The Personal Computer Memory Card International Association, or PCMCIA, slot is used to connect hardware interfaces that are similar in size to a credit card, with the exception of corner rounding and thickness. These hardware interfaces are widely referred to as PC cards.
The PCMCIA standard was initially designed to add memory to laptop computers. However, the PCMCIA standard has since been expanded to add functionality to portable computers by making devices such as modems and network cards that are based on the PC card form factor. PCMCIA cards have three different dimensions. They all have a similar rectangular size, such as 54 millimeters by 85.6 millimeters, but with varying widths. Type I is 3.3 millimeters thick, Type II is 5 millimeters thick, and Type III is 10.5 millimeters thick.