I read this on a another forum but couldn't figure out the logic behind the answers.

He had been typing for three hours before he realised that he had typed the wrong documents.

He had been typing for three hours before he realised that he typed the wrong documents.

He was typing for three hours before he realized that he typed the wrong documents.

Could anyone explain what the difference between these three statements are?

  • 1
    Isn't the third one just grammatically wrong?
    – Bidella
    Mar 2, 2012 at 4:09
  • The second one looks odd to me; I thought it was going to say "He had been typing for three hours before he realised that he was typing the wrong documents."
    – Henry
    Mar 2, 2012 at 8:12
  • 2
    Just so nobody gets the wrong impression, there are lots of correct ways to say this in English. For example: "He typed for three hours before he realized he was typing the wrong documents." The last two are incorrect because in "he realized that he typed", you cannot put the second verb in the simple past. Mar 2, 2012 at 11:23

2 Answers 2


Only the first is a possible English sentence. There are three events described here: ‘typing for three hours’, ‘typed the wrong documents’ and ‘he realised’. The first two happened at roughly the same time, and are therefore written with a past perfect construction. The first uses ‘had been’ + the –ing form of ‘type’ to show progressive aspect, because the typing is seen as continuing over a period of time. The second uses ‘had’ + the past participle of ‘type’ to show perfective aspect, because typing the wrong documents is seen as a complete event. The third event is expressed in the past tense, ‘he realised’, because it is seen as a complete event that occurred at a specific time in the past, but after the other two events.

In the second sentence, ‘he typed the wrong documents’ doesn’t work because the use of the past tense there places the event in the same time frame as ‘he realized’, which clearly happened after the typing, not at the same time as the typing.

The third sentence is almost possible, but there the past tense, ‘typed’, also gets the timing wrong. Typing the wrong documents happened before the realization of what had happened, and so needs a construction that expresses that prior occurrence. What is called for, therefore, is ‘he had typed the wrong documents.’

  • In the last sentence, if we convert 'typed' to past perfect as you described don't we have to do the same to the 'was typing' part? And if we leave it as it is, what would be the difference with the past perfect then?
    – Noah
    Mar 2, 2012 at 9:38
  • @Noah: ‘He was typing’ describes a past event continuing over time. That event coincides with the fact that the documents being typed were the wrong documents. The realization of that fact comes only after the mistake has been made. ‘Had typed’ expresses that sequence of events in a way that ‘typed’ doesn’t. It is, however, legitimate to ask what the difference is between ‘he was typing’ and ‘he had been typing’. The answer to that lies in the timing shown in the rest of the passage, to which we do not have access in this extract. Mar 2, 2012 at 9:54
  • You could say: "He was typing for three hours before he realized that he typed the documents incorrectly." It is correct grammatically. If I were to read it, I would assume that he was physically typing wrong (as in, the act of typing/input was not done in the way they were supposed to).
    – Tucker
    Aug 7 at 10:56

The 1st statement seems okay to me. I fathom, each of the above statement varies in the usage of the past tense. The 1st one uses past perfect continuous tense. The 2nd statement tries to use the same but it is incorrect usage. The 3rd statement tries to use past continuous but again incorrectly. It should have been:He was typing for three hours before he realized that he was typing the wrong documents. When you use the Past Continuous with two actions in the same sentence, it expresses the idea that both actions were happening at the same time. The actions are parallel.

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