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The constructs of a simple programming language are introduced and described informally in terms of values and side-effects. A translator is defined which translates the language into flowcharts for a simple machine. The action of the machine in executing a flowchart is defined. A proof is constructed that the effect of translating and executing any program can be expressed solely in terms of the value and side-effect of the program. During the course of constructing the proof, formal definitions of the concepts of value and side-effect are derived in order to make the proof rigorous. Correctness of the implementation involves checking that the definitions derived in the step above are an acceptable formalization of the informal description given in the first step. [ABSTRACT FROM AUTHOR]

A new datatype, called a block, has been implemented for SNOBOL4. A block is a three-dimensional aggregate of characters in the form of a right parallelepiped, best thought of as a three-dimensional extension to a string. (The third dimension is used for overstriking.) Blocks may he printed, concatenated in any of three dimensions, and merged on the basis of program-defined connection points. Some blocks adapt In size and shape to their environment. Blocks and their operations are mainly used for composing printable output. A variety of graphical problems (including flowcharting, bargraphs, logic diagrams, mathematical-equation formation, and text justification and preparation) have been programmed on a printer in what appears to be an easy and natural way. In addition to these somewhat specialized applications, blocks appear to be a good general purpose device-independent output formation mechanism especially suitable for nonnumerical work. The concept of a block is largely language independent. That is, blocks require little in the way of specialized syntax and could readily be absorbed into the external structure of most programming languages. [ABSTRACT FROM AUTHOR]

A method of incremental compilation is presented which applies especially to programming languages in which statements can be nested (such as Algol and PL/I) The method permits editing of the source language using a general purpose text editor, and incremental processing of changes without frequent recompilation of entire routines. The essential points of the method are: (1) the syntax of the language is restricted insofar as which constructs may occur on lines; (2) an internal data structure (called the skeleton) is maintained to represent the statement structure; (3) the recompilation is partially batched in the sense that recompilation of modified lines does not occur until the last of a set of editing commands has been received; and (4) the parsing and compilation are factored into two parts, that done on individual lines and that done globally to handle the relationships between the lines. [ABSTRACT FROM AUTHOR]

The paper describes a scheme for symbolic manipulation of index expressions which arise as a by-product of the symbolic manipulation of expressions in the matrix calculi described by the authors in a previous paper. This scheme attempts program optimization by transforming the original algorithm rather than the machine code. The goal is to automatically generate code for handling the tedious address calculations necessitated by complicated data structures. The paper is therefore preoccupied with "indexing by position." The relationship of "indexing by name" and "indexing by position" is discussed. [ABSTRACT FROM AUTHOR]

The classical process of partitioning an array into subarrays is extended to a more useful array language operation. Various modes of partitioning are defined for different types of arrays, so that subarrays may vary over the original array in a nearly arbitrary manner. These definitions are motivated with several realistic examples to illustrate the value of partitioning for array languages. Of general interest Is the data structure for partitioning. This consists of dynamic tree structures which are used to derive and maintain the array control information. These are described in sufficient detail to be of value In the design of other array languages. The description presented in this paper is Implemented in a new array language, OL/2, currently under development at the University of lllinois. [ABSTRACT FROM AUTHOR]

A language, BLISS, is described. This language is designed so as to be especially suitable for use in writing production software systems for a specific machine (the PDP-10): compilers, operating systems, etc. Prime design goals of the design are the ability to produce highly efficient object code, to allow access to all relevant hardware features of the host machine, and to provide a rational means by which to cope with the evolutionary nature of systems programs. A major feature which contributes to the realization of these goals is a mechanism permitting the definition of the representation of all data structures in terms of the access algorithm for elements of the structure. [ABSTRACT FROM AUTHOR]