Design and Implementation of the FreeBSD Operating System, The

Chapter 10. Terminal Handling

Historically, users interacted with the system using terminals connected to the computer through hardwired RS-232 serial lines. Although most computers still have one or two hardwired serial lines, their use is mostly relegated to running the system console, slow speed modems, serially connected printers, and similar devices. Although hardwired terminals are largely a footnote in history, the character processing done for keyboard I/O is still important.

The most common type of user session in FreeBSD uses a pseudo-terminal, or pty. The pseudo-terminal driver provides support for a device pair, termed the master and slave devices. The slave device provides to a process an interface identical to the one ...