The document provides an overview of internal and external memory in computers, detailing types such as RAM, ROM, cache memory, and external storage options including magnetic and optical disks. Internal memory is directly accessible to the processor and is usually more expensive and smaller, while external memory offers larger storage capacity and retains data without power. Different types of memories like SRAM, DRAM, and various ROM forms are described, along with their characteristics and uses.

1. DIFFERENT TYPES OF
INTERNAL &
EXTERNAL MEMORY
Name:Mohitkumar Naik
Roll No:36

2. What is Internal Memory?
 Computer memory can be classified either as internal memory or as
external memory. The internal memory is the one that is directly
accessible to the processor via system bus and the external memory is
accessed via input-output channels of the computer.
 The internal memories of the computer are made up of semiconductor
material usually silicon. This memory is costlier and is usually small in
size as compared to the external memory.

3. Types Of Computer Memory

4. Random Access Memory (RAM)
 The RAM memory is the fastest but is a volatile memory. That means to
retain its content the RAM memory has to be provided with a constant
power supply. Once the power supply to this memory chip is switched off
this memory chip loses all its content.
 It is easy to read data from and write data into the RAM memory. The data
is read or written into the RAM memory using the electric signals. Further,
the RAM memory has two other forms DRAM and SRAM.

5. DRAM & SRAM
Dynamic Random Access Memory
(DRAM)
 It stores information as long as the
power is supplied Capacitors are
used to store data in DRAM.
 To store information for a longer
time, contents of the capacitor
need to be refreshed periodically.
 DRAM provides slow access speeds.
 These are cheaper
Static Random Access Memory
(SRAM)
 It stores information as long as the
power is supplied.
 Transistors are used to store
information in SRAM.
 Capacitors are not used hence no
refreshing is required.
 These are expensive

6. Read-Only Memory (ROM)
 Read-only memory (ROM) is a non-volatile memory which means
the memory cells of this memory chip do not require a power
supply to retain its bit value. As this is a read-only memory the
bit values of this memory can only be read and not be written or
modified.
 Like RAM the ROM also has some other forms such as
programmable ROM, erasable programmable ROM, electrically
erasable programmable ROM, and flash memory.

7. Programmable Read-
Memory(PROM)
A Memory chip on which data can be written only
once.
The difference between a PROM & ROM(Read-only
memory)is that a PROM is manufactured as blank
memory, whereas a ROM is programmed during the
manufacturing process.

8. Erasable Programmable Read
Memory(EPROM)
Erasable programmable read only memory, can be
read and written using electrical signals.
Well before a write operation is performed the
memory content of this memory chip are erased
to retain its initial state by exposing the
memory chip to the ultraviolet rays.

9. Electrically Erasable Programmable
ROM(EEPROM)
The electrically erasable programmable
ROM (EEPROM) is the ROM memory that can be erased
selectively and written multiple times. Unlike the
EPROM where the entire data gets erased when
exposed to the ultraviolet rays.
The EEPROM is a little complex when compared to the
EPROM as it requires different electrical voltage to
erase the data.

10. Cache Memory
The cache memory is a volatile memory that loses its
memory content once the power supply to the memory
unit is interrupted. The cache memory keeps the copies
of the recently accessed information from the main
memory.
The cache memory stores the frequently use
information. The cache memory is faster and costlier
and smaller than RAM memory.

11. What Is External Memory?
 External memory can also be known as secondary memory or backing store. It is used
to store a huge amount of data because it has a huge capacity. At present, it can
measure the data in hundreds of megabytes or even in gigabytes. The important
property of external memory is that whenever the computer switches off, then stored
information will not be lost. The external memory can be categorized into four parts:
 Magnetic Disk
 Optical Disk
 Optical Memory
 Magnetic Tape

12. Magnetic Disk
 A disk is a type of circular platter constructed by a nonmagnetic material,
which is known as a substrate. It is covered with a magnetic coating used to
hold the information.
 The substrate is traditionally constructed by aluminium or aluminium alloy
material. But recently, another material has been introduced, which is
known as glass substrates.
 It has the ability to increase disk reliability by improving the uniformity of a
magnetic film surface.It is used to reduce the errors of read-write by doing a
significant reduction in overall surface defects.
 It has better stiffness, which will help to reduce disk dynamics. It has the
great ability that it can withstand against shock and damage.

13. Optical Disk
 The optical disk storage system includes a rotating disk coated with a
diminished layer of metal that facilitates a reflective surface and a laser
beam, which is used as a read/write head for recording information onto
the disk. Unlike magnetic disk, the optical layer consists of a single long
track in the form of a spiral shape.
 The spiral shape of the track produces the optical disk applicable for
reading huge blocks of sequential information onto it, including music.

14. Optical Memory
 Optical memory is an electronic storage medium that uses a laser
beam to store and retrieve the data. If we classify the memory system
then optical memory comes under the external memory in the
computer system. Optical memory can be classified into many types.
 Examples of optical memories are:
 Compact Disk (CD),
 Digital Versatile Disk (DVD), and
 Bluray Disk (BD).

15. Magnetic Tape
 Magnetic tape is a type of physical storage media for different kinds
of data. It is considered an analog solution, in contrast to more recent
types of storage media, such as solid state disk (SSD) drives.
 Reading and writing techniques in the tape system is the same as the
disk system. Magnetic tape has been a major vehicle for audio and
binary data storage for several decades, and is still part of data
storage for some systems.

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