This is a simple program to blink LED on a cheap MCU (think Arduino), to be fixed:

int main()
{
    int led_port=...;
    int led_state=0;
    while(1)
    {
        led_state = ???; // fill the right part of expression
        out_port(led_port, led_state); // send 0, 1, 0, 1 ...
        sleep(for some time);
    };
};

Do not add any more lines to code, just fill the right part of aforementioned
expression.
(It may be long, not just three characters.)