State machine diagrams are a familiar technique to describe the behavior of a System. Various forms of State diagrams haue been around since the 1960s and the earliest object-oriented techniques adopted them to show behavior. In object-oriented approaches, you draw a State machine diagram for a single dass to show the lifetime behavior of a single object.<\/p>\n
Whenever people write about State machines, the examples are inevitably cruise controls or vending machines . As I’m a little bored wich them, 1 decided to use a controller for a secret panel in a Gothic castle . In this castle, 1 wanz to keep my valuables in a safe that’s hard to find . So to reveal the lock to the safe, 1 haue to remove a strategic candle from its holder, but this will reveal the lock only while the door is closed . Once 1 can See the lock, I can insert my key to open the safe . For extra safety, 1 make sure that 1 can open the safe only if 1 replaces the candle first . If a thief neglects this precaution, I’ll unleash a nasty monster to devour him.<\/p>\n
A\u00a0state diagram\u00a0is a type of\u00a0diagram<\/a>\u00a0used in\u00a0computer science<\/a>\u00a0and related fields to describe the behavior of systems. State diagrams require that the system described is composed of a finite number of\u00a0states<\/a>; sometimes, this is indeed the case, while at other times this is a reasonable\u00a0abstraction<\/a>. Many forms of state diagrams exist, which differ slightly and have different\u00a0semantics<\/a>.<\/p>\n State diagrams are used to give an abstract description of the\u00a0behavior<\/a>\u00a0of a\u00a0system<\/a>. This behavior is analyzed and represented by a series of events that can occur in one or more possible states. Hereby “each diagram usually represents objects of a single class and track the different states of its objects through the system”.<\/sup><\/p>\n State diagrams can be used to graphically represent\u00a0finite-state machines<\/a>\u00a0(also called finite automata). This was introduced by\u00a0Claude Shannon<\/a>\u00a0and\u00a0Warren Weaver<\/a>\u00a0in their 1949 book\u00a0The Mathematical Theory of Communication<\/i><\/a>. Another source is\u00a0Taylor Booth<\/a>\u00a0in his 1967 book\u00a0Sequential Machines and Automata Theory<\/i>. Another possible representation is the\u00a0state-transition table<\/a>.<\/p>\n A classic form of state diagram for a\u00a0finite automaton<\/a>\u00a0(FA) is a\u00a0directed graph<\/a>\u00a0with the following elements (Q, \u03a3, Z, \u03b4, q0<\/sub>, F):[2]<\/a><\/sup>[3]<\/a><\/sup><\/p>\n The output function \u03c9 represents the mapping of ordered pairs of input symbols and states onto output symbols, denoted mathematically as\u00a0\u03c9<\/b>\u00a0:\u00a0\u03a3<\/b>\u00a0\u00d7\u00a0Q<\/b>\u2192\u00a0Z<\/b>.<\/p>\n For a\u00a0deterministic finite automaton<\/a>\u00a0(DFA),\u00a0nondeterministic finite automaton<\/a>\u00a0(NFA),\u00a0generalized nondeterministic finite automaton<\/a>\u00a0(GNFA), or\u00a0Moore machine<\/a>, the input is denoted on each edge. For a\u00a0Mealy machine<\/a>, input and output are signified on each edge, separated with a slash “\/”: “1\/0” denotes the state change upon encountering the symbol “1” causing the symbol “0” to be output. For a\u00a0Moore machine<\/a>\u00a0the state’s output is usually written inside the state’s circle, also separated from the state’s designator with a slash “\/”. There are also variants that combine these two notations.<\/p>\n For example, if a state has a number of outputs (e.g. “a= motor counter-clockwise=1, b= caution light inactive=0”) the diagram should reflect this\u00a0: e.g. “q5\/1,0” designates state q5 with outputs a=1, b=0. This designator will be written inside the state’s circle.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":"Overview<\/span><\/h4>\n
Directed graph<\/span><\/h4>\n
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