Origin/purpose of katakana

Konnichi wa , minasan.
This is about the origin of Katakana.
I have referred various sites, but none seem to give a decent explanation of why, how and when katakana was devised.
Can anyone throw some light on this?

One thing that strikes me is this -
English has thousands of borrowed words, but over a period of time, learners of the language can never distinguish between original english words and borrowed ones. (there are too many borrowed from too many languages written in the same script)
But, though Japanese too inducts an alarming number of gairaigo (foriegn words) into its vocabulary, I think the native vocabulary is kind-of protected by writing gairaigo in katakana.
Say, a Japanese sees a foriegn word 500 years hence, he can say by looking that its a gairaigo, since its written in katakana.

Was this division made to clearly demarcate foriegn words?
I mean, was the concept of 'soto' and 'uchi' applied here as well when katakana was invented?
akumademo, 'wago' wa 'uchi' to 'gairaigo' wa 'soto' to hakkiri to wakeru suru tame 'katakana' to iu moji ga sakusei sareta deshouka?

Of course, Katakana is also used to write names of flowers, plants etc. but I think this is a much later coincidental development.

Or am I off the mark here?

Katakana is used for foreing word exactly. Nowadays, Japanese people like to use Katakana very often, because they think Katakana look COOL more than Kanji or Katakana. Especially at many advertisement, food's name, magazines....people feels more familier if they read Katakana or Hiragana on those products.

Japanese people like to make new words a lot, then they forget very soon. And they are temporary fashion. Maybe tomorrow, they will think Kanji is much cool than Katakana or Kanji, because they think Katakana is not cool anymore. That will be happened, I think.

A lot of Japanese people are complaining that Japanese mass madia uses Katakana too much. Especially, old people doesn't understand what they are talking and writing about, since they were not educated well about English. I don't like that people write strange "Japanese English" either. I think they sounds very SILLY. The one of big reason why Japanese people doesn't speak good English, because they made up strange English with Katakana letters. That makes people learning English confused very very much.

For academic things (plants, animals...), they use Katakana as you pointed. I don't know why.

Anyway, if you learn Japanese. you shouldn't think about those temporality fashion words. Those words will soon disappered. Should learn proper JApanese language with good text books.

Hi all. I think I may have a more accurate explanation to your interrogation, even if many of the things expressed above are true.

The character in Chinese texts brought to Japan through Korea at the beginning of the 4th century gradually came to be adopted by the Japanese for the writing of their own language, for which there was no native system of writing at the time.

Now, the Chinese characters were used phonetically to represent similar-sounding Japanese syllables--the meanings of the characters were more often than not ignored. In this way, one could represent phonetically any Japanese word. But because each Chinese character only corresponds to one syllable, it was necessary to use many characters to write multisyllabic words, which frequently involved a large number of brush strokes.

To simplify this bothersome process, instead of the full angular style of writing (kaisho 楷書; box writing), a simplified derivative writing style was devised (sousho 草書; cursive writing). It came to be believed that the sousho style suited the Japanese litterary notation better.

Toward the end of the Nara period (710-794) and during the Heian period (794-1185) the sousho style underwent further simplification, in which esthetics played some part, resulting in a stock of phonetic characters extensive enough to represent the entire phonetics of the Japanese language. This was the decisive step towards the establishment of a purely phonetic character system representing syllables. These simple syllable characters are known today as hiragana, but were then formerly referred to as "onna-de" or ladies' hand because they were first used by women of the Heian period in letters and literary writing, who were supposed to be ignorant of the exclusively male domain of Chinese learning, literature, and writing. However, over time, hiragana came to prevail as the dominant syllabary.

Katakana was developped a little later, but not much. While listening to lectures on the classics of Buddhism, students wrote in their texts notations on the pronounciatation of meanings of unfamiliar characters, and sometimes wrote commentaries between the lines of certain passages. This practice required the use of some sort of phonetic shorthand, which led in turn to the development of katakana.

Like hiragana, katakana is based on Chinese characters corresponding to particular syllables. However, unlike hiragana, which is a cursive simplification of kanji, the more angular katakana were developped taking only single components of kanjis of the kaisho style.

Because katakana was closely associated with science and learning, this syllabary was for a long time exclusively used by men.

The selection of hiragana and katakana in use today was laid down in 1900 in a decree for elementary schools. Some obsolete symbols such as we ゑ, ヱ, and wi ゐ, ヰ were dropped during reforms after WWII. As a result we have 46 kana recognized today.

As this brief (yeah, right!) explanation implies, katakana was strongly associated with science and learning, which is why it is found very often in botany and marine sciences, often replacing seldom used and/or overly cumbersome kanji, so no, not all katakana words are gairaigo.

As for the tendency of Japanese to katakanize foreign words, read the following thread.

NYT arcticle on English loan words | Japan Forum