Most serial devices support five parity settings. Only two of the settings can be used to perform a parity check.

- Odd
- Even
- Space
- Mark
- None

### Odd Parity

Odd parity is the original parity checking system first put into use by IBM. Odd parity attempts to maintain an odd number of ones in each byte. When a byte has an odd number of ones, the value of the parity bit is zero. When the number of ones in the byte is even, a single bit is added with the value of one, making the number of ones, odd.

### Even Parity

Even parity, a variation on odd parity, also provides a means for detecting errors. Even parity attempts to maintain an even number of ones in each byte. When there are an even number of 1-bits, the value of the parity bit is zero. When there are an odd number of 1-bits, the value of the parity bit is 1, making the number of bits an even count of 1-bits.

### Space Parity

Space parity sets the parity bit to zero for all bytes/words, effectively disabling any parity checking mechanism in use. Space parity is not actually a parity checking method, it is a method used to disable parity checking.

### Mark Parity

Systems utilizing *mark parity* set the parity bit to one for all bytes/words, effectively disabling the parity checking. Mark parity is not actually a parity checking method, it is a method used to disable parity checking.

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