switch and if statement order (Robot C)

I'm writing practice finite state machine code and can't wrap my head around the order of my "Switch" and "if" statements (which should come first).

Currently, I have it written as such:

task main()
{
    // State variable default.
    SystemStateType SystemState = State1;

    While(1)
    {
        //Taken in from external sensors in real time
        int reading;

        if (reading == 0)
        {
            SystemState = State1;
        }
        else
        {
            SystemState = State2;
        }

        switch (SystemState)
        {
            case State1:
                //actions
                break;

            case State2:
                //other actions 
                break;
        }
    }
}

The code is intended to take sensor data in real time and respond accordingly. I realize that this is not actual functioning code, but I'm hoping that since the question is theoretical that my current code shown will suffice. Please let me know if I am missing anything.

Thank you!

can't wrap my head around the order of my "Switch" and "if" statements (which should come first).

Your switch statement examines the value of the SystemState variable, which is set through your if statement. So the correct order is to have your if statement, so that SystemStatevariable takes the desired value, and then examine the value of SystemState in your switch statement.

Suppose that you had if and switch statements the opposite way, like this :

task main()
{
    // State variable default.
    SystemStateType SystemState = State1;

    While(1)
    {
        //Taken in from external sensors in real time
        int reading;

        switch (SystemState)
        {
            case State1:
                //actions
                break;

            case State2:
                //other actions 
                break;
        }

        if (reading == 0)
        {
            SystemState = State1;
        }
        else
        {
            SystemState = State2;
        }

    }
}

Then, in the switch statement your SystemState variable would always be State1.

Of course, keep in mind that in the way you have written your code right now, reading cannot receive any input. You need to give reading a way to get a value.