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Self-synchronizing code
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<p>In <a href="/facts/Coding_theory/SBqStoGL">coding theory</a>, especially in <a href="/facts/Telecommunications/vxoj1cxR">telecommunications</a>, a self-synchronizing code is a <a href="/facts/Uniquely_decodable_code/DImYG6eg">uniquely decodable code</a> in which the <a href="/facts/Symbol_(data)/YlQ3JHVr">symbol</a> stream formed by a portion of one <a href="/facts/Code_word_(communication)/sASREopJ">code word</a>, or by the overlapped portion of any two adjacent code words, is not a valid code word. Put another way, a set of strings (called "code words") over an alphabet is called a self-synchronizing code if for each string obtained by concatenating two code words, the substring starting at the second symbol and ending at the second-last symbol does not contain any code word as substring. Every self-synchronizing code is a <a href="/facts/Prefix_code/461neBYx">prefix code</a>, but not all prefix codes are self-synchronizing. </p><p>Other terms for self-synchronizing code are synchronized code or, ambiguously, comma-free code. A self-synchronizing code permits the proper <a href="/facts/Frame_synchronization/uCRQnA4J">framing</a> of transmitted code words provided that no uncorrected errors occur in the <a href="/facts/Data_stream/57yDhBCd">symbol stream</a>; external <a href="/facts/Synchronization/L39sYwbr">synchronization</a> is not required. Self-synchronizing codes also allow recovery from uncorrected errors in the stream; with most prefix codes, an uncorrected error in a single <a href="/facts/Bit/S972NSaD">bit</a> may propagate errors further in the stream and make the subsequent data <a href="/facts/Data_corruption/b5j3bISU">corrupted</a>. </p><p>Importance of self-synchronizing codes is not limited to <a href="/facts/Data_transmission/1yAhaANd">data transmission</a>. Self-synchronization also facilitates some cases of <a href="/facts/Data_recovery/KvNG11I1">data recovery</a>, for example of a <a href="/facts/Character_encoding/ShJHIMoA">digitally encoded text</a>. </p>