SAIL, the Stanford Artificial Intelligence Language, was developed by Dan Swinehart and Sproull of the Stanford AI Lab in 1970. It was originally a large ALGOL 60-like language for the DEC-10 and DEC-20.

SAIL's main feature is a symbolic data system based upon an associative store (originally called LEAP). Items may be stored as unordered sets or as associations (triples). Other features include processes, events and interrupts, contexts, backtracking and record garbage collection. It also has block-structured macros, a coroutining facility and some new data types intended for building search trees and association lists.

A number of interesting software systems were coded in SAIL, including early versions of FTP and TeX and a document formatting system called PUB.

In 1978, there were half a dozen different operating systems for the PDP-10: WAITS (Stanford), ITS (MIT), TOPS-10 (DEC), CMU TOPS-10 (CMU), TENEX (BBN), and TOPS-20 (DEC, after TENEX).

SAIL was ported from WAITS to ITS so that MIT researchers could make use of software developed at Stanford University. Every port usually required the rewriting of I/O code in each application.