What is the purpose of an adapter card in a computer system?

The purpose of an adapter card in a computer system primarily revolves around enabling communication between the central processing unit (CPU) and various external devices. Adapter cards serve as interfaces that translate signals and data between the computer's internal components and the peripherals connected to it, such as printers, external storage, and network devices.

For example, a network interface card (NIC) allows the computer to connect to a network, while a sound card facilitates audio output and input. By allowing the CPU to communicate effectively with these devices, adapter cards play a crucial role in expanding the functionality of a computer system, ensuring that various external components can work optimally with the central processing unit.

The other options pertain to functions that are not the primary role of adapter cards. Increasing hard drive storage capacity is typically related to the acquisition of storage hardware rather than an adapter card; upgrading the operating system is a software function that is controlled by the computer's memory and storage, and enhancing display quality is specifically related to graphics cards, which are a subset of adapter cards but serve a different and more specialized function compared to broader communication needs.