Even and Odd Parity,

10010001 is even parity how if we count the 1s that  is 3 which is not even if 0s its also 5 which no even what is the meaning of even here.
10010111 is called odd how?

In communications, parity checking refers to the use of parity bits to check that data has been transmitted accurately. The parity bit is added to every data unit (typically seven or eight bits ) that are transmitted. The parity bit for each unit is set so that all bytes have either an odd number or an even number of set bits.

Odd parity:

The number of 1-bit must add up to an odd number.

Even parity:

The number of 1-bit must add up to an even number

Suppose you receive a binary bit word “0101” and you know you are using an odd parity.Is the binary word error? The answer is yes: There are 2 1-bit, which is an even number.We are using an odd parity.So there must have an error.

A single bit is appended to each data chunk for making the number of 1 bits even/odd

Example: even parity

1000000(1)

1111101(0)

1001001(1)

Example: odd parity

1000000(0)

1111101(1)

1001001(0)

Assume we are using even parity with 7-bit ASCII. The letter V in 7-bit ASCII is encoded as 0110101.How will the letter V be transmitted? Because there are four 1s (an even number), parity is set to zero. This would be transmitted as: 01101010.If we are using an odd parity: The letter V will be transmitted as 01101011.