The internal components of these types of computers have a varying amount of capacity and power. However, all computers, from PDAs to mainframes, include the same basic components. A CPU processes information; the amount of work it can do depends on its clock speed and bandwidth. The I/O bus transfers data between input components, output devices, the CPU, memory, and other internal computer components. Like the CPU, there are a variety of I/O bus types, each with its own performance characteristics. Computer memory ranges from volatile RAM to various types of nonvolatile ROM.

To physically connect to a network, a computer must be equipped with a NIC. Each type of network cable connection requires a different type of NIC. The performance of a NIC depends on the performance of the computer's other components.

The computer hardware is controlled by the OS software and device drivers. An OS is a suite of software that manages applications, user interfaces, storage, and internal and external components. The OS provides many low-level services, such as reading and writing to disks, handling I/O, and assigning memory and processing time to multiple applications. Device drivers are like small OS modules that control internal and external accessories, such as disk drives, network connections, and printers.

Microsoft Windows is the dominant OS for desktop PCs. However, NOSs such as Novell NetWare, UNIX, and Linux are also common on larger systems, such as workstations, servers, mid-range computers, and mainframes.

Application software is what a user sees and works with; applications are tools that help a user to be productive. The application software uses the underlying OS to perform low-level functions, such as file access and management. Some of the most common types of applications include word processors, spreadsheets, databases, games, and Web browsers. Some applications are designed for one user at a time, while others are made to support multiple simultaneous users on a network.

Network management and utility software is considered a distinct category of software, separate from user applications. This software is used by network and system administrators for managing and accessing network or computer OSs. Network management tools help keep a network healthy by monitoring data traffic flow, managing storage backup and recovery, providing remote network access, and preventing or eliminating viruses.

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