What is Parity: Definition and 220 Discussions

A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), although they can also be applied separately to an entire message string of bits.
The parity bit ensures that the total number of 1-bits in the string is even or odd. Accordingly, there are two variants of parity bits: even parity bit and odd parity bit. In the case of even parity, for a given set of bits, the occurrences of bits whose value is 1 are counted. If that count is odd, the parity bit value is set to 1, making the total count of occurrences of 1s in the whole set (including the parity bit) an even number. If the count of 1s in a given set of bits is already even, the parity bit's value is 0. In the case of odd parity, the coding is reversed. For a given set of bits, if the count of bits with a value of 1 is even, the parity bit value is set to 1 making the total count of 1s in the whole set (including the parity bit) an odd number. If the count of bits with a value of 1 is odd, the count is already odd so the parity bit's value is 0. Even parity is a special case of a cyclic redundancy check (CRC), where the 1-bit CRC is generated by the polynomial x+1.
If a bit is present at a point otherwise dedicated to a parity bit but is not used for parity, it may be referred to as a mark parity bit if the parity bit is always 1, or a space parity bit if the bit is always 0. In such cases where the value of the bit is constant, it may be called a stick parity bit even though its function has nothing to do with parity. The function of such bits varies with the system design, but examples of functions for such bits include timing management or identification of a packet as being of data or address significance. If its actual bit value is irrelevant to its function, the bit amounts to a don't-care term.

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  1. L

    The concept of parity and it's significance

    Hi, I am revising my intro to nuclear physics class and was wondering why is parity so important ? I mean OK, I get it, physicists are crazy about symmetries, but I do not understand what does it physically mean... I was wondering if someone could possibly talk me through its importance and...
  2. J

    Understanding the Intrinsic Parity of Quarks and Antiquarks

    A quark and antiquark have opposite parity. The quark is customarily taken to have positive parity. I understand this to mean that Pf = f, where f is the wavefunction of the quark and Pg = -g, where g is the wavefunction of the antiquark. Does this mean that P acting on an antiquark...
  3. J

    Parity violation in weak decays

    I am confused about when and to what extent parity is violated in weak decays. On the one hand, there's Wu's famous experiment where electrons are emitted preferentially in one direction. This parity violation can be said to be maximal, since all electrons are emitted in one direction...
  4. J

    Parity violation in weak decays

    Homework Statement I am confused about parity violation in weak decays. I learned about Wu's famous experiment and how it demonstrates that parity is violated in weak decays. However, when I am doing a course problem on nuclear β-decay, then it still necessary to conserve parity...
  5. J

    What is the significance of parity in particle physics?

    The parity operator has eigenvalues of +/- 1 and particles can have intrinsic parity of +/- 1. What does it matter? Does a P=-1 particle behave physically different from a P=+1 particle? Is parity a useful concept only in the sense that one can check if an interaction conserves parity (parity...
  6. S

    Parity Violation in Weak Decay

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  7. F

    Does Parity Checking Have Any Real Value in Error Detection?

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  8. T

    Parity of a Particle (and Parity of the Higgs in particular)

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  9. L

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  10. C

    Parity Exchanges Right & Left-Handed Spinors: Q&A from Page 94 of Tong's QFT

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  11. R

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  12. X

    Quantum Mechanics: Parity Problem

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  13. B

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  14. V

    Why do the X, Y, Z operators switch parity?

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  15. W

    The conservation of parity and time reversal

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  16. K

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  17. Amith2006

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  18. C

    Understanding parity and parity conservation

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  19. L

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  20. E

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  21. V

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  22. D

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  23. D

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  24. Z

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  25. C

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  26. H

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  28. H

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  29. N

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  30. A

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  31. T

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  32. C

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  33. A

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  34. N

    Classic problems about parity property

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  35. J

    Do anti-particles have opposite parity?

    Hi, I understand that anti-particles have the opposite charge to particles. Do anti-particles have the opposite parity to particles as well? John
  36. U

    What Determines the Parity of Deuteron Spin and Parity?

    Deuteron is given by j(p)=1(+) In my textbook it says that the observed parity of + for deuteron means that the orbital angular momentum quantum number, l, is even so is 0 or 2, and s=1. However, looking back the textbook also says that for odd-odd nuclei, the parity is given by the...
  37. B

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  38. R

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  39. M

    Parity Violation of Weak Force - Wu et al.

    I have read about Wu et al. and their experiments with Co 60 that showed that the weak interaction violates parity. I don't quite get it tho. 6 So they aligned Co atoms in a magnetic field. Some of the nuclei decay and emit neutrinos and electrons. It was observed that an equal number of the...
  40. M

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  41. bcrowell

    Incorrect explanation of parity violation?

    This APS page http://focus.aps.org/story/v22/st19 describes the classic experiment by Wu et al. in the 50's that demonstrated parity violation. It contains the following explanation: "[1] The magnetism of the nuclei can be thought of as resulting from their spin. With the nuclei aligned with...
  42. L

    Predicting Nuclear Parity & Spin: 14N, 20F, 24Na and 26Al

    1. Use the shell model to predict the nuclear parity and range of possible values for nuclear spin for 14N, 20F, 24Na and 26Al. Compare witht he actual parities and spin 2. J = Jn + Jp pi = (-1)^l The Attempt at a Solution I've done out all of them, I got the theoretical values...
  43. U

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  44. W

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  45. S

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  46. O

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  47. C

    What is the role of parity in quantum mechanics?

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  48. J

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  49. S

    Helicity, Chirality, and Parity Violation

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  50. C

    Parity - Particle In A Box (Infinite Potential)

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