Overlapped IO

lastmod 2026-11-10created 2014-05-132 edits

Overlapped I/O is an asynchronous I/O method on Windows that lets a program issue an I/O request and keep doing other work without waiting for it to complete. You open a file or socket with FILE_FLAG_OVERLAPPED and pass an OVERLAPPED structure with the request; completion is notified through an event, a callback, or IOCP. It is commonly used together with IOCP in high-performance servers.