Scott McNealy, a co-founder of Sun Microsystems Inc. (SUNW), said Monday he will step down immediately as chief executive of the company he has led since 1984.

Jonathan Schwartz, the company's president, will retain that position and take over as chief executive, executives said on a conference call to announce third-quarter earnings.

McNealy, whose vision of large, networked computers helped shape today's Internet, will remain as Sun's chairman.

McNealy, 51, co-founded Santa Clara-based Sun Microsystems in 1982, leading it from a Silicon Valley startup to a leading provider of network computing infrastructure with nearly 40,000 employees worldwide, according to the company's Web site.