Käsitlejate

Käsitlejate is a term used in Estonian computing terminology to describe software components or functions designated to handle a specific type of input, event, or data. In programming, a handler is activated when the associated event occurs or when data arrives. They are common in event-driven and asynchronous environments, where control flow is driven by interactions rather than a linear sequence.

Common types include event handlers, exception handlers, and I/O handlers. Event handlers are registered with an event source and invoked when the event occurs; they may follow callback, listener, or observer patterns. Exception handlers catch and process errors or exceptional conditions to maintain program stability. I/O handlers mediate input and output, managing data flow, buffering, and readiness states.

In many languages and frameworks, handlers are first-class entities, passed as functions or objects and attached to specific events, signals, or resources. Design considerations for handlers include proper scoping and lifetime management, avoiding tight coupling, ensuring reentrancy and thread safety, and handling errors without destabilizing the system. Performance concerns include minimizing allocation in hot paths and reducing dispatch overhead.

Examples of handlers in practice include a graphical user interface button’s click handler, a web server’s request handler, or a filesystem watcher that reacts to file changes. The term is widely used across programming languages, and in Estonian documentation “käsitleja” and plural “käsitlejad” are common for such constructs.

Etymology-wise, the word derives from the Estonian verb käsitlema, meaning to handle or process, with käsitleja meaning a handler or processor.