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.
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. 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.
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
10. 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
12. TYPES OF ROM
PROGRAMMABLE READ ONLY MEMORY
(PROM)
Programmed to record the information using a
facility PROM – programmmer
Once the information is recorded it cannot be
changed
14. 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)
15. 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
17. 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)
19. SECONDARY MEMORY
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
21. CLASSIFICATION
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
22. 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
23.
24. MEMORY HIERARCHY
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
