This slide reviews the classifications of semiconductor memory. IC memory can roughly be divided into two categories; the first is Random Access Memory or RAM, the second is Read-Only Memory, known as ROM. RAM can be read and written anytime but the memory will be erased once the power supply is turned off. On the other hand, ROM is either written slower than RAM, or it cannot be written at all. In addition, ROM can maintain its memory even if the power supply is turned off. Therefore ROM is useful for read-only solutions where the memory does not always have access to power.