 If the required data is found there, it is retrieved from cache memory
instead of main memory. It speeds up the working of CPU.

24. 24
Flash Memory
 Flash memory is a type of non-volatile memory. It can be erased
electronically like EEPROM.
 Most computer use it to store startup instructions as it allows
computer to update its contents easily.
 Flash memory chips also stores data and programs on mobile
computer and other devices such as smart phone, portable media
players, printers and digital cameras etc.
 The data in smart phones are used on flash memory. Some
portable media players store music on flash memory chips.

25. Flash Memory
 Flash memory is a non-volatile memory chip used for
storage and for transfering data between a personal
computer (PC) and digital devices. It has the ability to
be electronically reprogrammed and erased. It is often
found in USB flash drives, MP3 players, digital
cameras and solid-state drives.
 Flash memory is a type of electronically erasable
programmable read only memory (EEPROM), but may
also be a standalone memory storage device such as a
USB drive. EEPROM is a type of data memory device
using an electronic device to erase or write digital data.

26. 26
CMOS
 CMOS stands for Complementary Metal-Oxide Semiconductor.
 CMOS technology provides high speed and consumes less power.
 It stores configuration information of computer. The information
include the types of disk drives, keyboard and monitor, current date
& time and other startup information required during boating
process.
 CMOS chip uses battery to retain information even when the
computer is turned off.
 The information in CMOS can be changed.

27.  CMOS (complementary metal-oxide-semiconductor)
is the term usually used to describe the small amount
of memory on a computer motherboard that stores the
BIOS settings. Some of these BIOS settings include the
system time and date as well as hardware settings.
