Here we look at a 3C response to 1NT used as 5-card Stayman. I nice modern addition to your bidding system. This in combination with a 2C Stayman response created an effective system for communication.
When we open a NT and partner uses an artificial conventional responses, like Stayman or Transfers, then the opponents might double as lead directing. We want to use this double against them. Here we discuss our options for bidding after this double.