functioncall

A function call is the act of invoking a function or method in a program. It transfers execution from the caller to the called function, supplies arguments, and, typically, returns a value to the caller. A function call may also be described as applying a function to a set of inputs.

When a call occurs, the language usually creates a new activation frame on the call stack to hold the function’s parameters, local variables, and the return address. The arguments are evaluated (according to the language’s rules) and bound to the function’s parameters, after which the function body is executed. When the function completes, its return value is handed back to the caller and control resumes at the point after the call. Calls can produce side effects, such as modifying global state or I/O.

Key concepts related to function calls include parameter passing mechanisms (such as pass-by-value, pass-by-reference, and pass-by-sharing), default and variadic arguments, and the order in which arguments are evaluated. Some languages guarantee a specific evaluation order, while others leave order unspecified.

Return values and side effects are central to the semantics of a call. A function may return a value, perform actions without returning a value (a procedure), or raise an exception on error. Calls are fundamental to programming in all paradigms and support patterns such as recursion and higher-order functions, where functions are passed as arguments or returned as results.

Optimizations may affect function calls, including inlining small calls or applying tail call optimization to reuse stack frames in certain languages. The details of function calling conventions vary by language and runtime but the basic model—evaluate arguments, transfer control, and obtain a result—remains common.