(FORTUNE Magazine) – Just to reach their centennials -- which Coca-Cola, Olin, and others do this year -- companies have had to endure 23 recessions, the Great Depression, six wars, innumerable changes in the tax code, 19 Presidents, and, not least, the merger mania of the 1980s. General Electric turns 100 on April 15. It not only has survived (see table for highlights) but is looking youthfully exuberant. University of Michigan business professor Noel Tichy, who is writing a book on GE, says although it is best known for medical technology and a variety of products like refrigerators, its continued contribution to management concepts is what assures GE its place in the corporate hall of fame. Not all those ideas were good. GE added layers of bureaucracy from the 1950s through the 1970s. By 1980 it was losing domestic market share in core businesses such as light bulbs. It neglected foreign markets and entered unprofitable areas like nuclear reactors. In 1981, Jack Welch took over. He has divested 289 lackluster businesses such as consumer electronics, raising $10 billion, and spent $19 billion on what he hoped would be better ones, including Kidder Peabody. In the past decade, Welch, now 56, has tried to infuse the company with a sense of entrepreneurship, and in doing so has become one of the country's most admired CEOs. But the rest of his watch could be much tougher. Says Tichy: ''Welch is a little past half time. The question is, Can he embed the values of speed, simplicity, openness, and candor throughout such a large company?'' Lots of GE operations need a jolt. Some, including power and medical systems, are flourishing. But the recession has hurt plastics and aircraft engines. NBC is often rumored to be for sale. Says Paine Webber security analyst Mark Altman: ''GE is an opportunistic company, and I wouldn't rule anything out.''

CHART: NOT AVAILABLE CREDIT: FORTUNE CHART CAPTION: GENERAL ELECTRIC AT 100: STILL IN A STATE OF CHANGE