Hi I wanted to know if there are any instruction that modify the UART buffer other than those in the serial library, in particularly if digitalread or write use the buffer.
Also if I use Serial.print the information to send in output are stored in the buffer or not?
You can't use digitalRead to read a memory buffer, and using it write anything makes no sense at all.
Serial input and output buffers are completely separate areas of memory.
No I wanted to know if digitalread and digitalwrite modify when used
digitalRead doesn't change anything.
digitalWrite will change the state of a pin or register if the value written is different to the value already there.
Neither has anything to do with a value in a memory buffer.
What do you mean "modify"? You want to scramble characters before Serial.read() sees them?
We need more information to clarify the question. What do you want to do? Don't tell us how you want to do it, just what are the desired inputs and outputs.