State Machine with Enums

Question

Problem: State Machine with Enums. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 
#include 
using namespace std;

enum class State { Idle, Busy, Error };

const char* toString(State s) {
    switch (s) {
        case State::Idle:  return "Idle";
        case State::Busy:  return "Busy";
        case State::Error: return "Error";
    }
    return "";
}

int main() {
    int n;
    cin >> n;

    State state = State::Idle;

    for (int i = 0; i < n; ++i) {
        string cmd;
        cin >> cmd;

        if (state == State::Error) {
            continue; // ignore all commands after Error
        }

        if (cmd == "start" && state == State::Idle) {
            state = State::Busy;
        } else if (cmd == "done" && state == State::Busy) {
            state = State::Idle;
        } else if (cmd == "fail" && state == State::Busy) {
            state = State::Error;
        }
    }

    cout << toString(state);
    return 0;
}

Explanation & Logic Summary

State is an enum representing the finite states of the system.
The system starts in Idle.
Commands trigger transitions only when valid for the current state.
Invalid transitions are ignored.
Once Error is reached, the system remains in Error.
The final state is printed using toString(State).

Firmware Relevance & Real Embedded Meaning

Finite State Machines (FSMs) are fundamental in embedded systems (drivers, protocols, task schedulers).
enum class provides type safety and readability over raw integers.
Explicit state transitions improve reliability, debuggability, and maintainability in firmware code.

60. State Machine with Enums