State machines are very simple in C if you use function pointers.

statemachine.c

/*
http://stackoverflow.com/questions/1371460/state-machines-tutorials/1371654#1371654

State machines are very simple in C if you use function pointers.

Basically you need 2 arrays - one for state function pointers and one for state 
transition rules. Every state function returns the code, you lookup state 
transition table by state and return code to find the next state and then 
just execute it.
*/

int entry_state(void);
int foo_state(void);
int bar_state(void);
int exit_state(void);

/* array and enum below must be in sync! */
int (* state)(void)[] = { entry_state, foo_state, bar_state, exit_state};
enum state_codes { entry, foo, bar, end};

enum ret_codes { ok, fail, repeat};
struct transition {
    enum state_codes src_state;
    enum ret_codes   ret_code;
    enum state_codes dst_state;
};
/* transitions from end state aren't needed */
struct transition state_transitions[] = {
    {entry, ok,     foo},
    {entry, fail,   end},
    {foo,   ok,     bar},
    {foo,   fail,   end},
    {foo,   repeat, foo},
    {bar,   ok,     end},
    {bar,   fail,   end},
    {bar,   repeat, foo}};

#define EXIT_STATE end
#define ENTRY_STATE entry

int main(int argc, char *argv[]) {
    enum state_codes cur_state = ENTRY_STATE;
    enum ret_codes rc;
    int (* state_fun)(void);

    for (;;) {
        state_fun = state[cur_state];
        rc = state_fun();
        if (EXIT_STATE == cur_state)
            break;
        cur_state = lookup_transitions(cur_state, rc);
    }

    return EXIT_SUCCESS;
}

/*
I don't put lookup_transition() function as it is trivial.

That's the way I do state machines for years.
*/

i have a question regarding the data exchange between the action functions (i.e. entry_state and foo_state) if some data is processed in entry_state and that data is needed in foo_state, than the only way to do this are the global variables, and in my Point of view this is not the optimal way of programming. Please correct me if i missed something or missunderstood. If it is so, what is your aproach of exchange data between these functions, avoiding the global variables?

I have aquestion how ican make position gearangles put it into statemachine aftershutdown back start given thesame position without miss the position or please give me solution if you know this imade the control of camshaft
int pulse=0;
char text[15];
void main() {
TRISD.F0 = 1;
TRISA=0X00;
PORTA=0;
TRISC=0X00;
PORTC=0;
#define SW PORTD.RD0 // RD7 pin is pulse input pin
while(1){
if(SW==1){
while(SW==1);
pulse++;
}
if(pulse>=721) pulse = 0;
if(RD0_bit==1) pulse ++;
if(pulse== pulse <=128){

             portc.f5=0;

             }
             if (pulse>= 129 && pulse <=180){
             porta.f2=1;

             }
             if (pulse>=181&& pulse <=308){
             porta.f2=0;
             portc.f3=0;
             portc.f4=0 ;
              }
             if (pulse>=309 && pulse <=360){
             porta.f2=0;
              portc.f3=1 ;
             portc.f4=0;
             portc.f5=0;

             }if (pulse>=361 && pulse <=488){
             porta.f2=0;
              portc.f3=0 ;
             portc.f4=0;
             portc.f5=0;

             }
            if (pulse>=489 && pulse <=540){
             porta.f2=0;
              portc.f3=0 ;
             portc.f4=1;
             portc.f5=0;

             }
           if (pulse>=541 && pulse <=668){
             porta.f2=0;
              portc.f3=0 ;
             portc.f4=0;
             portc.f5=0;

             }
         if (pulse>=669 && pulse <=720){
             porta.f2=0;
              portc.f3=0;
             portc.f4=0;
             portc.f5=1;

             }

}
}

Hey everybody, I just saw all of your questions regarding this gist for the first time - sorry for being late to reply. I did not author this code, please see the link to the stackoverflow post in the first line. The original author can be asked there.