I found some examples of hiragana, katakana and kanji from newspaper, magazines and shops and advertisements.
For the Katakana, it can be used as loan words and emphasized words.
Loan words :
Char Siu (barbecued pork) : チャーシュー
Wine : ワイン
America : アメリカ (country name)
America : アメリカ (country name)
Emphasized words :
サイコー
I found this on a post. Usually, we write さいこう instead of サイコー. It uses サイコー because the author want to emphasize that the influence of The Analects of Confucius(論語).
I found that a post use hiragana as onomatopoeia.
Onomatopoeia : みゃ~みゃ~
It is the sound of cats.
Hiragara can also used to show the main subject.
In this case, こども is written. The advertisement probably want to stick out the word "children". Hence, "子供" is not used. If "子供" is used, there will be many kanji exsisting in the title. I t may make the readers feel confused.
There is a menu with Japanese shown outside the shop. The restaurant owner may want to attract some Japanese living there.
"Fujitsu" is romaji and is the brand name of the computer. It also allows people to read it. If customers do not understand Japanese, they are not able to pronounce the word in hiragana or katakana.
Hence, Romaji is convenient for foreigners ro pronounce the words.
Hence, Romaji is convenient for foreigners ro pronounce the words.