I am new to German so would would be grateful if someone could help with this trivial question.
When doing some exercises from my course book I saw such example
Der Computer ist nicht neu. Es ist ein alter Computer.
The question is why in the second sentence they use "es ist" instead of "er ist".
Also there were some examples for feminine and neutral nouns as well (die Uhr, das Bild) and all of them used "es ist" in the second sentence.
'Es' can refer back to a non-neuter or plural noun, as an alternative to the expected masculine, feminine, or plural pronoun:
-Siehst du die Kinder dort? Es/Sie sind meine
-Seine Mutter lebt noch. Es/Sie ist eine alte Frau
'Es' can as well be used in this sense with a plural verb and corresponds to 'they':
-Es sind Ärzte.
-Was sind es?
'Es' can as well be used with personal pronouns:
-Du bist es.
-Seid ihr es gewesen?
Also in a cleft sentence:
-Er war es, der es mir sagte.
-Du warst es also, der geklingelt hat.
