Subroutine

A subroutine is a reusable sequence of instructions that performs a defined task within a program. It can be invoked from other parts of the program, often with inputs and outputs.

Subroutine call: A control-flow operation that transfers execution to a subroutine and resumes at the call site when it returns. A call starts the subroutine and determines where execution continues afterward.
Control flow: The order in which a program's instructions are executed, including branches, loops, and calls. Subroutine calls are one way a program changes its ordinary instruction sequence.
FORTRAN: A programming language introduced in the 1950s for scientific and engineering computation. FORTRAN helped establish named subprograms as reusable units in compiled languages.
Application programming interface: A defined interface through which software components request services from one another. Library subroutines are often exposed through an API that specifies how programs call them.
Inline expansion: A compiler optimization that replaces a call with the called code at the call site. Inlining removes the runtime call boundary that ordinary subroutine reuse retains.
Parameter (computer programming): A named input variable in a function or subroutine definition. Parameters let one subroutine perform its task on different supplied values.
Procedure (computer science): A named block of code that performs an operation and may not return a value. In many languages, procedure is the closest term for a subroutine without a result.
COBOL: A programming language designed for business data processing and standardized in 1960. COBOL's PERFORM statement made paragraph- and section-level routines central to program structure.
Standard library: A collection of commonly needed routines and data types distributed with a programming language implementation. Standard libraries let programs reuse subroutines for tasks such as input, output, and mathematics.
Macro (computer science): A rule that transforms source code before or during compilation, often by substituting code at a use site. A macro can resemble a subroutine call but expands code rather than invoking a runtime routine.

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