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    <p>Consider using tables instead of <code>switch</code> statements. One column could be the transition criteria and another column is the destination state. </p> <p>This scales nicely because you don't have to change the table processing function; just add another row to the table.</p> <pre><code>+------------------+---------------------+---------------+ | Current state ID | transition criteria | Next state ID | +------------------+---------------------+---------------+ | | | | +------------------+---------------------+---------------+ </code></pre> <p>In my code at work, we use a column of function pointers rather than the "Next state ID". The table is a separate file with accessor functions defined. There is one or more include statements to resolve each function pointer.</p> <h2>Edit 1: Example of separate table files.</h2> <p><strong>table.h</strong></p> <pre><code>#ifndef TABLE_H #define TABLE_H struct Table_Entry { unsigned int current_state_id; unsigned char transition_letter; unsigned int next_state_id; }; Table_Entry const * table_begin(void); Table_Entry const * table_end(void); #endif // TABLE_H </code></pre> <p><strong>table.cpp:</strong> </p> <pre><code>#include "table.h" static const Table_Entry my_table[] = { // Current Transition Next // State ID Letter State ID { 0, 'A', 1}, // From 0 goto 1 if letter is 'A'. { 0, 'B', 2}, // From 0 goto 2 if letter is 'B'. { 0, 'C', 3}, // From 0 goto 3 if letter is 'C'. { 1, 'A', 1}, // From 1 goto 1 if letter is 'A'. { 1, 'B', 3}, // From 1 goto 3 if letter is 'B'. { 1, 'C', 0}, // From 1 goto 0 if letter is 'C'. }; static const unsigned int TABLE_SIZE = sizeof(my_table) / sizeof(my_table[0]); Table_Entry const * table_begin(void) { return &amp;my_table[0]; } Table_Entry const * table_end(void) { return &amp;my_table[TABLE_SIZE]; } </code></pre> <p><strong>state_machine.cpp</strong></p> <pre><code>#include "table.h" #include &lt;iostream&gt; using namespace std; // Because I'm lazy. void Execute_State_Machine(void) { unsigned int current_state = 0; while (1) { char transition_letter; cout &lt;&lt; "Current state: " &lt;&lt; current_state &lt;&lt; "\n"; cout &lt;&lt; "Enter transition letter: "; cin &gt;&gt; transition_letter; cin.ignore(1000, '\n'); /* Eat up the '\n' still in the input stream */ Table_Entry const * p_entry = table_begin(); Table_Entry const * const p_table_end = table_end(); bool state_found = false; while ((!state_found) &amp;&amp; (p_entry != p_table_end)) { if (p_entry-&gt;current_state_id == current_state) { if (p_entry-&gt;transition_letter == transition_letter) { cout &lt;&lt; "State found, transitioning" &lt;&lt; " from state " &lt;&lt; current_state &lt;&lt; ", to state " &lt;&lt; p_entry-&gt;next_state_id &lt;&lt; "\n"; current_state = p_entry-&gt;next_state_id; state_found = true; break; } } ++p_entry; } if (!state_found) { cerr &lt;&lt; "Transition letter not found, current state not changed.\n"; } } } </code></pre>
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    1. USThomas Matthews
    1. USThomas Matthews
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    1. COPlease could you give more details of how you are going to code this table in the separate file with accessor functions. If possible, by taking a small example state machine: 3 states(A, B, C); A(), B(), C() are the functions that have the operations needed to be done in each.
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    2. CO@Romonov: See new edited answer.
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