Control flow

In <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, control flow (or flow of control) is the order in which individual <a href="/facts/Statement_(computer_science)/bEkBufqX">statements</a>, <a href="/facts/Instruction_(computer_science)/8p8vwUeE">instructions</a> or <a href="/facts/Function_call/9vFJrg0A">function calls</a> of an <a href="/facts/Imperative_programming/6b5dUnE1">imperative</a> <a href="/facts/Computer_program/e38jH9N9">program</a> are <a href="/facts/Execution_(computing)/1fyfGMFm">executed</a> or evaluated. The emphasis on explicit control flow distinguishes an <a href="/facts/Imperative_programming/6b5dUnE1">imperative programming</a> language from a <a href="/facts/Declarative_programming/gogtdzcJ">declarative programming</a> language.
Within an imperative <a href="/facts/Programming_language/cWTYbgWa">programming language</a>, a control flow statement is a statement that results in a choice being made as to which of two or more paths to follow. For <a href="/facts/Strict_programming_language/6zaxXvdQ">non-strict</a> functional languages, functions and <a href="/facts/Language_construct/4lDpHsIl">language constructs</a> exist to achieve the same result, but they are usually not termed control flow statements.
A set of statements is in turn generally structured as a <a href="/facts/Block_(programming)/E6yG3dnJ">block</a>, which in addition to grouping, also defines a <a href="/facts/Lexical_scope/bbj6AFMo">lexical scope</a>.
<a href="/facts/Interrupt/Mm6C4rpc">Interrupts</a> and <a href="/facts/Signal_(computing)/IN6VK6r8">signals</a> are low-level mechanisms that can alter the flow of control in a way similar to a <a href="/facts/Subroutine/9vFJrg0A">subroutine</a>, but usually occur as a response to some external stimulus or event (that can occur <a href="/facts/Asynchronous_systems/45LaDGdA">asynchronously</a>), rather than execution of an in-line control flow statement.
At the level of <a href="/facts/Machine_language/bgdQ1Fxf">machine language</a> or <a href="/facts/Assembly_language/7XuV0cla">assembly language</a>, control flow instructions usually work by altering the <a href="/facts/Program_counter/BxqulBRq">program counter</a>. For some <a href="/facts/Central_processing_unit/Jxp1bqMV">central processing units</a> (CPUs), the only control flow instructions available are conditional or unconditional <a href="/facts/Branch_(computer_science)/obBGrnor">branch</a> instructions, also termed jumps.

Control flow open-in-new

Control flow