NEW YORK, MAY 29 -- A late burst of computerized buy-programs, fed by optimism about the upcoming Soviet-U.S. summit and a renewed interest in high-technology stocks, sent the Dow Jones industrial average soaring nearly 50 points today to a record close.

Broader indexes also gained, with the Standard & Poor's 500 surpassing its all-time high, set last October.

Volume, however, remained light at the close, with 137.8 million shares traded, up from Friday's sluggish 121.01 million.

IBM, which was featured in the latest issue of Barron's magazine as regaining its star status, stole the limelight with gains of 3 5/8 at 119 7/8, breaking through a key 117-118 range set late last summer. Friday, IBM tumbled 2 1/2 in an overall slide in high-tech issues that brought the Dow down 34 points.

Some dealers said there were institutional players in the market with large amounts of cash to put to work in sectors such as high-tech and blue-chip stocks where there were bargains, but others dismissed this.

"I'm very skeptical of that," said Thomas Brown, strategist at Rutherford, Brown and Catherwood of Philadelphia. "There's a lot of cash to be put to work, but this kind of buying is {focused on} a pretty narrow list {of stocks}. Volume is minuscule. If it were a broad day's move with lots of institutional players, you'd see volume up over 200 million. But {137 millions shares} is hardly anything."

Some analysts were thanking Soviet President Mikhail Gorbachev for the post-holiday rally, noting that summits often boost stock prices, particularly since Gorbachev's rise to power. Also helping to sustain the bullish sentiment were half-point gains in the long bond and a rebound in the dollar against a weakened yen.

At the close, the Dow was up 49.57 at 2870.49, with advances leading declines by better than 2 to 1.

Blue-chip issues all closed higher, except for Merck & Co., which dipped 1/4 to 83 1/4. Aside from IBM's gains, Procter & Gamble spiked 2 1/4 to 80, Allied Signal Inc. leapt 1 7/8 to 36 1/2 and Coca-Cola jumped 1 5/8 to 45 1/2.

High-technology was the day's prime sector gainer, but other areas such as energy, consumer and bank stocks also were winners.

Among today's high-tech stars were Digital Equipment, up 2 1/4 at 94 3/4, Compaq Computer up 1 3/4 at 120 3/8 and Honeywell up 1 1/2 at 99 3/4. Adobe Systems, which had set off Friday's slump in high-tech stocks by losing more than 30 percent, recovered 2 5/8 to 37 7/8 on the over-the-counter market.

Time Warner gained 3 3/8 to 109 after a report in Barron's suggested the stock might be undervalued after two weeks of pounding from traders fearful that profits from cable television units would suffer from an anticipated return to government price controls.

Chevron rose 1 5/8 to 69 3/8, Atlantic Richfield gained 1 1/2 to 118 1/4, Mobil jumped 1 1/8 to 61 7/8 and Exxon rose 1 1/8 to 47 5/8. Royal Dutch Petroleum, the second most-active on the New York Stock Exchange with 2.3 million shares traded, gained 1 1/4 to 76 5/8.

Bank stocks continued a strong showing that began earlier this month. Bank analysts said they are assuming that banks put out their worst news in the first quarter, and that bank earnings in general will improve in the second quarter.

Wells Fargo and Co. closed up 1 7/8 at 78 1/8. Today, the American Banker, a banking trade publication, reported that large California banks are said to be considering a bid for Gibraltar Savings Bank, a thrift under federal conservatorship.

Other winners in that sector were Security Pacific Corp., up 1 1/8 at 39 7/8, Chemical Banking Corp., up 1/4 at 27 3/8 and J.P. Morgan, up 5/8 at 38.

The Dow transportation index rose 9.77 to close at 1162.52. Federal Express led the gainers, up 1 3/8 at 47 1/8.

The broad indexes all posted gains. The NYSE Composite closed up 2.86 at 196.57, the Value Line rose 2.12 to 285.92, the Standard & Poor's 500 climbed 6.07 to 360.65 and the Nasdaq was up 3.82 at 457.51.