Error-Detecting Code and ASCII Character Code?
Parity bits are added, checked and removed by communications devices (COM ports) at a hardware level.

If you are interacting with a hardware device that expects 7 bit characters, often the interface will be 8 bit and the parity bit will be available on reading, but should be ignored. Using interfaces at this level, will only allow 7 bit characters to be transmitted - and ASCII is a 7 bit code. 

If you need to transmit larger character codes - e.g. Unicode (which can be up to 32 bits), there are many encoding schemes like UTF-8 that specify how larger numbers will be broken down into smaller values which can then be transmitted by the hardware. 

An example scheme to transmit 8 bit codes over a 7 bit interface, breaks the 8 bit characters into multiple 7 bit characters for transmission over the hardware. e.g. values 1-127 may be transmitted as is, 128-255 may be transmitted as 0 followed by 0 to 127, and 0 transmitted as three 0's