Question

how will you differentiate prom and a eprom
immediately please

Answer 1

Programmable read-only memory (PROM) is read-only memory ( ROM ) that can be modified once by a user. PROM is a way of allowing a user to tailor a microcode program using a special machine called a PROM programmer.

Computer memory types

Volatile

RAM

DRAM SRAM

Historical

Williams–Kilburn tube (1946–47) Delay line memory (1947) Mellon optical memory (1951) Selectron tube (1952) Dekatron T-RAM (2009) Z-RAM (2002–2010)

Non-volatile

ROM

Mask ROM PROM EPROM EEPROM Flash memory

NVRAM

ReRAM

Early stage NVRAM

FeRAM MRAM PCM

Magnetic

Magnetic tape Hard disk drive

Optical

Optical disc

In development

CBRAM Racetrack memory NRAM Millipede memory FJG RAM

Historical

Paper data storage (1725) Drum memory (1932) Magnetic-core memory (1949) Plated wire memory (1957) Core rope memory (1960s) Thin-film memory (1962) Disk pack (1962) Twistor memory (–1968) Bubble memory (–1970) Floppy disk (1971)

vte

STMicro M24C02 I²C serial type EEPROM

Atmel AT93C46A die

AT90USB162 MCU integrates 512 Byte EEPROM

A cross section of legacy UV-EPROM structure

Upper insulator: ONO†

Lower insulator: Tunnel oxide

†: Oxide/Nitride/Oxide

EEPROM (also E2PROM) stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers, integrated in microcontrollers for smart cards and remote keyless system, and other electronic devices to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed.

Answer 2

PROM-Programmable Read-Only Memory, is shipped from the factory with the possibility to write any kind of contents into the chip that you like … BUT it usually can only be done once. Typically, each bit of memory is stored with “fusible links,” and you “burn” the fuses to set that bit to a 1 or 0. PROM chips are usually “programmed” in a special device using high voltage, called a “programmer” or, more informally, a “burner.” They were an improvement on ROMs in that you could try out the program in small quantities before committing to a manufacturing run of ROMs, that has extensive setup involved, and wouldn’t be used EPROM-unless you want to make thousands of copies.
Electrically Erasable Programmable Read-Only Memory. That was an improvement over the earlier EPROMs because it no longer needed U-V light to erase the memory chip. Instead, you would just apply a special voltage to one of the pins on the chip, and voile! your chip is back to its empty state and can be programmed all over again. Why was that important? Because you no longer had to remove the chip from the board to put it into an eraser. Instead, you could add some circuitry on the board, and program and erase the memory over and over, still installed in the device where it belongs.