Portable Standard Lisp (PSL) is a programming language, a dialect of the language Lisp. PSL was inspired by its predecessor, Standard Lisp and the Portable Lisp Compiler. It is tail-recursive, late binding (or dynamically bound), and was developed by researchers at the University of Utah in 1980, which released PSL 3.1; development was handed over to developers at Hewlett-Packard in 1982 who released PSL 3.3 and up. Portable Standard Lisp was available as a kit containing a screen editor, a compiler, and an interpreter for several hardware and operating system computing platforms, including Motorola 68000 series, DECSYSTEM-20s, Cray-1s, VAX, and many others. Today, PSL is mainly developed by and available from Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB). Its main modern use is