The power of PL/1 came from a well organized set of statements and types of variables that it supported. It FIRST INTRODUCED into language all three MAJOR classes of variables that are used in modern languages: static (like in Fortran common), automatic (allocated via stack, destroyed on EXIT from the procedure, and controlled (heap allocation).

It also contained some esoteric memory allocation features like areas of memory in which you can allocate your variables. Visibility was contolled by procedure scoping and there was SPECIAL class external variable that was exported in linked procedures (each variable was like separate common block in Fortran).

The power of PL/1 came from a well organized set of statements and types of variables that it supported. It first introduced into language all three major classes of variables that are used in modern languages: static (like in Fortran common), automatic (allocated via stack, destroyed on exit from the procedure, and controlled (heap allocation).

It also contained some esoteric memory allocation features like areas of memory in which you can allocate your variables. Visibility was contolled by procedure scoping and there was special class external variable that was exported in linked procedures (each variable was like separate common block in Fortran).