I am going to write an e-mail to Tom. His address is tom@email.com. Or is it tom@email.net? 

You can discover what your enemy fears most by observing the means he uses to frighten you. (Eric Hoffer) 

In 1969 the price of 5 kg of flour was $0.75. In 1970 the price was increased 15% to $0.86. In 1971, the 1970 price was decreased by 5%. What was the price of 5 kg of flour in 1971? $0.82, right? 

If you don't like typing the @ or & symbols, you can set up an auto-correct function to change "at//" into @ and "an//" into &. 

In the IRC protocol, @ is the symbol for a channel operator. IRC also uses the user@host form for identifying and banning users. 

Default mode switching can be achieved by pressing [mode] + [shift] with a key-press chord. 

The ampersand & is often, although not necessarily correctly, used, but really it should never be used in formal texts. Instead of writing "Cats & dogs" write "Cats and dogs." 

Square brackets [these] are mainly used in computer programming and to insert a clarifying word or phrase into a quotation. Example: "[P.D. James' fictional detective] Dalgleish is both a poet and a policeman." 

Stephanie had $40. Her mother gave her another $30 and her aunt $10 to buy a shirt. The one Stephanie wants costs $54.99. If she got a 20% discount, how much would it cost? 

"Why I came here, I know not; where I shall go it is useless to enquire - in the midst of myriads of the living & the dead worlds, stars, systems, infinity, why should I be anxious about an atom?" (Lord Byron) 

Chinese calligraphy has acquired western symbols, including $ and @, although linguistic purists resist this trend vigorously. 

Psychologists have found that short hand symbols such as $ and & are not as difficult for dyslexic patients to read as normal text. 