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A PC Card, formerly a PCMCIA Card, is a peripheral interface device used with laptop computers that utilize the card port. Introduced in the early 1990s by the Personal Computer Memory Card International Association (PCMCIA), the slot was originally intended for memory card expansion. As technology evolved, many types of peripheral devices were available in the card format to add functionality to laptops. In 2003 the specification renamed the form factor and port to the ExpressCard slot.
The card is the size of a credit card with added thickness. The form factor varies between devices and port evolution. Cards use a 68-pin dual-row interface and are either 3.3-volt or 5-volt cards. The 3.3v cards have a protection feature that prevents them from being used in a 5v-only port. Some cards can work in either 3.3v or 5v mode. The PC Card falls into one of three categories: Type I, Type II or Type III.
Type I cards operate with a 16-bit interface, are 3mm thick, and were mainly used for RAM or flash memory expansion. A Type I card occupies a single PC Card slot, while most laptops of the day featured two slots or ports, one on top of the other.
Type II cards can be 16-bit or 32-bit and are 5mm thick. These cards provided in-and-out (I/O) support, introducing the ability to add functionality to the machine that was not originally built-in. Modems and network cards are two examples. The Type II card often includes a dongle, or short wire with a full size connector, made necessary due to the thinness of the card. The connector provides a jack for the necessary equipment, be it a phone line, Ethernet cable, or other interface.
Other Type II formats include an oversized or thick external end with the connector(s) built-in. While more convenient than a dongle, this form factor can block the secondary port. Still more variations feature retractable antennas and jacks to minimize bulkiness when the card is not in use, and to protect extending parts.
A Type III PC Card can also be 16-bit or 32-bit and is 10.5mm thick. These cards can accommodate connectors without the need of a dongle.
When a PC Card is inserted in a machine, the computer looks for the Card Information Structure (CIS) stored on the device. This data reveals the manufacturer, model, type of card, power requirements, options supported and other relevant information. If a machine does not recognize a card, one common reason is that the CIS file has become corrupted or is missing.
The card port made it possible to upgrade a laptop without opening it. If an internal component stopped working or became obsolete, a PC Card was the answer. From wireless modems to mobile broadband, from optical mice to TV cards, this interface kept laptops flexible and expandable.
With the introduction of the faster ExpressCard slot in 2003, the PC Card slot largely became legacy. By 2007 most laptops shipped only with the ExpressCard slot, or with no card slot out of deference to the growing trend of using USB ports to provide added functionality. In 2009 the PCMCIA disbanded, according to their website, turning over any further development to the USB Implementers Forum (USB-IF).