68 Chapter 2 Evolution of the Major Programming Languages
2.8 Everything for Everybody: PL/I
PL/I represents the first large-scale attempt to design a language that could
be used for a broad spectrum of application areas. All previous and most sub-
sequent languages have focused on one particular application area, such as
science, artificial intelligence, or business.2.8.1 Historical Background
Like Fortran, PL/I was developed as an IBM product. By the early 1960s, the
users of computers in industry had settled into two separate and quite dif-
ferent camps: scientific and business. From the IBM point of view, scientific
programmers could use either the large-scale 7090 or the small-scale 1620 IBM
computers. This group used floating-point data and arrays extensively. Fortran
was the primary language, although some assembly language was also used.
They had their own user group, SHARE, and had little contact with anyone
who worked on business applications.
For business applications, people used the large 7080 or the small 1401
IBM computers. They needed the decimal and character string data types, as
well as elaborate and efficient input and output facilities. They used COBOL,
although in early 1963 when the PL/I story begins, the conversion from assem-
bly language to COBOL was far from complete. This category of users also
had its own user group, GUIDE, and seldom had contact with scientific users.
In early 1963, IBM planners perceived the beginnings of a change in this
situation. The two widely separated computer user groups were moving toward
each other in ways that were thought certain to create problems. Scientists
began to gather large files of data to be processed. This data required more
sophisticated and more efficient input and output facilities. Business applica-
tions people began to use regression analysis to build management information
systems, which required floating-point data and arrays. It began to appear that
computing installations would soon require two separate computers and techni-
cal staffs, supporting two very different programming languages.^8
These perceptions naturally led to the concept of designing a single univer-
sal computer that would be capable of doing both floating-point and decimal
arithmetic, and therefore both scientific and business applications. Thus was
born the concept of the IBM System/360 line of computers. Along with this
came the idea of a programming language that could be used for both business
and scientific applications. For good measure, features to support systems pro-
gramming and list processing were thrown in. Therefore, the new language was
to replace Fortran, COBOL, LISP, and the systems applications of assembly
language.- At the time, large computer installations required both full-time hardware and full-time sys-
tem software maintenance staff.