"There's an important difference here: Writing to a TTY which is stopped due to flow control, or due to lack of kernel buffer space, will block your process, whereas writing to a TTY from a background job will cause a SIGTTOU to suspend the entire process group. I don't know why the designers of UNIX had to go all the way to invent SIGTTOU and SIGTTIN instead of relying on blocking I/O, but my best guess is that the TTY driver, being in charge of job control, was designed to monitor and manipulate whole jobs; never the individual processes within them."
"There's an important difference here: Writing to a TTY which is stopped due to flow control, or due to lack of kernel buffer space, will block your process, whereas writing to a TTY from a background job will cause a SIGTTOU to suspend the entire process group. I don't know why the designers of UNIX had to go all the way to invent SIGTTOU and SIGTTIN instead of relying on blocking I/O, but my best guess is that the TTY driver, being in charge of job control, was designed to monitor and manipulate whole jobs; never the individual processes within them."
Can anyone provide any more insight about this?