Exercise can be fun, but it is important for the exerciser to do what he likes and eat enough calories , so when he exercises he is building up muscles, not just breaking them down for fuel. Carbohydrates are muscle-sparing; and if one does not get enough calories overall, there is the risk of burning muscles up with the fat to make up the deficit.
Benefits of exercise for all ages have been known since antiquity. Marcus Cicero, around 65 BC, stated: “It is exercise alone that supports the spirits, and keeps the mind in vigor.”
Regular exercise has been shown to help high blood pressure, obesity, heart disease, diabetes, and depression, among others. Exercise also helps people feel less tired.
Percentage
Percent means "out of one hundred". It is often shown with the symbol "%". It is used even if there are not a hundred items. The number is then scaled so it can be compared to one hundred. Percent is also used to indicate changes in numerical quantities.
For example, we have a bowl of fruit with three apples and one orange. The percentage of apples is 3 out of 4, or 3/4 = 75/100 = 75%.
A percentage is only one way of writing a ratio; one can also write it as a fraction or decimal. There are ways to convert fractions to percentages or decimals to percentages.
Percentages are useful in practice, because it allows one to compare things that are not out of the same number. For example, exam marks are often percentages, which can compare them even if there are more questions on one exam paper than the other.
Writing
Writing is the act of recording language on a visual medium using a set of symbols. The symbols must be known to others, so that the text may be read.
A text may also use other visual systems, such as illustrations and decorations. These are not called writing, but may help the message work. Usually, all educated people in a country use the same writing system to record the same language. To be able to read and write is to be literate.
Writing differs from speech because "the readers need not be present at the time". We can read writing from long ago, and from different parts of the world. Text stores and communicates knowledge. Writing is one of the greatest inventions of the human species. It was invented after people settled in towns, and after agriculture started. Writing dates from about 3,300, which is over 5000 years ago, in the Middle East.
Writing today is usually on paper, though there are ways to print on almost any surface. Television and movie screens can also display writing, and so can computer screens. Many writing materials were invented, long before paper. Clay, papyrus, wood, slate and parchment (prepared animal skins) have all been used. The Romans wrote on waxed tablets with a pointed stylus; this was popular for temporary notes and messages. The later invention of paper by the Chinese was a big step forward.
Writing is traditionally done using a hand tool such as a pencil, a pen, or a brush. More and more, however, text is created by input on a computer keyboard.
There are two schools of thought:
Therefore, depending on an author's definition of writing, the term may be used in different ways. With many early systems we do not know what they do convey. The central idea is that "a full writing system must be able to represent anything that might be said in spoken language". From this point of view the invention of the rebus is an essential step.
We can only be sure a sign system is full writing if we can translate the symbols into a modern language. In the case of some ancient scripts we cannot do this.
Writing was invented independently a number of times. The Sumerian, the ancient Egyptian, the Chinese and the Mayan writings are separate in their invention. All these writing systems started with "pictographs", symbols that stood for things. Then they developed a mixture of methods. Our own alphabetic system is different. It is based on the sounds of spoken language. All alphabets are modified versions of the first one, which originated with the Phoenicians and the Ancient Greeks.
The Sumerians lived in Mesopotamia, between the Tigris and Euphrates rivers. 5000 years ago this was a fertile region and is now mostly in Iraq. The Sumerians developed a form of writing called cuneiform. Triangular marks were pressed into soft clay tablets. After the clay had dried in the sun the tablets were baked. Then they were carried somewhere else for others to read. We know that its first uses were for trade, accounting and administration.
The earliest signs were mostly pictorial, but soon they stood as symbols for objects, ideas and sounds. This writing system was extremely successful, and outlasted the Sumerian empire. It was then used by other civilisations in the Middle East, such as the Old
Akkadian, Babylonian, Assyrian, Elamite, Hittite, Old Persian and Ugaritic empires. The last cuneiform inscription was dated as 75. Thus the system had lasted for more than 3000 years. Each version of cuneiform had to be deciphered separately, because all the languages were different. Documents (including stone objects) written in more than one language provided the clues.
This is the most famous of the old forms of writing, or "scripts". It was invented at roughly the same time as cuneiform, yet was quite different in style, and used different materials. Egyptians ended up with three writing systems for the same language. They were:
The writing tools used varied according to the material which was written on. The two cursive scripts were written with reed pens and carbon inks onto papyrus. If the material was cloth, then the writing was done by a brush. Many examples survive. The hieroglyphs were inscribed (carved) into stone (hammer & chisel) or painted onto stone surfaces. Many survive, some with the original colours intact. The key event in the decipherment of hieroglyphic writing was the discovery of the Rosetta Stone. This is a granite slab with the same message written in hieroglyphic, demotic and in Greek. Ancient Greek is well understood, and made possible the interpretation of the other two scripts.
Chinese is the language with the largest number of native speakers. Its history dates back to about 1400. The Chinese writing system is idio-syllabic, a mixed method using characters which may have one or more of these elements:
Chinese has a huge number of characters: in the region of 50,000. Because of this, printing methods were never really successful in China, despite their early invention. In the 14th century Wang Tzhen had sixty thousand wood block characters cut, a huge investment in time and money. He printed 100 copies of a local gazette, and was author of a treatise on agriculture and other technical works. Even with printing machines from Europe in the 19th century, the process was hampered by the huge number of characters, which slowed the "composition" to a snail's pace.
China has eight regional languages that are mutually unintelligible, and many true dialects. The system appears to work mainly because as many as 70% speak Mandarin. Fluency in Chinese reading and writing is undoubtedly difficult to achieve, and this must act as a brake on the drive for literacy. There have been a number of attempts to reform or simplify the system. The most radical in Pinyin, which is a program to replace Chinese characters with an alphabetic system. This was supported by Mao, but faltered after his death.
It seems that the idea of an alphabet–a script based entirely upon sound–arose only once, and has been copied and adapted to suit many different languages. Although no alphabet fits its language perfectly, it is flexible enough to fit any language approximately. It was a unique invention.