Every online store uses a payment gateway application service provider that allows payment transaction to be possible in their shopping cart application. Most shopping carts come with the necessary payment gateway module to allow access to these third party services. Among the many Payment Gateway service providers are PayPal, Authorize.Net, Barclays EPDQ, National Bank, Pay Flow Link, Pay Flow Pro, Secure Hosting, and World Pay; just to name a few. These payment gateways provide merchant services are just like a physical point sale terminal, where secure transaction can be process by using credit cards, gift cards, banks account, etc.
For the programmer the challenge often comes when implementing the module using different Payment Gateway Application Programming Interface (API). Some Payment Gateway APIs often require the installation of drivers and dynamic Link Library (dll) files into the shopping cart hosting server which could create a problem of incompatibility. These problems often occurred due to different operating systems, or systems architecture instruction set incompatibility.