BY: Vivek Jariwala

MEMORY

Memory refer to computer components, devices and recor

ding media that hold digital data and program.

Memory usually refers to a form of solid state storage known

as random access memory (RAM) or read only memory (RO

M)

STORAGE

Storage more commonly refers to mass storage - optical

discs, forms of magnetic storage like hard disks, and other

types of storage which are slower than RAM , but can hold

data permanently.

WHAT IS “ROM”?

?"R0M"

It works as a storage medium, used in computers and other

electronic devices.

Data stored in this memory cannot be modified. so it is

mainly used to distribute software that is very closely tied to

specific hardware, and unlikely to need frequent updates.

It usually refers only to mask ROM (oldest type of ROM),

which is fabricated with the desired data permanently stored

in it, and can never be modified.

?"ROM"

According to Wikipedia; “Classic ROM chips are integrated

circuits that store data physically, so that it is impossible to

change their contents after fabrication. Other types of non-

volatile memory allow some degree of modification.”

USES AND CHARACTERISITCS OF ROM

ROM usually stores the startup instructions for the

computer, and it also helps to load the operating system.

Now, regarding reading and writing speeds;

For those types of ROM that can be electrically modified, writing speed is

always much slower than reading speed, and it may need unusually high

voltage. Modern Flash devices achieve the highest write speeds of any

rewritable ROM technology, with speeds as high as 15 MB/s(or 70

ns/bit), by allowing large blocks of memory cells to be written

simultaneously.

TYPES OF "ROM"

PROM

Programmable read-only memory (PROM), or one-time programmable

ROM (OTP), can be written to or programmed. Typically, this device

uses high voltages to permanently destroy or create internal links within

the chip. Consequently, a PROM can only be programmed once.

EPROM

Erasable programmable read-only memory (EPROM) can be

erased by exposure to strong ultraviolet light (typically for 10

minutes or longer), then rewritten with a process that again

needs higher than usual voltage applied. Repeated exposure

to UV light will eventually wear out an EPROM, but the

endurance of most EPROM chips exceeds 1000 cycles of

erasing and reprogramming.

EPROM chip packages can often be identified by the

prominent quartz "window" which allows UV light to enter.

After programming, the window is typically covered with a

label to prevent accidental erasure. Some EPROM chips are

factory-erased before they are packaged, and include no

window.

EEPROM

• Electrically erasable programmable read-only memory

(EEPROM) is based on a similar semiconductor structure to

EPROM, but allows its entire contents to be electrically

erased or rewritten, so that they don’t need to be removed

from the computer or device. Writing or flashing an

EEPROM is much slower than reading from a ROM or

writing to a RAM.

EAROM FLASH

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