First Ever.

Sir Roger Bannister

Sir Roger Bannister in 2009
Personal information
Born	23 March 1929 (age 82) Harrow, England
Height	6'2" (187 cm)
Weight	154 lbs (70 kg)
Sport
Sport	Running
Event(s)	800m,1500m,1 mile.
Medal record[hide] Competitor for  England and  Great Britain British Empire and Commonwealth Games Gold 1954 Vancouver 1 mile European Championships Bronze 1950 Brussels 800 m Gold 1954 Bern 1.500 metres

Sir Roger Gilbert Bannister, CBE (born 23 March 1929) is an English former athlete best known for running the first mile in less than 4 minutes. Bannister became a distinguished neurologist and Master of Pembroke College, Oxford, before retiring in 2001.

Sergey Bubka

Sergey Bubka in 2007
Personal information
Birth name	Сергій Назарович Бубка
Nationality	Ukrainian
Born	4 December 1963 (age 48) Voroshilovgrad, USSR (nowLuhansk, Ukraine)
Website	http://www.sergeybubka.com/
Sport
Sport	Pole vault
Medal record[hide] Men's athletics Competitor for the  Soviet Union Olympic Games Gold 1988 Seoul Pole vault World Championships Competitor for the  Soviet Union Gold 1983 Helsinki Pole vault Gold 1987 Rome Pole vault Gold 1991 Tokyo Pole vault Competitor for  Ukraine Gold 1993 Stuttgart Pole vault Gold 1995 Gothenburg Pole vault Gold 1997 Athens Pole vault World Indoor Championships Competitor for the  Soviet Union Gold 1985 Paris Pole vault Gold 1987 Indianapolis Pole vault Gold 1991 Sevilla Pole vault Competitor for  Ukraine Gold 1995 Barcelona Pole vault European Championships Competitor for the  Soviet Union Gold 1986 Stuttgart Pole vault

Serhiy Nazarovych Bubka (Ukrainian: Сергі́й Наза́рович Бу́бка; Russian: Серге́й Наза́рович Бу́бка, Sergey Nazarovich Bubka; born 4 December 1963) is a retired Ukrainian pole vaulter. Repeatedly voted the world's best athlete,^[1][2] he represented the Soviet Union until its collapse in 1991.

Bubka won 6 consecutive IAAF World Championships, an Olympics gold and broke the world record for men's pole vaulting 35 times^[3] (17 outdoor and 18 indoor records). He was the first to clear 6.0 metres and the only (as of March 2011) to clear 6.10 metres (20 ft).^[4][5]

Nadia Comăneci
Personal information
Full name	Nadia Elena Comăneci
Country represented	Romania
Born	November 12, 1961(age 50) Onești
Discipline	Women's artistic gymnastics
Gym	National Training Center
Former coach(es)	Béla Károlyi; Marta Károlyi
Choreographer	Geza Pozar
Eponymous skills	Comăneci salto (uneven bars)
Retired	1981
Medal record[hide] Olympic Games Gold 1976 Montréal All-Around Gold 1976 Montréal Uneven Bars Gold 1976 Montréal Balance Beam Gold 1980 Moscow Balance Beam Gold 1980 Moscow Floor Silver 1976 Montréal Team Silver 1980 Moscow Team Silver 1980 Moscow All-Around Bronze 1976 Montréal Floor World Championships Gold 1978 Strasbourg Balance Beam Gold 1979 Ft. Worth Team Silver 1978 Strasbourg Team Silver 1978 Strasbourg Vault European Championships Gold 1975 Skien All-Around Gold 1975 Skien Uneven Bars Gold 1975 Skien Balance Beam Gold 1975 Skien Vault Gold 1977 Prague All-Around Gold 1977 Prague Uneven Bars Gold 1979 Copenhagen All-Around Gold 1979 Copenhagen Vault Gold 1979 Copenhagen Floor Silver 1975 Skien Floor Silver 1977 Prague Vault Bronze 1979 Copenhagen Balance Beam Summer Universiade Gold 1981 Bucharest Team Gold 1981 Bucharest All-Around Gold 1981 Bucharest Uneven Bars Gold 1981 Bucharest Vault Gold 1981 Bucharest Floor

Nadia Elena Comăneci (Romanian pronunciation: [ˈnadi.a koməˈnet͡ʃʲ]; born November 12, 1961) is a Romanian gymnast, winner of three Olympic gold medals at the 1976 Summer Olympics in Montreal, Quebec, Canada, and the first female gymnast ever to be awarded a perfect score of 10 in an Olympic gymnastic event. She is also the winner of two gold medals at the 1980 Summer Olympics. She is one of the best-known gymnasts in the world.^[1][2][3] In 2000 Comăneci was named as one of the athletes of the century by the Laureus World Sports 

Academy.^[4]

Javier Sotomayor

Sotomayor in 2009
Personal information
Nationality	Cuban
Born	13 October 1967 (age 44) Limonar, Matanzas, Cuba
Height	1.95 m (6 ft 5 in)
Weight	82 kg (180 lb)
Sport
Sport	Track and field
Event(s)	High jump
Medal record[hide] Competitor for  Cuba Men's athletics Olympic Games Silver 2000 Sydney High jump Gold 1992 Barcelona High jump World Championships Gold 1997 Athens High jump Silver 1995 Gothenburg High jump Gold 1993 Stuttgart High jump Silver 1991 Tokyo High jump Pan American Games Gold 1995 Mar del Plata High jump Gold 1991 Havana High jump Gold 1987 Indianapolis High jump World Indoor Championships Gold 1999 Maebashi High jump Gold 1995 Barcelona High jump Gold 1993 Toronto High jump Gold 1989 Budapest High jump Silver 1985 Paris High jump CAC Championships Gold 1989 San Juan High jump Gold 1985 Nassau High jump Bronze 1983 Havana High jump Universiade Gold 1989 Duisburg High jump Pan American Junior Championships Gold 1986 Winter Park High jump

Javier Sotomayor Sanabria (born 1967) is a Cuban former track and field athlete who specialized in the high jump and is the current world record holder.^[1] The 1992 Olympic champion, he was the dominant high jumper of the 1990s; he is the only person ever to have cleared 8 feet (2.44 meters). He is widely regarded as the best high jumper of all time. Cuban boycotts of the Olympics in 1984 and 1988 and an injury in 1996 cost him chances at additional Olympic medals, but he returned to win the silver medal at the 2000 Olympics in Sydney. Sotomayor retired in 2001, pre-empting a lifetime ban for his second positive doping test (first for cocaine, then for anabolic steroids).

Edward Jenner..did the first vaccination 

Louis Pasteur
Louis Pasteur photographed by Pierre Lamy Petit
Born	December 27, 1822 Dole, Jura, Franche-Comté, France
Died	September 28, 1895 (aged 72) Marnes-la-Coquette, Hauts-de-Seine, France
Nationality	French
Fields	Chemistry Microbiology
Institutions	Dijon Lycée University of Strasbourg Université Lille Nord de France École Normale Supérieure
Alma mater	École Normale Supérieure
Notable students	Charles Friedel[1]
Signature

First ever.

Sir Roger Gilbert Bannister, CBE (born 23 March 1929) is an English former athlete best known for running the first mile in less than 4 minutes. Bannister became a distinguished neurologist and Master of Pembroke College, Oxford, before retiring in 2001.

Nadia Elena Comăneci (Romanian pronunciation: [ˈnadi.a koməˈnet͡ʃʲ]; born November 12, 1961) is a Romanian gymnast, winner of three Olympic gold medals at the 1976 Summer Olympics in Montreal, Quebec, Canada, and the first female gymnast ever to be awarded a perfect score of 10 in an Olympic gymnastic event. She is also the winner of two gold medals at the 1980 Summer Olympics. She is one of the best-known gymnasts in the world.^[1][2][3] In 2000 Comăneci was named as one of the athletes of the century by the Laureus World Sports Academy.^[4]

Serhiy Nazarovych Bubka (Ukrainian: Сергі́й Наза́рович Бу́бка; Russian: Серге́й Наза́рович Бу́бка, Sergey Nazarovich Bubka; born 4 December 1963) is a retired Ukrainian pole vaulter. Repeatedly voted the world's best athlete,^[1][2] he represented the Soviet Union until its collapse in 1991.

Bubka won 6 consecutive IAAF World Championships, an Olympics gold and broke the world record for men's pole vaulting 35 times^[3] (17 outdoor and 18 indoor records). He was the first to clear 6.0 metres and the only (as of March 2011) to clear 6.10 metres (20 ft).^[4][5]

Stem Cells

Cells are the building blocks of life. Your body is made up of millions and millions of cells. Different parts of your body are made of different cells. You have skin cells, blood cells, bone cells, brain cells, and cells for every other part.

Stem cells are one kind of cell found in your body. Stem cells are “blank” cells. They turn into the different cells in your body. Stem cells can turn into the skin, blood, bone, and brain cells.

Some scientists were studying stem cells, and now these scientists think that stem cells can cure diseases. Scientists found ways to make the stem cells grow hair, for bald people, and organs like livers and kidneys, for people whose organs don't work anymore. These scientists are finding more and more things to do with stem cells.

It costs a lot of money to study stem cells. The scientists that are trying to turn stem cells into cures are having a really hard time paying their bills. In the past, rich people who liked science would give money to these scientists. This is called “private funding”. To “fund” someone is to give money to them. It's “private” because it isn't money from the government. In America , the President, Mr. Bush, decided that it's not fair to give money to some of these scientists. This means that he doesn't believe in “public funding”, or giving the people money from the government. Mr. Bush doesn't want them to study some stem cells because of where those stem cells come from.

Some other countries' leaders agree with Mr. Bush here in America . They don't think that stem cells are as cool as some scientists say they are. But there are other countries whose leaders really like stem cell research, and hope that the stem cells will someday be able to cure a lot of sick people. Some scientists from America that can't pay for their research are moving to other countries. The governments of those countries will pay for the research of these scientists.

What do you think? Do you think scientists should be allowed to study stem cells? Who should pay for the research?

Medical researchers believe that stem cells have the potential to be used to cure various diseases as well as replace organs and vital tissues in the body. Adult stem cells, undifferentiated cells that create the differentiated cells of the body, are already being used to treat over a hundred diseases and conditions. Many of the ethical issues that critics take with stem cells collected from blastocysts, which must be destroyed after harvesting, are thus circumvented with collection from full-grown adults. But adult stem cells also have many limitations, including being only present in minute qualities, possibly.

Hitler Publishes Mein Kampf..1925 ( Wikipaedia)

Mein Kampf
Most common cover of Mein Kampf.
Author(s)	Adolf Hitler
Country	Germany
Language	German
Genre(s)	Autobiography, Political theory
Publisher	Eher Verlag
Publication date	July 18, 1925
Pages	720
Followed by	Zweites Buch

In Mein Kampf, Hitler uses the main thesis of "the Jewish peril", which speaks of an alleged Jewish conspiracy to gain world leadership.^[6] The narrative describes the process by which he became increasingly anti-semitic and militaristic, especially during his years in Vienna. Yet, the deeper origins of his anti-semitism remain a mystery. He speaks of not having met a Jew until he arrived in Vienna, and that at first his attitude was liberal and tolerant. When he first encountered the anti-semitic press, he says, he dismissed it as unworthy of serious consideration. Later he accepted the same anti-semitic views, which became crucial in his program of national reconstruction.

Mein Kampf has also been studied as a work on political theory. For example, Hitler announces his hatred of what he believed to be the world's twin evils: Communism and Judaism. The new territory that Germany needed to obtain would properly nurture the "historic destiny" of the German people; this goal, which Hitler referred to as Lebensraum (living space), explains why Hitler aggressively expanded Germany eastward, specifically the invasions of Czechoslovakia and Poland, before he launched his attack against Russia. In Mein Kampf Hitler openly states that the future of Germany "has to lie in the acquisition of land in the East at the expense of Russia."^[7]

In his work, Hitler blamed Germany’s chief woes on the parliament of the Weimar Republic, the Jews, and Social Democrats, as well as Marxists. He announced that he wanted to completely destroy the parliamentary system, believing it in principle to be corrupt, as those who reach power are inherent opportunists.

Michael Collins Killed in Ambush..1916

Michael Collins played a major part in Ireland's history after 1916. Michael Collins had been involved in the Easter Uprising in 1916, but he played a relatively low key part. It was after the Uprising that Collins made his mark leading to the treaty of 1921 that gave Ireland dominion status within the British Empire.

Michael Collins was born in October 1890 in County Cork. This area was a heartland of the Fenian movement. His father, also called Michael, instilled in his son a love of Irish poetry and ballads. At school, Michael was taught by a teacher called Denis Lyons who belonged to the Irish Republican Brotherhood and the village blacksmith, James Santry, was a Fenian. He told the young Michael stories of Irish patriotism and in such an environment, Michael grew up with a strong sense of pride in Ireland and of being Irish.

When he was 15, Collins emigrated to London. He worked as a clerk for the Post Office and he lived within the large Irish community in London. This community was never absorbed into London's society itself. There were many people in London who felt that the Irish undercut the wages paid out to other workers and many in the Irish community felt ostracised. While in London, Collins joined Sinn Fein and the Gaelic League and in 1909, he became a member of the Irish Republican Brotherhood.

In 1916, Collins returned to Ireland to take part in the Uprising in Dublin. He fought alongside others in the General Post Office. He played a relatively minor part and was not one of the leaders who was court-martialed.

The inside of the General Post Office after the surrender

Collins was sent to Richmond Barracks and then to Frongoch internment camp in Wales. He was released in December 1916 and immediately went back to Ireland. His goal now was to revitalise the campaign to get independence for Ireland. Collins was elected to the executive committee of Sinn Fein and he led a violent campaign against anything that represented British authority in Ireland - primarily the Royal Irish Constabulary (RIC) and the Army. The murder of RIC officers brought a tit-for-tat policy from the British. Ireland, post-World War One, was a dangerous country to be in. The more killings that were carried out by Collins and the men he led in the newly formed Irish Republican Army (IRA), the more the British responded with like. 

The notorious Black and Tans and the 'Auxies' were used by the British Army to spread fear throughout Ireland (though primarily in the south and west). Violence led to more violence on both sides. On November 21st, 1920, the IRA killed 14 British officers in the Secret Service. In reprisal, the British Army sent armoured vehicles onto the pitch at Croke Park where people were watching a football match, and opened fire on them. Twelve people were killed. In May 1921, the IRA set fire to the Custom House in Dublin - one of the symbols of Britain's authority in Ireland. However, many of those in the Dublin IRA were captured as a result of this action. The British Prime Minister, David Lloyd George, was given some blunt advice by his military commanders in Ireland. "Go all out or get out" - meaning that the army should be allowed to do as it wished to resolve the problem, or if this was not acceptable at a political level, the British should pull out of Ireland as the army was in an un-winnable position as matters stood then.

Eamonn de Valera, considered to be the leading republican politician in Ireland, sent Collins to London in October 1921 to negotiate a treaty. It was generally recognised by both sides that the situation as it stood in Ireland could not be allowed to continue. The difficult negotiations took three months before the treaty was signed by Collins and Arthur Griffiths. In December 1921, it was agreed that Ireland should have dominion status within the British Empire; i.e. that Ireland could govern itself but remain within the British Empire. The six northern counties were allowed to contract out of the treaty and remain part of the United Kingdom. To Collins, the treaty was simply the start of a process that, in his eyes, would lead to full independence for what was now the Irish Free State.

Collins is said to have commented when he signed the treaty that:

"I tell you, I have signed my death warrant"

There were many in the south who believed that Collins had betrayed the republican movement. These people, including de Valera, wanted an independent and united Ireland. Some believed that Collins had sold out to the British government. Few seemed to realise that Collins was not a politician and that he had been put into a situation in which he had no experience of what to do. He was up against British politicians who were experienced in delicate negotiations. Some have argued that de Valera deliberately put Collins in this situation knowing that if he came back with an unacceptable treaty, it would seriously damage the reputation of Collins and weaken whatever political kudos he had in Ireland - therefore removing any potential threat he may have been to de Valera at a political level. It is known that Collins did not feel that he had the necessary knowledge and experience to get what was wanted and he asked de Valera to send others instead of him. Some, such asCountess Markievicz, openly called Collins a traitor to the cause.

The Dáil accepted the treaty by just seven votes. This, in itself, seemed a justification of what Collins had set out to achieve. Arthur Griffiths replaced De Valera as president of the Dáil and Collins was appointed chairman of the provisional government which would take over Ireland once the British had left. Those who did not support the treaty fell back on violence and a civil war took place in Ireland from April 1922 to May 1923. The IRA split into the 'Regulars' (those who supported the treaty) and the 'Irregulars' (those who did not).

On August 22nd, 1922, Collins journeyed to County Cork. He was due to meet troops of the new Irish Army. His car was ambushed at a place called Beal na mBlath and Collins was shot dead. To this day, no-one is completely sure what happened or who killed him. No-one else was killed in the ambush. Collins' body lay in state in Dublin for three days and thousands paid their respects. Thousands also lined the streets for his funeral procession.

Genetics.1

1):Introduction to How DNA Evidence Works
At a microscopic level, we are all composed of cells. Look at yourself in a mirror -- what you see is about 10 trillion cells divided into about 200 differen­t types. Our muscles are made of muscle cells, our livers of liver cells, and there are even very specialized types of cells that make the enamel for our teeth or the clear lenses in our eyes!

It's hard to believe that DNA evidence has come so far so fast. The techniques that make it possible to identify a suspect using his or her unique genetic blueprint have only been around since 1985. That's when Alec Jeffreys and his colleagues in England first demonstrated the use of DNA in a criminal investigation. Since then, DNA evidence has played a bigger and bigger role in many nations' criminal justice systems. It has been used to prove that suspects were involved in crimes and to free people who were wrongly convicted. And, in the United States, it has been integral to several high-profile criminal cases.

At the heart of DNA evidence is the biological molecule itself, which serves as an instruction manual and blueprint for everything in your body (see How Cells Work for details). A DNA molecule is a long, twisting chain known as a double helix. DNA looks pretty complex, but it's really made of only four nucleotides:

• Adenine
• Cytosine
• Guanine
• Thymine

These nucleotides exist as base pairs that link together like the rungs in a ladder. Adenine and thymine always bond together as a pair, and cytosine and guanine bond together as a pair. While the majority of DNA doesn't differ from human to human, some 3 million base pairs of DNA (about 0.10 percent of your entire genome) vary from person to person.

In human cells, DNA is tightly wrapped into 23 pairs of chromosomes. One member of each chromosomal pair comes from your mother, and the other comes from your father. In other words, your DNA is a combination of your mother's and your father's DNA. Unless you have an identical twin, your DNA is unique to you.

This is what makes DNA evidence so valuable in investigations -- it's almost impossible for someone else to have DNA that is identical to yours. But catching a criminal using DNA evidence is not quite as easy as "CSI" makes it seem, as this article will demonstrate. Our first step in exploring DNA evidence is the crime scene -- and the biological evidence gathered there by detectives.

Collecting DNA Evidence

The following list shows some common sources of DNA evidence:

• A weapon, such as a baseball bat, fireplace poker or knife, which could contain sweat, skin, blood or other tissue
• A hat or mask, which could contain sweat, hair or dandruff
• A facial tissue or cotton swab, which could contain mucus, sweat, blood or earwax
• A toothpick, cigarette butt, bottle or postage stamp, all of which could contain saliva
• A used condom, which could contain semen or vaginal or rectal cells
• Bed linens, which could contain sweat, hair, blood or semen
• A fingernail or partial fingernail, which could contain scraped-off skin cells

When investigators find a piece of evidence, they place it in a paper bag or envelope, not in a plastic bag. This is important because plastic bags retain moisture, which can damage DNA. Direct sunlight and warmer conditions may also damage DNA, so officers try to keep biological materials at room temperature. They label the bags with information about what the material is, where it was found and where it will be transported. These are chain-of-custody procedures, which ensure the legal integrity of the samples as they move from collection to analysis.

DNA Analysis: Traditional Techniques

 Let's look at some of these techniques in greater detail.

Restriction fragment length polymorphism (RFLP) analysis was one of the first forensic methods used to analyze DNA. It analyzes the length of strands of DNA that include repeating base pairs. These repetitions are known as variable number tandem repeats (VNTRs) because they can repeat themselves anywhere from one to 30 times.

RFLP analysis requires investigators to dissolve DNA in an enzyme that breaks the strand at specific points. The number of repeats affects the length of each resulting strand of DNA. Investigators compare samples by comparing the lengths of the strands. RFLP analysis requires a fairly large sample of DNA that hasn't been contaminated with dirt.

Many laboratories are replacing RFLP analysis with short tandem repeat (STR) analysis. This method offers several advantages, but one of the biggest is that it can start with a much smaller sample of DNA. Scientists amplify this small sample through a process known as polymerase chain reaction, or PCR. PCR makes copies of the DNA much like DNA copies itself in a cell, producing almost any desired amount of the genetic material.

Once the DNA in question has been amplified, STR analysis examines how often base pairs repeat in specific loci, or locations, on a DNA strand. These can be dinucleotide, trinucleotide, tetranucleotide or pentanucleotide repeats -- that is, repetitions of two, three, four or five base pairs. Investigators often look for tetranucleotide or pentanucleotide repeats in samples that have been through PCR amplification because these are the most likely to be accurate.

The Federal Bureau of Investigation (FBI) has chosen 13 specific STR loci to serve as the standard for DNA analysis. The likelihood that any two individuals (except identical twins) will have the same 13-loci DNA profile can be as high as 1 in 1 billion or greater.

DNA Analysis: Specialized Techniques

Although most labs use either RFLP or STR techniques for their DNA analysis, there are situations that require a different approach. One such situation is when there are multiple male contributors of genetic material, which sometimes happens in sexual assault cases. The best way to resolve the complex mixture and sort out exactly which men were involved is Y-marker analysis. As its name suggests, this technique examines several genetic markers found on the Y chromosome. Because the Y chromosome is transmitted from a father to all his sons, DNA on the Y chromosome can be used to identify DNA from different males. Y-marker analysis can also be used to trace family relationships among males.

Another situation involves identifying old remains or biological evidence lacking nucleated cells, such as hair shafts, bones and teeth. RFLP and STR testing can't be used on these materials because they require DNA found in the nucleus of a cell. In these cases, investigators often use mitochondrial DNA (mtDNA)analysis, which uses DNA from a cell's mitochondria. Investigators have found mtDNA testing to be very useful in solving cold cases, which are murders, missing-person cases or suspicious deaths that are not being actively investigated. Cold cases often have biological evidence in the form of blood, semen and hair that has been stored for a long time or improperly stored. Submitting those degraded samples for mtDNA testing can sometimes break the case open and help detectives find the perpetrator.

A relatively new technique -- SNP analysis -- is also useful in certain cases where forensic labs are presented with highly degraded DNA samples. This technique requires that scientists analyze variations in DNA where one nucleotide replaces another. Such a genetic change is called a single nucleotide polymorphism, or SNP (pronounced "snip"). SNPs make excellent markers and are most often used to determine a person's susceptibility to a certain disease. But forensics labs turn to SNP analysis on occasion. For example, forensic scientists used SNP technology successfully to identify several Sept. 11 World Trade Center victims for whom other methods had failed.

In reality, analyzing a DNA sample is just a first step. Up next, we'll take a look at what happens after the analysis is complete.

When forensic scientists examine DNA in the lab, each sample appears as a unique sequence of dark bars. Patterns of bars are compared to find a match. In the hypothetical example shown here, it looks like suspect #2 left some DNA at the crime scene.

Computer and its various parts.

The word computer refers to an object that can accept some input and produce some output. In fact, the human brain itself is a sophisticated computer, and scientists are learning more about how it works with each passing year. Our most common use of the word computer, though, is to describe an electronic device containing a microprocessor.

A microprocessor is a small electronic device that can carry out complex calculations in the blink of an eye. You can find microprocessors in many devices you use each day, such as cars, refrigerators and televisions. The most recognized device with a microprocessor is the personal computer, or PC. In fact, the concept of a computer has become nearly synonymous with the term PC.

When you hear PC, you probably envision an enclosed device with an attached video screen, keyboard and some type of a pointing device, like a mouse or touchpad. You might also envision different forms of PCs, such as desktop computers, towers and laptops. The term PC has been associated with certain brands, such as Intel processors or Microsoft operating systems. In this article, though, we define a PC as a more general computing device with these characteristics:

• designed for use by one person at a time

• runs an operating system to interface between the user and the microprocessor

• has certain common internal components described in this article, like a CPU and RAM

• runs software applications designed for specific work or play activities

• allows for adding and removing hardware or software as needed

PCs trace their history back to the 1970s when a man named Ed Roberts began to sell computer kits based on a microprocessor chip designed by Intel. Roberts called his computer the Altair 8800 and sold the unassembled kits for $395. Popular Electronics ran a story about the kit in its January 1975 issue, and to the surprise of just about everyone, the kits became an instant hit. Thus, the era of the personal computer began [sources: Cerruzi, Lasar].

While the Altair 8800 was the first real personal computer, it was the release of the Apple II a couple of years later that signaled the start of the PC as a sought-after home appliance. The Apple II, from inventors Steve Jobs and Steve Wozniak, proved that there was a demand for computers in homes and schools. Soon after, long-established computer companies like IBM and Texas Instruments jumped into the PC market, and new brands like Commodore and Atari jumped into the game.

In this article, we'll look inside the PC to find out about its parts and what they do. We'll also check out the basic software used to boot and run a PC. Then, we'll cover mobile PCs and examine the future for PC technology.

Core PC Components

To see how a PC works, let's start with the pieces that come together to make up the machine. The following are the components common to PCs in the order they're typically assembled:

Case -- If you're using a laptop, the computer case includes keyboard and screen. For desktop PCs, the case is typically some type of box with lights, vents, and places for attaching cables. The size of the case can vary from small tabletop units to tall towers. A larger case doesn't always imply a more powerful computer; it's what's inside that counts. PC builders design or select a case based on the type of motherboard that should fit inside.

Motherboard -- The primary circuit board inside your PC is its motherboard. All components, inside and out, connect through the motherboard in some way. The other components listed on this page are removable and, thus, replaceable without replacing the motherboard. Several important components, though, are attached directly to the motherboard. These include the complementary metal-oxide semiconductor (CMOS), which stores some information, such as the system clock, when the computer is powered down. Motherboards come in different sizes and standards, the most common as of this writing being ATX and MicroATX. From there, motherboards vary by the type of removable components they're designed to handle internally and what ports are available for attaching external devices.

Power supply -- Other than its CMOS, which is powered by a replaceable CMOS battery on the motherboard, every component in your PC relies on its power supply. The power supply connects to some type of power source, whether that's a battery in the case of mobile computers, or a power outlet in the case of desktop PCs. In a desktop PC, you can see the power supply mounted inside the case with a power cable connection on the outside and a handful of attached cables inside. Some of these cables connect directly to the motherboard while others connect to other components like drives and fans.

Central processing unit (CPU) -- The CPU, often just called the processor, is the component that contains the microprocessor. That microprocessor is the heart of all the PC's operations, and the performance of both hardware and software rely on the processor's performance. Intel and AMD are the largest CPU manufacturers for PCs, though you'll find others on the market, too. The two common CPU architectures are 32-bit and 64-bit, and you'll find that certain software relies on this architecture distinction.

Random-access memory (RAM) -- Even the fastest processor needs a buffer to store information while it's being processed. The RAM is to the CPU as a countertop is to a cook: It serves as the place where the ingredients and tools you're working with wait until you need to pick up and use them. Both a fast CPU and an ample amount of RAM are necessary for a speedy PC. Each PC has a maximum amount of RAM it can handle, and slots on the motherboard indicate the type of RAM the PC requires.

Drives -- A drive is a device intended to store data when it's not in use. A hard drive or solid state drive stores a PC's operating system and software, which we'll look at more closely later. This category also includes optical drives such as those used for reading and writing CD, DVD and Blu-ray media. A drive connects to the motherboard based on the type of drive controller technology it uses, including the older IDE standard and the newer SATA standard.

Cooling devices -- The more your computer processes, the more heat it generates. The CPU and other components can handle a certain amount of heat. However, if a PC isn't cooled properly, it can overheat, causing costly damage to its components and circuitry. Fans are the most common device used to cool a PC. In addition, the CPU is covered by a metallic block called a heat sink, which draws heat away from the CPU. Some serious computer users, such as gamers, sometimes have more expensive heat management solutions, like a water-cooled system, designed to deal with more intense cooling demands.

Cables -- All the components we've mentioned so far are connected by some combination of cables. These cables are designed to carry data, power or both. PCs should be constructed so that the cables fold neatly within the case and do not block air flow throughout it.

A PC is typically much more than these core components. Next, we'll look at the ports and peripherals that let you interact with the computer and how you can add even more components using expansion slots.

BP Apparatus

Sphygmomanometers

What is blood pressure?

Blood pressure is the force exerted by the blood on blood vessel walls. Today, it's measured in millimeters of mercury, units that refer to the height to which a column of mercury is raised by an equivalent pressure.

Recording blood pressure leads to the discovery of hypertension

Although physiologists who studied animals knew about the phenomenon of blood pressure in the 1700s, it was many years before physicians figured out how to measure it in humans. As soon as doctors had an accurate device and a simple procedure for measuring blood pressure, it became a normal part of a medical exam. Physicians could detect and monitor blood pressure over time, and they soon discovered hypertension, or chronic high blood pressure, a widespread and life-threatening condition.

Unfortunately, doctors had few options for treating hypertension and little understanding of its causes. Sometimes kidney disease was associated with hypertension, but in most cases, no cause could be identified.

This 1863 sphygmograph was an early attempt to measure blood pressure that proved to be cumbersome and inaccurate. A spring pressed one end of a lever onto the wrist, compressing an artery. The lever rose and fell with each pulse wave. A recording device traced the movements on smoked paper.

This 1898 sphygmomanometer had a cuff that was too narrow. Later models with wider cuffs gave more accurate readings.

This 1901 model had a wide cuff, but doctors used their fingers to detect arterial blood flow as they watched for changes in pressure.

	In 1905, Russian surgeon Nikolai Korotkoff developed the modern technique of using a stethoscope to listen for the sounds of blood flowing through the artery. His method proved to be extremely accurate and led to the discovery of hypertension.

1920 mercury sphygmomanometer, the "Pilling Midget"

How to take a blood pressure reading, based on Korotkoff sounds

A modern sphygmomanometer

1. Place cuff snugly around the middle of the upper arm.
2. Place the bell of your stethoscope over the pulse point just below the cuff.
3. Pump up the cuff until it's tight enough to stop blood flow.
4. Slowly deflate the cuff and listen.
5. Note the pressure reading when you hear the first faint sounds—that means some blood has started to pass through the vessels under the cuff. This is the maximum, or systolic, pressure.
6. When all sounds stop, note the pressure reading again. Now blood is flowing freely. This is the minimum, or diastolic, pressure.
7. Record the blood pressure as systolic over diastolic.