In some operating systems, including Unix and Linux, a pseudoterminal, pseudotty, or PTY is a pair of pseudo-device endpoints (files) which establish asynchronous, bidirectional communication (IPC) channel (with two ports) between two or more processes. The master provides means by which a terminal emulator process controls the slave. The slave, emulates a hardware text terminal device. PTY are similar to bidirectional pipes. The master files are typically used by networking applications (e.g. rlogin) and slave files are used by terminal-oriented programs such as shells (e.g. bash) as a processes to read/write data back from/to master endpoint. Common application of PTYs is in providing network login services. Devpts is a Linux Kernel virtual file system used to emulate PTYs connection. Linux implementation is based on System V-style terminals (commonly referred as UNIX 98 pseudoterminals) and provides POSIX and the Single Unix Specification API in the form of a function since 1998. Unix command is typically used to get PTY file path connected to the current standard input. History Pseudoterminals were present in the DEC PDP-6 Timesharing Monitor at least as early as 1967, and were used to implement batch processing. They are described in the documentation for the succeeding TOPS-10 on the PDP-10. Other DEC operating systems also had PTYs, including RSTS/E for the PDP-11, as did the third-party TENEX operating system for the PDP-10. Implementations of Unix pseudo terminals date back to the modifications that RAND and BBN made to a 6th Edition in the late 1970s to support remote access over a network.<ref>[https://minnie.tuhs.org/cgi-bin/utree.pl?file=SRI-NOSC/dmr/pty.c ``PTY Driver for SRI-NOSC Net UNIX] lines 15-31</ref> Modern Unix pseudoterminals originated in 1983 during the development of Eighth Edition Unix and were based on a similar feature in TENEX. They were part of the 4.2 release of BSD, with a rather cumbersome interface defined for use. AT&T's System V included support for pseudoterminals as a driver in their STREAMS device model, along with the pseudoterminal multiplexer (). This later evolved to become the Unix98 style of PTYs. Books The Linux Programming Interface from 2010 contains an entire chapter (chapter 64 "Pseudoterminals" p1375–1399.) explaining pseudoterminals. Then there is another one, Chapter 62 "Terminals", dedicated to terminals. The Windows Console was extended to have a PTY interface called ConPTY in 2018. Applications The role of the terminal emulator process is: to interact with the user, to feed text input to the master pseudo-device for use by the