`Ollie' North moves onto center stage. His name has been a leitmotif in the Iran-contra investigation. Today the central figure who has maintained a stony silence about the affair finally starts to talk.

LT. COL. OLIVER L. NORTH Childhood: Born Oct. 7, 1943, in San Antonio, to Ann and Army Col. Oliver Clay North. Grew up in Philmont, N.Y., in the Hudson River Valley.

Education: State University of New York at Brockport, 1961, English major. United States Naval Academy, entered 1963 but delayed by serious auto accident and graduated in class of 1968. International relations major, captain of plebe sailing team, stand-out boxer, company commander for two of three terms final year.

Early military career: Entered Marines in 1968. Official records show one tour of duty in Vietnam, 1968-69; ended as platoon commander. Instructor at Marine Basic School, Quantico, Va., 1969-73. Okinawa, head of Marine jungle training school, 1973-74. Marine Corps headquarters in Washington, manpower division, 1975-78. Battalion staff, Camp Lejeune, N.C., 1978-80.

White House experience: Detailed to National Security Council in August 1981 at direction of Navy Secretary John Lehman. Deputy director of politico-military affairs division. According to official biography, was responsible for crisis management and counter-terrorism, with a regional focus on political and military matters in Central and South America. Dismissed by President Reagan in 1986, when news of Iran-contra affair broke.

Current job: Attached to Marine headquarters in Washington.

Accomplishments: Military decorations include Silver Star, Bronze Star, two Purple Hearts. At NSC, credited with helping plan invasion of Grenada and capture of Achille Lauro hijackers, among other things. Promoted to present rank in March 1983.

Family: Married to the former Betsy Stuart. Four children: Tait, Stuart, Sarah, and Dornin.

-Peter Grier, Staff writer (The following by Gary Thatcher)

FOR the past eight months, a silent figure in olive drab has been at the center of Washington's political consciousness. Lt. Col. Oliver North, formerly a National Security Council (NSC) aide, this week publicly explains his role in the Iran-contra affair for the first time.

Two congressional committees, in joint hearings, have been conducting a public inquiry into the Byzantine process by which American arms were sold to Iran and some of the profits diverted to help the contra rebels fighting to overthrow the government of Nicaragua.

In six weeks of public testimony, many questions about Colonel North's role in the affair have been raised. Now he gets to tell his side of the story under a grant of limited immunity from prosecution.

What follows are some questions the investigators will almost certainly ask North, drawn from hundreds of hours and thousands of pages of testimony and documents. The answers could evoke some further surprising twists in the continuing drama of the Iran-contra affair.

Did President Reagan know that profits from the Iranian arms sales were being diverted to the Nicaraguan contras?

There has been no evidence directly implicating the President. Yet Mr. Reagan has claimed memory lapses about what he knew and when he knew it.

Normally, it would have been North's superior at the NSC, former national-security adviser John M. Poindexter, who would have briefed the President on such matters as the diversion of funds.

Did Poindexter do that? Did he tell North about it? If so, that would indicate that the President knew about efforts to circumvent United States law.

Did North profit personally from the Iranian arms sales or the contributions to the contras?

Congressional investigators have discovered that North personally cashed some $2,440 in traveler's checks provided to him by contra leader Adolfo Calero. The money was to be spent on behalf of the Nicaraguan resistance. But checks for $340 were cashed at Washington-area supermarkets. Another $220 worth were cashed at other merchants, including an automotive wholesaler that installed snow tires on North's car.

A former Central Intelligence Agency security specialist, Glenn Robinette, testified that he installed a $16,000 security system in North's home, and that it was paid for by retired Air Force Maj. Gen. Richard Secord. General Secord arranged for the secret arms shipments to Iran and the contras, and his private businesses stood to gain millions from future Iranian arms sales.

Yet, Robinette said, North asked for invoices, then prepared phony correspondence that made it appear he had intended to pay for the security devices himself.

It is against the law for a federal employee to accept a ``gratuity'' in return for performing his official duties.

Albert Hakim, an Iranian-American businessman who was a partner of General Secord, testified that he established a $200,000 account - under the pseudonym ``Button'' - for Colonel North. Mr. Hakim characterized the account as a ``death benefit'' to pay for the North children's educational expenses in the event he was killed.

Hakim also testified that North's wife, Betsy, took part in discussions to funnel thousands of dollars to her family.

Was there a cover-up of the Iran-contra affair?

A Justice Department official, Charles Cooper, has testified that North, Attorney General Edwin Meese III, former CIA Director William Casey, and Admiral Poindexter, then the national-security adviser, met in November 1986 to discuss Mr. Casey's upcoming congressional testimony about the Iran-contra affair. None of the participants objected, Cooper testified, when North suggested that Casey should claim that no US official knew of a November 1985 arms shipment from Israel to Iran. In fact, North had helped arrange the shipment and had received assistance from the CIA - facts that Poindexter and Casey almost certainly knew. It was only because of State Department objections that Casey dropped the misleading claim from his testimony, although he gave a less-than-complete account when he did testify.

Robert McFarlane, Poindexter's predecessor as national-security adviser, admitted that he helped concoct misleading chronologies of the arms sales in order to ``gild the President's motives'' in attempting to swap arms for hostages.

Did North willfully violate the Boland amendment, the congressional ban on aid to the contras?

Congress passed five different pieces of legislation, known collectively as the Boland amendment, that prevented US intelligence agencies from aiding the contras, directly or indirectly.

North apparently operated, at times, under the assumption that the Boland amendment did not apply to the NSC. He sought, and obtained, legal backing for that assumption.

Yet the source of the legal advice was questionable - a novice lawyer at an obscure federal advisory panel. Mr. McFarlane testified that, in his opinion, the Boland amendment clearly did apply to the NSC.

What was CIA head Casey's role?

Testimony to the congressional investigating committees has indicated that Casey was a guiding force behind the affair, using Colonel North as a willing water-carrier.

There is speculation that Casey enlisted North's collaboration to take advantage of the ambiguity surrounding the application of the Boland amendment to the NSC. The amendment unmistakably applied to the CIA.

Some observers portray the late Casey as North's mentor, a gray eminence who took secret delight at the exploits of a gung-ho Marine.

Why did North shred and alter NSC documents as the Iran-contra affair unraveled?

Fawn Hall, North's secretary, testified that she helped North shred an 18-inch stack of documents the night before Justice Department officials converged on his office to conduct an inquiry.

She also detailed how North instructed her to alter key documents and destroy the originals, in order to leave a misleading paper trail for investigators.

Was a ``smoking gun'' memo shredded - one that would have indicated that Reagan knew of the diversion of funds?

William Bradford Reynolds, an assistant attorney general, discovered a document in Colonel North's files outlining plans to divert money from the Iranian arms sales to the contras. North apparently wrote the document, but there was no indication to whom it was written.

Attorney General Meese confronted North with the paper, and North, according to testimony, seemed shocked. Later, he inquired whether anyone had found a cover memorandum.

``No,'' replied Reynolds.

``Should we have found a cover memo?'' asked Meese.

``No, I was just wondering,'' replied North.

Sen. William Cohen (R) of Maine, a member of the Senate investigating committee, suggests that a ``smoking gun'' will never be found - that it disappeared into a ``smoking shredder.''

If North's primary motivation in the contra resupply effort was to help the insurgents, why did he countenance an arrangement that gave private entrepreneurs the lion's share of money meant for the Nicaraguan rebels?

General Secord testified that only about $3.5 million of the $18 million profit from the Iranian arms sales actually went to the contras.

Secord's business partner, Albert Hakim, has claimed twice that amount as his share of profits from the deals. Secord even used some of the funds from the arms sales held in a secret Swiss bank account to buy himself a Porsche automobile, later claiming the money was a loan from Hakim.

Why were private citizens brought into the contra fund-raising effort and some of the other secret projects being conducted out of the NSC offices?

Private benefactors were solicited for contributions to the contras. Some were even shepherded into meetings with President Reagan. Others were shown lists of weapons that the contras could purchase with their contributions.

Yet private fund-raisers were raking off some of the contributions for themselves. Two of the fund-raisers who have pleaded guilty to a conspiracy to deprive the US government of tax revenues have named Colonel North as a third member of the conspiracy.

Does North feel betrayed by the Reagan administration?

Secord made a bitter attack on Attorney General Meese, charging that Mr. Meese ``prematurely'' went public with ``grossly inaccurate disclosures'' about the Iran-contra affair.

President Reagan initially called North a ``national hero,'' yet the White House released confidential medical reports that indicated North had been hospitalized in 1974 for 10 days to be treated for ``emotional distress.'' Secord called that disclosure unforgivable.

Is North protecting the President?

Thomas C. Green, North's attorney for a time, once told Meese that North was ``your ultimate marine, and he wants to step forward and take the spears in his own chest.''

Ironically, if North is protecting President Reagan, his actions have created a cloud over the Reagan presidency that may persist throughout the President's final 18 months in office.

North's former secretary, Fawn Hall, testified that sometimes it is necessary to `go above the written law' in the pursuit of a noble end. Does North agree?

(The following by Peter Grier)

Fawn Hall testified that anyone who wanted to understand Oliver North should read ``The Man in the Arena,'' by Theodore Roosevelt. She was referring to a phrase lifted from a famous speech given by the former President in 1910 at the Sorbonne in France.

``It's not the critic who counts, nor the man who points out how the strong man stumbled or where the doer of deeds could have done them better,'' Mr. Roosevelt said to an audience of French intellectuals. ``The credit belongs to the man in the arena.''

This man, ``whose face is marred by dust and sweat and blood, ... knows in the end the triumphs of high achievements and ... at the worst, if he fails, at least fails while daring greatly.''

The speech was also a favorite of ex-President Richard Nixon.