8 Input and Output Management Free Online FlashCards

What does operating-system I/O management do?

It coordinates communication between programs and hardware, routing requests, managing buffers and access permissions, and reporting results.

How does a typical I/O request travel from a program to a device?

An application makes a request to the OS, the I/O subsystem routes it to a device driver, and the device performs the operation. The OS then makes the result available to the program.

What is a device driver’s main role?

A device driver lets the OS operate a particular device or class of devices by translating general requests into device-specific commands.

What are device registers used for?

They are small control and status locations that a driver can use to issue commands to a device or check its state.

What is memory-mapped I/O (MMIO)?

Memory-mapped I/O uses a region of address space to access a device’s registers.

How does direct memory access (DMA) help with large transfers?

DMA transfers data between a device and main memory without requiring the CPU to copy each byte. The OS and driver arrange the transfer and handle its completion.

What is polling, and what is one drawback?

Polling is when the CPU repeatedly checks a device’s status. It is straightforward, but the repeated checks use processing time even when the device has nothing to report.

What happens when a device raises an interrupt?

An interrupt is a signal from a device that it needs attention, such as when input arrives or a transfer finishes. The processor handles the event, then resumes other work.

What should an interrupt handler do first?

It performs the time-sensitive work needed to acknowledge or identify the event. Longer processing can be deferred so the immediate response stays short.

What must a handler check when devices share an interrupt?

A handler may need to check whether its own device caused the interrupt before responding.

What is a buffer in I/O management?

A buffer is temporary memory that holds data while it moves between a program and a device.

Why can buffers help when programs and devices transfer data?

Buffers accommodate differences in transfer speed and size, such as gradual keyboard input being collected for a program that processes larger chunks.