Getting previous close high

Beginner Questions
1

To get the highest close value from the previous 20 bars, I assume the following code is ok?

int barIndex = iHighest (_Symbol, PERIOD_H1, MODE_CLOSE, 20, 0);
double highVal = iClose (_Symbol, PERIOD_H1, barIndex);
printf ("Highest value = " + highVal);

Thanks,
M.