1968 Science Advertisement for the HP 9100A. Copyright by and used with permission of Hewlett-Packard

1. The Machine That Made Silicon Valley

When Hewlett-Packard got into the personal computer business, a “personal computer” was a $4900 calculator. Ads for HP’s 9100A aimed at scientists and engineers in 1968 called it by different names: an electronic genie, a computing marvel and yes, a personal computer.

The 9100A used mathematical notation rather than software code. It fit on a desk, and almost anyone could use it. It was a fairly capable general programming machine, but to reach a broader...

A new feature lets you turn Google's social service into a YouTube music party.

Listen up, music fans: Thanks to a recently launched feature in the Google+ social network, members can set up listening rooms where friends — or complete strangers — can listen to music together and chat about it.

If you thought embedding YouTube videos on Facebook was neat, just wait until you see how Google+ lets people throw group listening parties. To...