Card readers (also known as card-acceptiong devices, CAD) perform fixed
operations like add, subtract or delete on memory cards.

Memory cards are usually used to provide secure access to computer and
phone networks.

Optical memory cards are useful to store relatively (compared to
microprocessor cards or memory cards) large amounts of data. They are
typically used to store data that rarely changes.

Optical memory cards are the best choice to perform cryptography
algorithms with their integrated 8-bit processor.

A microprocessor card has a processor and a small read-only memory as
well as a RAM.

For prepaid phone cards microprocessor cards are used most of the time.

Optical memory cards have an integrated LED.