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dd (Unix)
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<p>dd is <a href="/facts/Shell_(computing)/Sa67elS7">shell</a> <a href="/facts/Command_(computing)/zUrvQbFy">command</a> for reading, writing and converting <a href="/facts/Computer_file/FjFH3Ufm">file</a> <a href="/facts/Data/AUBFN97o">data</a>. Originally developed for <a href="/facts/Unix/0pNL2seI">Unix</a>, it has been ported to many other <a href="/facts/Operating_system/8XTuvMh2">operating systems</a> (OSs) including <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> OSs, <a href="/facts/Microsoft_Windows/bwhAhuSL">Windows</a>, <a href="/facts/Plan_9_from_Bell_Labs/pQjPlS7w">Plan 9</a> and <a href="/facts/Inferno_(operating_system)/baKPoWRU">Inferno</a>. </p><p>The command can be used for many purposes. For relatively simple copying operations, it tends to be slower than domain-specific alternatives, but it excels at overwriting or truncating a file at any point or seeking in a file. </p><p>The command supports reading and writing files, and if a <a href="/facts/Device_driver/rDYnHU1G">driver</a> is available to support file-like access, the command can access devices too. Such access is typically supported on Unix and similar OSs that tend to provide file-like access to devices (such as <a href="/facts/Computer_data_storage/wPHKFpdx">storage</a>) and special <a href="/facts/Device_file/t8ISnXft">device files</a> (such as <a href="/facts/%2fdev%2fzero/C8EFYqYx">/dev/zero</a> and <a href="/facts/%2fdev%2frandom/o7Xrsrcw">/dev/random</a>). Therefore, the command can be used for tasks such as backing up the <a href="/facts/Boot_sector/YubeSECp">boot sector</a> of a drive, and obtaining random data. </p><p>The command can also support converting data while copying; including <a href="/facts/Byte_order/wbrQnyu3">byte order</a> swapping and converting between <a href="/facts/ASCII/vGUI33Qu">ASCII</a> and <a href="/facts/EBCDIC/qAhmvgj0">EBCDIC</a> text encodings. </p>