Source : Free On-Line Dictionary of Computing

PL/I
     
        Programming Language One.
     
        An attempt to combine the best features of {Fortran}, {COBOL}
        and {ALGOL 60}.  Developed by George Radin of {IBM} in 1964.
        Originally named NPL and Fortran VI.  The result is large but
        elegant.  PL/I was one of the first languages to have a formal
        {semantic} definition, using the {Vienna Definition Language}.
        {EPL}, a dialect of PL/I, was used to write almost all of the
        {Multics} {operating system}.  PL/I is still widely used
        internally at {IBM}.  The PL/I standard is ANS X3.53-1976.
     
        PL/I has no {reserved word}s.  Types are fixed, float,
        complex, character strings with maximum length, bit strings,
        and label variables.  {Array}s have lower bounds and may be
        dynamic.  It also has summation, multi-level structures,
        {structure assignment}, untyped pointers, {side effect}s and
        {aliasing}.  {Control flow} constructs include goto; do-end
        groups; do-to-by-while-end loops; external procedures;
        internal nested procedures and blocks; {generic procedure}s
        and {exception handling}.  Procedures may be declared
        {recursive}.  Many implementations support {concurrency}
        ('call task' and 'wait(event)' are equivalent to {fork}/join)
        and compile-time statements.
     
        {LPI} is a PL/I {interpreter}.
     
        ["A Structural View of PL/I", D. Beech, Computing Surveys, 2,1
        33-64 (1970)].
     
        (1994-10-25)