SAN FRANCISCO — Timothy D. Cook, Apple’s chief executive, likes to tell people that his predecessor, Steven P. Jobs, urged him to be himself when he took over the company.

Mr. Cook is taking that advice. On Thursday, he said he was gay — the most striking example of how he is in many ways making Apple a more open, less secretive company.

“Let me be clear: I’m proud to be gay, and I consider being gay among the greatest gifts God has given me,” Mr. Cook wrote in the essay, published by Bloomberg Businessweek.

Mr. Cook’s decision is unlikely to have any major impact on Apple’s global business, said business analysts and professors. But they added that because it was a bold move, it was full of unknowns. No business executive of Mr. Cook’s stature has ever done something like this before. And while laws legalizing same-sex marriage are sweeping places like the United States, Latin America and Europe, gay rights advocates are still struggling to secure basic protections in Asia, where Apple generated 27 percent of its revenue in the fourth quarter.