The day after the iPhone 4S announcement, at about 5 p.m. Pacific time, the tech world suffered an immeasurable loss in the death of Apple co-founder Steve Jobs. The 56-year-old died at home after a long fight with pancreatic cancer. Some reactions follow:

President Barack Obama: ”Steve’s brilliance, passion and energy were the source of countless innovations that enrich and improve all of our lives. The world is immeasurably better because of Steve.” [via WhiteHouse.gov]

Facebook founder Mark Zuckerberg: “Steve, thank you for being a mentor and a friend. Thanks for showing that what you build can change the world. I will miss you.” [via Facebook]

Microsoft CEO Steve Ballmer: “I want to express my deepest condolences at the passing of Steve Jobs, one of the founders of our industry and a true visionary. My heart goes out to his family, everyone at Apple and everyone who has been touched by his work.” [via Microsoft.com]