Also, a working-alphabet (set of characters) has to be defined.
When a Turing machine is started, a word (out of the working-alphabet) must be present on the infinite tape of the machine. The read/write-device on the first character now reads the first character and depending on the current state of Turing machine the read/write-device overwrites the character with a new one or moves one cell to the left or to the right. Furthermore, the current state of the machine can be switched.
For decidability theory a Turing machine is said to "decide a language" if it is always able to determine whether a given word is contained in a certain language or not. Therefore, the machine usually has two special states marked as "Accept" and "Reject". After a while one of the two states will be reached (depending on the input word) and the machine is halted. If only one of the two states will ever be reached, the Turing machine is said to "semi-decide" a language.
If a Turing machine is used for the computation of functions it only has one "end state". When the machine comes to that state it is halted and the result of the function (depending on the input) can be found on the tape.
Turing machines were not invented to be built in reality, but they are very important for theoretical computer science as they are one of the simplest models for computers. The Church-Turing thesis states that all computers are only as powerful as Turing machines. This can be used to prove if a problem is solvable by a computer or not.
Canadian football
Canadian football is football generally played in Canada and follows much the same general rules as American Football. Compared to American football, the field is slightly longer and wider, 110 by 65 yards (101 by 59 m) rather than 100 by 53 1/3 yards (91 by 49 m), and the endzones are 10 to 15 yards deeper. There are also only 3 downs instead of 4, and the field goal posts are at the front of the endzone instead of the back. There are 12 players per team on the field during play. More than one player may be in motion before the snap of the ball and the rules are less strict about players position relative to the line of scrimmage.
John Rhys-Davies
John Rhys-Davies (born 5 May 1944, in Ammanford, Carmarthenshire, Wales) is a British actor. Although he has played in many movies, Rhys-Davies is probably best known for his characters in two blockbuster movie series: Sallah in the "Indiana Jones" movies and the dwarf Gimli in the "Lord of the Rings" movie trilogy.
Sean Bean
Sean Bean (born as Shaun Mark Bean on 17 April 1959) is an English actor. As an actor, he adopted the Irish/Scottish spelling "Sean" of his first name. He was born in Handsworth, Sheffield, West Riding of Yorkshire.
Tripoli, Greece
Tripoli () is a city in Greece. It is in the center of the Peloponnese. It is built at an altitude of about 600 meters, at the bottom of Mainalo mountain. It had 28,876 people according to the 2001 census. Tripoli is the capital of Arcadia prefecture.
Tripoli is connected to the capital city Athens by a motorway between Corinth-Tripoli-Kalamata, which is a part of the E65.
2006 FIFA World Cup
The 2006 FIFA World Cup was a football (soccer) sporting event that was held in Germany from June 9 to July 9, 2006. 32 teams took part from many countries. Italy won the trophy after beating France in the final on penalties. Germany got third place at home.
Schedule
Polynesia
Polynesia is a group of over 1,000 islands in the Pacific Ocean.
Polynesia is the islands in a triangle in the Pacific Ocean. The top of the triangle is Hawai'i, the bottom left is New Zealand and the bottom right is Easter Island. All the islands inside the triangle are Polynesia.
Cocaine
Cocaine (also cocain) is a drug that is made from coca leaves. Cocaine is usually a white powder. Most cocaine is used as an illegal drug. Because it is a stimulant, cocaine gives people energy. It also makes people feel very happy when it is taken. When used this way, cocaine is very addictive. However, cocaine can also be used as a local anesthetic if it is applied topically (onto the skin or gums).
Cocaine is taken from the leaves of the coca plant. Coca plants are mostly grown in South America, in countries like Brazil or Argentina. When Spanish conquistadors (explorers) discovered coca plants, they sent them back to Europe. People started using cocaine as a medicine, as well as in drinks and food. This was because they did not know how damaging and addictive the drug could be when used.
In America, cocaine was used during surgery, or to treat toothaches. It was also put into drinks. When Coca-Cola was first made in 1885, it got the first part of its name from the "handful of coca leaves" added to the drink for energy. (The caffeine in the drink came from the kola nut, so the name "Coca-Cola" was chosen.) Cocaine was taken out of Coca-Cola completely by the 1920s because of pressure from groups in the United States.
When cocaine is applied topically (onto the skin or gums), it causes numbness.
When cocaine is chewed or eaten, inhaled into the nose ("snorted"), or injected into the veins, it causes people to feel euphoric (very happy), alert, very confident, and full of energy. This feeling is called being "high." Some people who take cocaine also have unpleasant feelings. They may feel worried, anxious, or even paranoid. They may also have physical symptoms, like shaking, a high heart rate, and high body temperature.
Cocaine cannot be smoked in its normal form. It must react with another chemical to form crack cocaine, which can be smoked. This is because burning normal cocaine destroys it, so the user does not get the effect they want.
As a stimulant, cocaine produces a state of euphoria, sexual arousal, increased energy, and mental alertness. Some people report that using cocaine helps them socialize and feel confident. However, as a person comes down from their high (crashes), they may feel the opposite effects—anxiety, irritability, insomnia, confusion, and paranoia.
People may use more and more of the drug in an attempt to keep their high and avoid the crash. This cycle can continue on and on. During binges, users may neglect eating or sleeping and become depressed, paranoid, or aggressive.
In most countries, it is illegal to make, sell, or use cocaine (unless it is being used for approved medical reasons).
As an illegal drug, cocaine can be used in its powder form, or it can be made into crack cocaine. Usually, crack is made by adding baking soda and water to cocaine and then heating the mixture. Crack is usually less expensive than the normal form of cocaine. Crack is usually smoked. It gives users a high that is very strong, but does not last as long as the high from regular cocaine. Both forms of cocaine are addictive, although crack cocaine is thought to be more addictive as it is usually smoked.
If people use cocaine, they may take too much and get sick or even die. This is called an "overdose". When people take cocaine, they get intoxicated as well. When a person is intoxicated, they may do dangerous things, such as having unsafe sex with a person they do not know, or getting into a violent fight with a person.
If a person uses cocaine for a long time, they can start to get strange feelings, like there are bugs crawling under their skin, or they can get paranoia (a feeling that there are people that want to hurt them).
Cocaine is a very addictive drug. It can lead to psychological and/or physical dependence. When a person is addicted to a drug, they might do bad or criminal acts in order to get money for more drugs, such as crimes (for example theft, robbery, fraud, or prostitution). If the person tries to stop using cocaine, they will go through cocaine withdrawal.