This is CNBC's Morning Squawk newsletter. Subscribe here to receive future editions in your inbox. Happy Tuesday. If Shakespeare were alive today reading about all these IPOs, he might've instead written: "To buy, or not to buy, that is the question." Stock futures are rising this morning after a mixed session. The S&P 500 rose modestly yesterday. Here are five key things investors need to know to start the trading day: Apple made a slew of announcements at its annual Worldwide Developers