Abstract: The present invention provides a PCMCIA-compliant generic laptop computer or personal digital assistant (“PDA”) device with an add-on module that together with the device forms a portable point of sale transaction terminal. The add-on module is a self-contained unit that includes a magnetic stripe reader or a smartcard reader with a PCMCIA-compatible interface. Optionally, the module also includes any or all of a pinpad unit, a printer unit, a fingerprint unit, a signature capture unit, and a virtual pinpad unit. The module housing includes a protruding snout-like member that includes a PCMCIA connector. This snout-like member on the module housing slides into the PCMCIA slot of the computer, PDA, or similar device to make mechanical and electrical connections. Software storable and executed by the computer or PDA device includes driver definitions and routines to permit the device to read and process information read by the module from the credit or smartcard.