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The two main jobs of a computer are input/output (I/O) and processing. The role of the operating system in computer I/O is to manage and control I/O operations and I/O devices.

Computers operate a great many kinds of devices. Most fit into the general categories of storage devices, transmission devices, and human-interface devices. Despite the incredible variety of I/O devices, we need only a few concepts to understand how the devices are attached and how the software can control the hardware.

• Pertaining to I/O hardware at a minimum, your response should address the following:
  • The main concepts pertaining to how the devices are attached and how the software can control hardware
  • Relevant points, including definitions of the following:
    • Buses, especially a PCI bus
    • Controllers
    • I/O port registers
    • Polling
    • Interrupts
    • Direct memory access