Type

Volatile?

Write able?

Erase Size

Max Erase Cycles

Cost (per Byte)

Speed

SRAM

Yes

Yes

Byte

Unlimited

Expensive

Fast

DRAM

Yes

Yes

Byte

Unlimited

Moderate

Moderate

Masked ROM

No

No

n/a

n/a

Inexpensive

Fast

PROM

No

Once, with a device programmer

n/a

n/a

Moderate

Fast

EPROM

No

Yes, with a device programmer

Entire Chip

Limited (consult datasheet)

Moderate

Fast

EEPROM

No

Yes

Byte

Limited (consult datasheet)

Expensive

Fast to read, slow to erase/write

Flash

No

Yes

Sector

Limited (consult datasheet)

Moderate

Fast to read, slow to erase/write

NVRAM

No

Yes

Byte

Unlimited

Expensive (SRAM + battery)

Fast