Welcome to the computer world. Practice materials for 1st year students. Еранина Т.И - 51 стр.

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Note

In some languages, one and a/an are the same word. In English,
a/an for the indefinite is more common. We use one if we want to
be precise, and we want to emphasize one, not two, or three, or
four.
     He drives a Volkswagen.
     She's got one Rolls-Royce, two
     Cadillac’s, and three motorbikes.

Definite article

The definite article is used
1 before seas, rivers, hotels, pubs, theatres, museums, and
   newspapers. (F)
      The Atlantic the British Museum
      The Times the Ritz
2 if there is only one. (G)
      the sun the Queen the Government
3 with superlative adjectives. (H)
       He's the richest man in the world.
       Jane's the oldest in the class.

Note

We do not use the with parts of the body. We use my/his/her/your,
etc.
        1 washed my hair.
        He broke his leg.
        Wrong He broke the leg.

No article

There is no article
1 before plural and uncountable nouns when talking about things
   in general. (I)
         I like potatoes.
         I like bread.
         Milk is good for you.
2 before countries, towns, streets, languages, magazines, meals,
    airports, stations, and mountains. (J)
         / had lunch with John.
         I bought Cosmopolitan at Padding ton Station.
3 before some places and with some forms of transport. (K)
           at home in/to bed at/to work