Software is rife with unknown unknowns - situations you think you understand at the outset only to discover that the problem is different from your first impressions (and typically much harder).

软件开发充满了尚未意识到的未知数—通常会有这种情况，您认为您在开始的时候已经理解了，却发现问题不同于您的第一印象(通常更复杂)。

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The first day using any software is very different from what it's like day-in and day-out after extended use, but first impressions are important to make note of.

第一天使用软件和平常使用软件非常不同，但是第一印象很重要。

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Overall the first impressions of Android coming from three years as an iPhone user were not too good.

总的来说，Android的第一印象来自于三年来作为iPhone用户感觉并不是太好。

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First impressions of the new Pope from the faithful on St Peter's Square have been favourable.

BBC: Pope Francis: St Peter's crowds hear Angelus prayer

At a time when the international book bazaar is flooded with offerings from India by eager, first-time novelists on a mission to alter the impressions left by Kipling and Naipaul, Seth here makes no attempt to flaunt his Indian-ness.

CNN: ASIANOW - TIME Asia

Poor first impressions, for starters, can cause job seekers to eliminate the employer from consideration altogether.

FORBES: Treating Job Applicants Badly May Cost Employers Later On