Hans Reiser is a computer programmer, system engineer and the founder of Namesys, a software company based in California. He is best known for the development and creation of the ReiserFS and Reiser4 file systems, which are advanced journaling file systems that are used in several versions of Linux.

However, he is also known for a notorious criminal case in which he was the defendant. In October 2006, Reiser's wife, Nina Reiser, a Russian national who had been living in the United States, disappeared. Subsequent investigations led the police to suspect that Hans Reiser was involved in his wife's disappearance. In 2008, he was found guilty of first-degree murder after a six-month trial, despite the fact that Nina's body had not been found at that point.

In an attempt to reduce his sentence, Reiser later led police to the hidden remains of his wife in the Oakland hills. He revealed that he had strangled Nina Reiser during an argument while their children played one floor below. Thanks to his cooperation, his sentence was reduced from 25 years to life to 15 years to life.

Though the criminal case has certainly overshadowed his technical contributions, Reiser's work on the file system has left an impact on the Linux system. However, his prison sentence has led to the ceasing of progress and development on the Reiser file system, eventually leading to its deprecation in many distributions of Linux since other alternatives were more actively maintained.

To sum up, while Hans Reiser did contribute to the technology realm, his personal life, specifically his criminal case, has largely overshadowed that legacy.

The title of the youngest and oldest elected President of the United States goes to two distinct individuals.

The youngest elected president was President John F. Kennedy. He was 43 years old when he was inaugurated on January 20th, 1961. Kennedy was also the first Roman Catholic president and the youngest person elected to the presidency. He served from 1961 until his assassination in 1963. As President, he confronted mounting Cold War tensions in Cuba, Vietnam and elsewhere, and his tenure also saw advances in civil rights, the establishment of the Peace Corps, and the first manned American space flights.

The oldest elected president is President Joe Biden. Biden was 78 years old when he was inaugurated on January 20th, 2021. This marked Biden’s third run for the presidency and his election, coming in the midst of the Covid-19 pandemic, has set a new precedent in U.S. politics. Prior to his presidency, Biden served as Vice President under Barack Obama from 2009 to 2017. Joe Biden spent most of his career in politics and served in the U.S. Senate for Delaware before becoming Vice President.

These distinctions offer a fascinating look at the diverse range of leaders who have shaped American policies, both domestic and international, over the decades. Remember though, age is but a number and what truly matters is the caliber and character of leadership a President brings to the nation.

Sure, until now only three U.S. Presidents have been formally impeached by Congress: Andrew Johnson, Bill Clinton, and Donald Trump.

1. Andrew Johnson: The impeachment of Andrew Johnson occurred in 1868, in the turbulent aftermath of the American Civil War. It arose from clear political conflicts between Johnson, who had assumed the presidency after Lincoln’s assassination, and the Republican-dominated Congress. The main charge against Johnson arose when he dismissed War Secretary Edwin M. Stanton against the wishes of Congress. Congress had previously passed the Tenure of Office Act expressly to protect Stanton, stating that a president could not dismiss certain officeholders without the Senate's approval. Ignoring this, Johnson removed Stanton, leading to his impeachment. However, the Senate, by a single vote, did not convict him.

2. Bill Clinton: Clinton was impeached by the House of Representatives in 1998. The first charges, perjury and obstruction of justice, resulted from a sexual harassment lawsuit filed by Paula Jones. Clinton was accused of lying about the nature of his affair with Monica Lewinsky, a White House intern, and subsequently obstructing justice by encouraging others to lie. The second charge, perjury before a grand jury, related to the same matter. However, when the case went to the Senate in 1999, neither charge resulted in a conviction, due to the votes falling short of the necessary two-thirds majority.

3. Donald Trump: He holds the distinction of being the only U.S. president to be impeached twice by the House of Representatives.
- His first impeachment occurred in 2019. It focused on allegations that he sought help from foreign governments to discredit Joe Biden, his potential rival in the upcoming 2020 presidential election. The charges were abuse of power and obstruction of Congress. However, the Senate acquitted him of these charges in early 2020.
- Trump's second impeachment occurred in 2021, following the violent attack on the U.S. Capitol by some of his supporters. As a result, he was charged with “incitement of insurrection” for his role in inciting the attack. His trial began on February 9, 2021, after he had left office. He was acquitted by the Senate on February 13, 2021.

It's important to remember that impeachment by the House is essentially an accusation. The Senate then conducts a trial to determine whether to remove the president from office. To date, although three presidents have been impeached by the House, none have been removed from office by the Senate, as all were acquitted.

George Washington's presidency is often associated most commonly with his status as the first president of the United States, as well as his significant contributions during the American Revolutionary War. However, his presidency was also marked by many other lesser-known but equally important achievements. Here are a few:

1. **Establishment of the Cabinet System**: While the U.S. Constitution mentioned about heads of executive departments, it was Washington who established the cabinet system as we know it today. He appointed the Secretary of State, the Secretary of War (now Defense), the Secretary of the Treasury, and the Attorney General, establishing the President’s Cabinet as a crucial aspect of the Executive Branch.

2. **Enforcement of the "Supremacy of the Federal Law"**: Washington faced an early test of federal authority with the Whiskey Rebellion in 1794. When western Pennsylvania farmers resisted an excise tax imposed on whiskey, Washington personally led troops to enforce the law, thus establishing the supremacy of federal law over state or regional opposition.

3. **Southern Tour**: In 1791, Washington undertook a tour of the southern states to promote national unity at a time when travel for a president was challenging. His efforts created a sense of inclusiveness among the states.

4. **Avoidance of War with the Proclamation of Neutrality**: In 1793, when war broke out between France and Britain (both of whom were America's trade partners), he issued a Proclamation of Neutrality, steering America clear of a potentially ruinous war, thereby ensuring its economic and political stability.

5. **Outline of Foreign Policy**: His Farewell Address is still used as a canonical statement of American foreign policy. His advice has left a monumental legacy, guiding America's approach towards neutrality and caution in international matters.

6. **Creation of U.S. Financial System**: Washington worked with his Treasury Secretary, Alexander Hamilton, to build a financial system that allowed America to stand on her own two feet financially. This included a national bank, consolidated debt, and federal taxes.

These significant accomplishments, though less celebrated, greatly strengthened the new nation's domestic and global standing. Throughout his two terms, Washington worked tirelessly to create a smoothly functioning, effective federal government that could unify the disparate states and solidified the United States' position on the world stage.

President Abraham Lincoln enacted several major changes during the American Civil War that had a profound impact on the United States both during and after the war. Here are some of the key policies and changes:

1. Emancipation Proclamation (1862): Lincoln issued the Emancipation Proclamation in September 1862, after the Union victory at the Battle of Antietam. This declared that all slaves in Confederate-held territory were to be set free. This did not free all slaves immediately since it only applied in areas outside Union control, but its symbolic impact was immeasurable. It transformed the Union’s war aim from preserving the Union to ending slavery.

2. Suspension of Habeas Corpus (1861): Lincoln suspended the writ of habeas corpus during the Civil War, a measure he saw as necessary to maintain order and keep the border states in the Union. This allowed for the arrest and indefinite detention without trial of anyone suspected of being a Confederate sympathizer.

3. The Homestead Act of 1862: This law granted 160 acres of public land to settlers for a small fee, provided they improve the land by building a dwelling and cultivating crops. This encouraged Western expansion and is considered an early form of government social welfare.

4. Establishment of the Freedmen's Bureau (1865): In the year of his assassination, Lincoln organized the Bureau of Refugees, Freedmen, and Abandoned Lands—commonly called the Freedmen's Bureau—to assist freed slaves and poor whites in the South in the aftermath of the U.S. Civil War.

5. National Banking Acts of 1863 and 1864: These pieces of legislation created a system of nationally chartered banks, and provided for a system of new bank notes backed up by government bonds.

6. The Morill Act of 1862: This act granted each state 30,000 acres of federal land for every member of Congress representing the state. The lands were then to be sold and the funds used to establish colleges to teach agriculture and mechanical arts, leading to the foundation of many state-run universities.

These measures were incredibly transformative and impactful, not only helping to shape the outcome of the Civil War but also paving the way for a new era in United States history. Lincoln's policies directly led to the abolition of slavery, supported the preservation of the Union, bolstered economic growth, and promoted higher education and homesteading rights.

Yes, there has been one American President who has served non-consecutive terms in office: Grover Cleveland. He is the only President in American history who has managed this feat.

Grover Cleveland served as the 22nd President of the United States from 1885 to 1889, and later served his second, non-consecutive term as the 24th President from 1893 to 1897. His first run as president was on a Democratic ticket during a time of Republican domination in American politics. Cleveland had gained a reputation for integrity and honesty that helped him secure his first term. His second term was secured after the Republicans suffered from a series of scandals.

During his two terms, Cleveland was known for his fight against corruption, patronage, and general government inefficiency. His administration saw several significant events including the Pullman Strike, the Panic of 1893 (a serious economic depression in the United States that began in 1893), and the repeal of the Sherman Silver Purchase Act.

Future readers who are seeking to understand American Presidential history, navigating records or researching about non-consecutive terms in office, should note this specific episode as it marks a unique occurrence in the political landscape of the United States. Grover Cleveland's non-consecutive Presidency is more than a historical footnote, it underscores the dynamism and unpredictability of the American electoral system.

Franklin D. Roosevelt's 'New Deal' was a series of programs, public work projects, financial reforms, and regulations enacted by him in the United States between 1933 and 1939. The New Deal was Roosevelt's response to the Great Depression, which had caused severe economic hardship and unemployment across the country.

The New Deal is significant for several reasons:

1. **Economic Recovery**: The New Deal's programs aimed to stimulate economic recovery from the Great Depression. This included job creation programs like the Civilian Conservation Corps (CCC) and the Works Progress Administration (WPA), which provided employment to millions of people and launched large-scale public works projects.

2. **Regulation and Reform**: The New Deal saw the implementation of new regulations and reforms to prevent a future economic downturn as severe as the Great Depression. These included the establishment of the Federal Deposit Insurance Corporation (FDIC) to insure bank deposits and the Securities and Exchange Commission (SEC) to regulate the stock market and prevent fraud or abuse.

3. **Social Security**: The New Deal also marked the introduction of the Social Security Act in 1935, establishing benefits for the elderly, the unemployed, and children in low-income families. This was a significant shift in federal responsibility for social welfare in the U.S.

4. **Labor rights**: The New Deal also brought significant changes to labor rights, including the recognition of labor unions and the right to collective bargaining through the National Labor Relations Act, also known as the Wagner Act.

The New Deal remains significant because it fundamentally reshaped and expanded the role of federal government in American society and the economy. Many of its reforms, such as Social Security and labor protections, continue to form the backbone of America's social welfare and economic systems today. Furthermore, the New Deal is often brought up in policy discussions related to financial reform and social welfare policy.

Lastly, from a historical perspective, the New Deal serves as a case study in large-scale government intervention in times of economic crisis. It can be seen as a model, a warning, or a point of comparison, depending on one's political or economic perspectives, for similar interventions in the future.

Thomas Jefferson is recognized as one of the key figures in America's early history, responsible for a multitude of significant contributions. However, Jefferson did not directly participate in drafting the U.S. Constitution, as during that time period (1787) he was serving as the U.S. Minister to France.

Nevertheless, his ideas and earlier works influenced the framers who formulated the Constitution. Jefferson's ideas formed the bedrock of principles including natural rights, separation of powers, and checks and balances that would eventually be ingrained in the Constitution. These ideas were heavily reflected in the Declaration of Independence, which focused on individual rights and freedom, and greatly influenced the Constitution indirectly.

1. **Author of the Declaration of Independence:** While not the Constitution, Jefferson’s authorship of the Declaration of Independence laid the groundwork for American democracy. His it's included powerful concepts about human rights (“all men are created equal”), the consent of the governed, and the right to alter or abolish oppressive governments that heavily influenced the democratic values the Constitution defends.

2. **Advocate for a Bill of Rights:** Jefferson was a pivotal figure in convincing James Madison of the necessity for a Bill of Rights. Through their correspondence while Jefferson was in Paris, it's clear that his influence played a significant role in Madison’s shift towards supporting a Bill of Rights, which eventually became a crucial part of the Constitution.

3. **Influence on Madison:** Jefferson was close with James Madison, who is often hailed as the "Father of the Constitution." Madison was instrumental in the actual drafting and formulation of the Constitution, but it’s fair to state that Jefferson's ideas would have influenced Madison given their close professional and personal relationship.

4. **Founding Father Contributions:** More broadly, as a Founding Father, Jefferson shaped the ideological direction of the country which is reflected in the principles laid out in the Constitution.

5. **States' Rights Advocate:** Jefferson was a major advocate for states' rights, which are enshrined in the 10th Amendment of the Constitution. His vision inspired the concept of federalism, a system of government where power is divided between the national and state governments.

It's worth noting that when Jefferson did return to America, he had severe reservations about certain aspects of the Constitution, particularly the absence of a Bill of Rights. This led to his aforementioned advocacy, which ultimately led to the addition of The Bill of Rights in 1791.

So while Jefferson was unavailable to directly shape the Constitution, his influence in the core principles of natural rights, separation of powers, and checks & balances is undeniable, as are his efforts to add a Bill of Rights.

Richard Nixon's resignation as President of the United States on August 8, 1974, was the result of a complex series of events, scandals, and pressures, primarily stemming from the Watergate scandal and the subsequent investigations.

1. The Watergate Scandal: The Watergate scandal began with the arrest of five men for breaking into the Democratic National Committee headquarters at the Watergate complex in Washington D.C. on June 17, 1972. These men were connected to Nixon's reelection campaign, the Committee to Reelect the President (later known as CREEP).

2. Cover-Up: Following the break-in, the Nixon administration attempted to cover up its involvement, with measures that included destroying evidence and paying hush money to the burglars. When the burglars were tried in January 1973, the FBI linked the payments to a slush fund used by the Committee to Reelect The President.

3. Investigation and Revelation: In 1973, two reporters from The Washington Post, Bob Woodward and Carl Bernstein, began covering the story and slowly uncovered details linking the White House to the break-in and subsequent cover-up. At the same time, investigations by a specially appointed Special Prosecutor and the Senate Watergate Committee were ongoing.

4. The "Saturday Night Massacre": Nixon ordered Attorney General Elliot Richardson to fire the independent special prosecutor Archibald Cox, who was investigating the ensuing scandal. Richardson refused and resigned in protest, leading to a series of resignations and firings known as the "Saturday Night Massacre" in October 1973. This incident increased public outcry and led to calls for impeachment.

5. The Tapes: During the Senate Watergate hearings, it came to light that Nixon had a secret taping system that recorded conversations in the Oval Office. The tapes were subpoenaed, but Nixon refused to release them, citing executive privilege. Eventually, the Supreme Court ruled in United States v. Nixon that Nixon must release the tapes. One of these tapes, known as the "smoking gun" tape, revealed that Nixon had been involved in the cover-up from the beginning.

6. Impeachment Proceedings: In response to the mounting evidence, in July 1974, the House Judiciary Committee approved three articles of Impeachment: Obstruction of Justice, Abuse of Power, and Contempt of Congress.

Faced with almost certain impeachment by the House of Representatives and probable conviction by the Senate, Nixon decided to resign from the presidency. His vice president, Gerald Ford, was sworn in as President and later granted Nixon a full pardon for any crimes he may have committed while in office.

The American Presidents who were in office during the first and second World Wars are as follows:

World War I (July 28, 1914, to November 11, 1918):
- Thomas Woodrow Wilson served as the 28th President of the United States from March 4, 1913, to March 4, 1921. Wilson's second term in office coincided with the American entrance into World War I in 1917. Under his leadership, the US provided significant material resources and manpower to the Allied war effort.

World War II (September 1, 1939, to September 2, 1945):
- Franklin Delano Roosevelt was the 32nd President of the United States. He was in office from March 4, 1933, to April 12, 1945. When the U.S. entered World War II after the attack on Pearl Harbor in December 1941, Roosevelt played a significant role in mobilizing the economy for war and leading the Allies. He passed away in office, a few months before the end of World War II.
- Harry S. Truman assumed the presidency upon Roosevelt's death on April 12, 1945, and served until January 20, 1953. He led the country through the last few months of World War II and made the decision to use nuclear weapons against Japan, leading to the end of World War II.

These presidents lead the United States through periods of immense global conflict and their actions and policies during their tenure profoundly shaped the course of history.