Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices.

1. R O MR e a d O n l y M e m o r y

2. Read-only memory (ROM) is a type of storage medium that
permanently stores data on personal computers (PCs) and other
electronic devices.
What is ROM?

3. • It is type of internal memory.
• The data and instructions in ROM are stored by the
manufacturer at the time of its manufacturing. This
data and programs cannot be changed or deleted after
wards.
• The data or instructions stored in ROM can only be
read but new data or instructions cannot be written
into it. This is the reason why it is called Read Only
Memory.

4. There are five basic ROM types:
ROM - Read Only Memory
PROM - Programmable Read Only Memory
EPROM - Erasable Programmable Read Only Memory
EEPROM - Electrically Erasable Programmable Read Only Memory
Flash EEPROM Memory
Types of ROM

5. ROM stores data and instructions permanently.
 When the power is turned off, the instructions stored in ROM are
not lost. That is the reason ROM is called non-volatile memory.
Why ROM is non-volatile?

6. PROM
• PROM stands for Programmable Read Only Memory.
• This form of ROM is initially blank. The user or manufacturer can
write data/program on it by using special devices.
• However, once the program or data is written in PROM chip, it
cannot be changed.
• If there is an error in writing instructions or data in PROM, the error
cannot be erased rather PROM chip becomes unusable.

7. EPROM
• EPROM stands for Erasable Programmable Read Only
Memory.
• This form of ROM is also initially blank.
• The user or manufacturer can write program or data on it by
using special devices.
• Unlike PROM, the data written in EPROM chip can be erased
by using special devices and ultraviolet rays.
• New data can also be added.
• When EPROM is in use, its contents can only be read.

8. EEPROM
• EEPROM stands for Electrically Erasable Programmable Read Only
Memory.
• This kind of ROM can be written or changed with the help of
electrical devices.
• So data stored in this type of ROM chip can be easily modified.

9. Flash Memory
• Flash memory is an electronic non-volatile computer storage medium
that can be electrically erased and reprogrammed. Introduced by
Toshiba in 1984, flash memory was developed from EEPROM
(electrically erasable programmable read-only memory).

10. END