We offenly read the news that " Fresh Call writing was seen at strike prices 7,700 (2.4 lakh contracts added), 7,800 (7.7 lakh contracts added) and 7,900 (3.2 lakh contracts added), which will act as key resistance levels for traders.
How to find out which strike call /put writing has been done and is it possible to findout in Trading Hours ?
Check this link on NSE for option chain. You can track OI on this page live for all strikes. You can look at the change in OI column.
OI or open interest adding means, new contracts getting added. When OI gets added, it means both new buyers and writers of options are coming in, but the logic is option writers are the smarter lot, so whatever strike they are writing would act as a resistance/support.
Check this chapter on Max Pain on Varsity.