PATHHardware Documentation > USB Devices > Mac OS USB DDK API Reference

Host Software

The client software, the USB management software, and the USB host controller together make up the host software in the USB logical topology.

The host plays a special role as the arbiter of all activity on the USB. A USB device can only gain access to the bus through the host by supplying a device descriptor that includes the information necessary to manage the device according to its features and class identifiers. See USB Services Library Reference for additional information about the contents of the device configuration descriptor structure.

The host interacts with USB devices through the host controller. The host is responsible for:

• Monitoring the attachment and removal of USB devices
• Managing control and data flow between the host and USB devices
• Maintaining device status and activity information
• Providing a limited amount of power to the USB

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