PCMCIA

Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. There are in fact three types of PCMCIA cards. All three have the same rectangular size (85.6 by 54 millimeters), but different widths
Type I cards can be up to 3.3 mm thick, and are used primarily for adding additional ROM or RAM to a computer.

Type II cards can be up to 5.5 mm thick. These cards are often used for modem and fax modem cards.

Type III cards can be up to 10.5 mm thick, which is sufficiently large for portable disk drives.

As with the cards, PCMCIA slots also come in three sizes:
A Type I slot can hold one Type I card

A Type II slot can hold one Type II card or one Type I card

A Type III slot can hold one Type III card or any combination of two Type I or II cards.

In general, you can exchange PC Cards on the fly, without rebooting your computer. For example, you can slip in a fax modem card when you want to send a faxand then, when you’re done, replace the fax modem card with a memory card.