IOhandling

IO handling encompasses management of data transfers between a computer system and peripherals or other systems, including storage devices, networks, and human interfaces. It covers both reading and writing data and the policies and structures that enable these transfers. It sits between applications and hardware, and is implemented in kernels, libraries, and drivers.

Techniques include buffering and caching at multiple levels (application buffers, OS buffers, and disk caches) to smooth mismatches between producers and consumers. I/O modes include direct I/O, which bypasses user-space buffers, and buffered I/O. Memory-mapped I/O maps device memory into a process address space. File systems and device drivers translate high-level requests into device commands.

Synchrony and concurrency: synchronous I/O blocks the caller until completion, while asynchronous or non-blocking I/O allows operations to proceed in parallel. Event-driven models use polling, selectors (such as select, poll, or epoll/kqueue) or I/O completion mechanisms to notify completion. Devices interrupt to signal transfer status.

Performance and reliability: effective IO handling aims to maximize throughput and minimize latency, manage backpressure, and coordinate many concurrent requests. Error handling includes partial I/O recovery, retries, and robust reporting. Data integrity is protected by checksums, journaling, and transactional file systems.

Standards and scope: POSIX I/O provides portable interfaces for Unix-like systems; Windows offers Win32 I/O with overlapped operations. Some systems use virtual file systems to abstract hardware. IO handling design influences system architecture, including drivers, memory hierarchy, and application APIs.