This is the VOA Special English Economics Report.

Changes are taking place in Silicon Valley in California. Larry Page will replace Eric Schmidt as chief executive at Google. And Apple's chief, Steve Jobs, is taking another medical leave.

Two years ago Mr. Jobs received a new liver. In two thousand four he had pancreatic cancer. This month's announcement did not say how long he might be away or give a reason.

Apple reported record-high earnings for the final three months of last year. But the health of Steve Jobs always brings questions about the future of the company.

He helped start Apple Computer in nineteen seventy-six. Today the company that played a big part in the personal computing revolution just calls itself Apple. Its products include the iPod and iPhone, and it expects to sell six million iPad tablet computers this year.

Steve Jobs has long been Apple's public face. But some might forget that he left in nineteen eighty-five to form a computer company called NeXT.

Manuel Perez-Quinones is a computer science professor at Virginia Tech. He says Apple has led the development of some technologies, but that explains only part of its success.

MANUEL PEREZ-QUINONES: "Apple has been a driver in some things and they have been a faithful adopter of good ideas in others."

For example, he says many development tools associated today with Apple came from NeXT.

MANUEL PEREZ-QUINONES: "The development environment, the programming languages, some of the libraries that are used were things that Steve Jobs was very tightly connected to from the very beginning. But it was not necessarily at Apple. It came from NeXT Computer."

Apple bought NeXT in nineteen ninety-six. Mr. Jobs rejoined Apple and became the permanent CEO in two thousand.

Last May, Apple passed Microsoft in market value and became the most valuable technology company in the world.

Mr. Jobs says he will remain chief executive officer and stay involved in major decisions during his medical leave. But he put Tim Cook, his chief operating officer, in control of daily operations.

As Steve Jobs steps back at Apple, Eric Schmidt is stepping down at Google. Mr. Schmidt plans to leave his CEO job in April after almost ten years. He will remain on Google's board of directors.

Larry Page was Google's founding CEO when he launched the company with Sergey Brin in nineteen ninety-eight. But Mr. Schmidt has been the public face of Google while Mr. Page has mainly worked on new products.

Today Google is the world leader in Internet search and has products like the Android operating system for mobile devices. But Google is seen as trying to recapture the creative energy and speed of its early days.

And that's the VOA Special English Economics Report, written by Mario Ritter. I'm Steve Ember.