Abstract The UNIX UNIX is a trademark of Bell Laboratories. operating system provides an especially congenial programming environment, in which it is not only possible, but actually natural, to write programs quickly and well. Several characteristics of the UNIX system contribute to this desirable state of affairs. Files have no type or internal structure, so data produced by one program can be used by another without impediment. The basic system interface for input and output provides homogeneous treatment of files, I/O devices and programs, so programs need not care where their data comes from or goes to. The command interpreter makes it convenient to connect programs, by arranging for all data communication. Complex procedures are created not by writing large programs from scratch, but by interconnecting relatively small components. These programs are small and concentrate on single functions, and therefore are easy to build, understand, describe, and maintain. They form a high level toolkit whose existence causes programmers to view their work as the use and creation of tools, a viewpoint that encourages growth in place of reinvention. Tools interact in a limited number of ways, but can be used in many different combinations. Thus, an addition to the toolkit tends to improve the programming power of the user faster than it increases the complexity of interconnection and maintenance. Finally, tools are connected at a very high level by a powerful command language interpreter. The error‐prone and expensive process of program writing can often be avoided in favor of program‐using. In this paper we will present a variety of examples to illustrate this methodology, focusing on those aspects of the system and supporting software which make it possible.

ASSIST is a high-speed assembler/interpreter system for IBM System/360 and related computers. It is designed primarily for efficient processing of student jobs, and offers a number of educational features. ASSIST is now being used at a number of installations under widely varying circumstances. This paper analyzes the design process and decisions leading to ASSIST, concentrating on the factors felt to be most important to its usage. Implementation problems and experiences are noted, and conclusions drawn from them regarding the design of student job processors and desired operating system facilities to support them.