crc

2 definitions found

crc - Free On-line Dictionary of Computing (26 May 2007) :

  cyclic redundancy check
  CRC
  cyclic redundancy code
  
     <algorithm> (CRC or "cyclic redundancy code") A number derived
     from, and stored or transmitted with, a block of data in order
     to detect corruption.  By recalculating the CRC and comparing
     it to the value originally transmitted, the receiver can
     detect some types of transmission errors.
  
     A CRC is more complicated than a checksum.  It is calculated
     using division either using shifts and exclusive ORs or
     table lookup (modulo 256 or 65536).
  
     The CRC is "redundant" in that it adds no information.  A
     single corrupted bit in the data will result in a one bit
     change in the calculated CRC but multiple corrupted bits may
     cancel each other out.
  
     CRCs treat blocks of input bits as coefficient-sets for
     polynomials.  E.g., binary 10100000 implies the polynomial:
     1*x^7 + 0*x^6 + 1*x^5 + 0*x^4 + 0*x^3 + 0*x^2 + 0*x^1 + 0*x^0.
     This is the "message polynomial".  A second polynomial, with
     constant coefficients, is called the "generator polynomial".
     This is divided into the message polynomial, giving a quotient
     and remainder.  The coefficients of the remainder form the
     bits of the final CRC.  So, an order-33 generator polynomial
     is necessary to generate a 32-bit CRC.  The exact bit-set used
     for the generator polynomial will naturally affect the CRC
     that is computed.
  
     Most CRC implementations seem to operate 8 bits at a time by
     building a table of 256 entries, representing all 256 possible
     8-bit byte combinations, and determining the effect that each
     byte will have.  CRCs are then computed using an input byte to
     select a 16- or 32-bit value from the table.  This value is
     then used to update the CRC.
  
     Ethernet packets have a 32-bit CRC.  Many disk formats
     include a CRC at some level.
  
     (1997-08-02)
  

crc - V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006) :

  CRC
         Cyclic Redundancy Check[sum]