A ''hex dump'' is a listing of memory contents in HexaDecimal.  The format of the output usually looks something like this:

 00000000:  09 A6 00 00 7F 36 32 30  .....620
 00000008:  31 36 31 37 30 00 00 00  16170...
 00000010:  00 00 00 00 01 30 30 30  .....000
 00000018:  38 39 31 20 20 20 20 20  891.....

The leftmost column gives the memory address (or offset from wherever the dump started), the hex digits are in the middle, then on the right is an ASCII representation of the bytes (with '.' used for non-printing characters).  The number of bytes shown per row is usually 8 or 16.

Hex dumps are invaluable for low-level debugging, particularly for low-level communications between devices.  Many applications and libraries have hex-dump capabilities built in for debugging or diagnostics.

See also HexDumpInManyProgrammingLanguages
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CategoryDebugging