Modern network adapter hardware exists in several forms. Traditional Ethernet adapters for desktop PCs were PCI cards. PCMCIA (also know as "credit card" or "PC Card") adapters or similar devices that connected to USB ports were more commonly used in laptop computers. Nowadays, though, both Ethernet and wireless network adapters are simply integrated circuit chips pre-installed inside the computer.
Windows and other operating systems support both wired and wireless network adapters through a piece of software called a device driver. Network drivers allow application software to communicate with the adapter hardware. Network device drivers are often installed automatically when adapter hardware is first powered on.
Finally, some network adapters are purely software packages that simulate the functions of a network card. These so-called virtual adapters are especially common in virtual private networking (VPN) software systems.