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Control flow
In software, control flow (or flow of control) describes how execution progresses from one command to the next. In many contexts, such as machine code and an imperative programming language, control progresses sequentially (to the command located immediately after the currently executing command) except when a command transfers control to another point – in which case the command is classified as a control flow command. Depending on context, other terms are used instead of command. For example, in machine code, the typical term is instruction and in an imperative language, the typical term is statement.
Although an imperative language encodes control flow explicitly, languages of other programming paradigms are less focused on control flow. A declarative language specifies desired results without prescribing an order of operations. A functional language uses both language constructs and functions to control flow even though they are usually not called control flow statements.
For a central processing unit (CPU) instruction set, a control flow instruction often alters the program counter and is either an unconditional branch (a.k.a. jump) or a conditional branch. An alternative approach is predication which conditionally enables instructions instead of branching.
An asynchronous control flow transfer such as an interrupt or a signal alters the normal flow of control to a hander before returning control to where it was interrupted.
One way to attack software is to redirect the flow of execution. A variety of control-flow integrity techniques, including stack canaries, buffer overflow protection, shadow stacks, and vtable pointer verification, are used to defend against these attacks.
Control flow is closely related to code structure. Control flows along lines defined by structure and the execution rules of a language. This general concept of structure is not be confused with structured programming which limits structure to sequencing, selection and iteration based on block organization.
Sequential execution is the most basic structure. Although not all code is sequential in nature, imperative code is.
A label identifies a position in source code. Some control flow statements reference a label so that control jumps to the labeled line. Other than marking a position, a label has no other effect.
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Control flow AI simulator
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Control flow
In software, control flow (or flow of control) describes how execution progresses from one command to the next. In many contexts, such as machine code and an imperative programming language, control progresses sequentially (to the command located immediately after the currently executing command) except when a command transfers control to another point – in which case the command is classified as a control flow command. Depending on context, other terms are used instead of command. For example, in machine code, the typical term is instruction and in an imperative language, the typical term is statement.
Although an imperative language encodes control flow explicitly, languages of other programming paradigms are less focused on control flow. A declarative language specifies desired results without prescribing an order of operations. A functional language uses both language constructs and functions to control flow even though they are usually not called control flow statements.
For a central processing unit (CPU) instruction set, a control flow instruction often alters the program counter and is either an unconditional branch (a.k.a. jump) or a conditional branch. An alternative approach is predication which conditionally enables instructions instead of branching.
An asynchronous control flow transfer such as an interrupt or a signal alters the normal flow of control to a hander before returning control to where it was interrupted.
One way to attack software is to redirect the flow of execution. A variety of control-flow integrity techniques, including stack canaries, buffer overflow protection, shadow stacks, and vtable pointer verification, are used to defend against these attacks.
Control flow is closely related to code structure. Control flows along lines defined by structure and the execution rules of a language. This general concept of structure is not be confused with structured programming which limits structure to sequencing, selection and iteration based on block organization.
Sequential execution is the most basic structure. Although not all code is sequential in nature, imperative code is.
A label identifies a position in source code. Some control flow statements reference a label so that control jumps to the labeled line. Other than marking a position, a label has no other effect.