Asked by: Lillian Guainiere, Rye

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Computer files are stored as lots of ones and zeros. An ordinary delete operation will either just move the file to a new area called ‘Trash’, or it may make the computer forget where the file is, without removing the file. Even reformatting a drive may not work because it’s like removing the table of contents in a book – all the pages of words are really still there. You may need special software to permanently delete files. This software will overwrite those pesky ones and zeros, setting them all to zero or to random values. When you’ve done that to a file, it ceases to exist, and the data is gone forever.


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Authors

Dr Peter Bentley is a computer scientist and author who is based at University College London. He is the author of books including 10 Short Lessons in Artificial Intelligence and Robotics and Digital Biology: How nature is transforming our technology and our lives.

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