Editing XPL (section)

==Language==
The XPL language is a simple, small, efficient dialect of [[PL/I]] intended mainly for the task of writing compilers.  The XPL language was also used for other purposes once it was available.  XPL can be compiled easily to most modern machines by a simple compiler.  Compiler internals can be written easily in XPL, and the code is easy to read.  The PL/I language was designed by an [[IBM]] committee in 1964 as a comprehensive language replacing [[Fortran]], [[COBOL]], and [[ALGOL]], and meeting all customer and internal needs.  These ambitious goals made PL/I complex, hard to implement efficiently, and sometimes surprising when used.  XPL is a small dialect of the full language.  XPL has one added feature not found in PL/I: a [[string (computer science)|STRING]] datatype with dynamic lengths.  String values live in a separate text-only [[heap (data structure)|heap]] memory space with automatic [[garbage collection (computer science)|garbage collection]] of stale values.  Much of what a simple compiler does is manipulating input text and output byte streams, so this feature helps simplify XPL-based compilers.