40. State Machine Using Function Pointers

#include <stdio.h>

void state_init()    { printf("Init"); }
void state_load()    { printf("Load"); }
void state_execute() { printf("Execute"); }
void state_exit()    { printf("Exit"); }

void run_state_sequence(int start) {
    // Function pointer array for 4 states
    void (*fsm[4])() = { state_init, state_load, state_execute, state_exit };

    // Execute 3 states in sequence starting from 'start'
    for (int i = 0; i < 3; i++) {
        int index = (start + i) % 4;  // Wrap around with modulo
        fsm[index]();
        if(i < 2){
            printf("\n");
        }
    }
}

int main() {
    int start;
    scanf("%d", &start);
    run_state_sequence(start);
    return 0;
}

• A function pointer array fsm[] maps an index to state functions
• A loop calls the next 3 states using (start + i) % 4
• Clean, extensible state machine logic

✅ This pattern is widely used in firmware state machines, command handlers, and timed sequences.