Columbia Journalism School, founded a century ago to train generations of reporters, was only 7 years old when Pittsburgh’s KDKA made the first broadcast by a licensed radio station. Now the digital revolution is upending the practice of journalism.

Newspapers and magazines are vanishing amid deep cutbacks and an inexorable march onto virtual platforms. Broadcast media struggle as cable networks and the Web aim at ever narrower audiences. And with social media, anyone can set up a media enterprise and join the fray.