Chapter Four goes into how the manipulation of history/reality is done.
How lies the government told the public, the mistakes made in Big Brother’s broadcasts, were ‘corrected’. How documents were changed to match now.
Winston would receive his instructions in ‘newspeak’ and know which document to pull, what corrections to be made, then push the instructions and the original documents into a tube to be sent to an incinerator.
…”Winston’s greatest pleasure in life was in his work. Most of it was a tedious routine, but included in it there were also jobs so difficult and intricate that you could lose yourself in them as in the depths of a mathematical problem — delicate pieces of forgery in which you had nothing to guide you except your knowledge of the principles of Ingsoc and your estimate of what the Party wanted you to say. Winston was good at this kind of thing. On occasion he had even been entrusted with the rectification of ‘The Times’ leading articles, which were written entirely in Newspeak.”
Newspeak was a kind of clipped language in which one had to be fluent in the language to appreciate what was ordered.
Although Newspeak, used in this chapter seemed a special secret way of communication, in today’s world, this kind of language is often been used to segregate and limit a population.