Showing papers in "Ibm Systems Journal in 1970"

Evaluation techniques for storage hierarchies

Abstract: The design of efficient storage hierarchies generally involves the repeated running of "typical" program address traces through a simulated storage system while various hierarchy design parameters are adjusted. This paper describes a new and efficient method of determining, in one pass of an address trace, performance measures for a large class of demand-paged, multilevel storage systems utilizing a variety of mapping schemes and replacement algorithms. The technique depends on an algorithm classification, called "stack algorithms," examples of which are "least frequently used," "least recently used," "optimal," and "random replacement" algorithms. The techniques yield the exact access frequency to each storage device, which can be used to estimate the overall performance of actual storage hierarchies.

Automatic generation of test cases

Abstract: The machine production of programs for testing certain aspects of programming products has been achieved. The system has been successfully used on a number of products to establish their reliability in accepting new test cases without error. The input to the system is a syntax definition in a formal notation. The construction of such a definition for a high-level language is an exacting task. It yields important bonuses by deepening knowledge of the structure of the language and showing up obscurities or ambiguities in the existing documentation, Definitions exist for ECMA Algol, FORTRAN IV, and a major subset of PL/I. The future effort required to adapt the definitions to particular versions of these languages should be small.

A virtual machine time-sharing system

Abstract: Time-sharing has resulted in the development of methods to increase the utilization of computers. In this paper, one such method employing the concept of the virtual machine is discussed. Described are the design objectives of CP-67/CMS, a multi-access system that manages the resources of a computer set up for time-sharing such that each user appears to have a complete, dedicated computer at his disposal. Also discussed are the system operation and some of its applications.

The authorization problem in shared files

Abstract: The problem of sharing information while protecting proprietary data in large computer files is reviewed. The author suggests certain guidelines for data protection in general-purpose, time-sharing systems, and develops a model of a secured shared file. Operation of the system based on these guidelines is discussed.

Code-generation technique for large-language compilers

Abstract: A solution is proposed to the problem of optimizing code generation by a large-language compiler. A high-level definitional language is used to define the code mappings, and an interpreter executes the routines in this language during the one-pass, text-driven code-generation phase. The technique might also be applied to extendable languages and shared-component compilers.

Compiler assignment of data items to registers

Abstract: This paper formulates as integer programmling problems three methods for assigning data items to registers in the compilation process--the one-one, many-one, and many-few global assignment methods Three algorithms are described for obtaining feasible solutions to the many-one and many-few global assignment problems One provides an optimal solution The others, which provide good approximations, appear to be sufficiently fast for inclusion in an optimizing compiler

A heuristic approach to task dispatching

Abstract: This paper describes an experimental algorithm for allocating use of a central processing unit to perform separate data processing tasks in a multitasking system. The algorithm, which may control only a subset of the tasks being performed by the system, appears to improve run time for some work loads. Tasks with a recent history of using input/output facilities are given preference. This heuristic treatment of tasks is carried over to the algorithm itself, which modifies its own characteristics based on its overall effectiveness in handling the tasks under its control.

On-line inquiry under a small-system operating system

Abstract: Operating systems for small computers are more restricted in their capabilities than those used on larger computers and are generally not designed for multiprogramming. However, some facility is needed to permit such actions as inquiries. This paper discusses an option to a small operating system that permits interruptions of a job, execution of a program to handle an inquiry, and return to the interrupted job. A description of the operating system serves as a basis in discussing the characteristics of the option.

Single-server queuing processes in computing systems

Abstract: Reviewed are applications of queuing models that may be economically useful in computing system analysis. With emphasis on terminal-oriented systems with priorities, methods are given for estimating such average quantities as service time, waiting time, and response time. Examples illustrate these methods and their ranges of efficiency, beyond which simulation techniques may be preferable.

A structure for real-time stenotype transcription

Abstract: We have experimentally demonstrated the technical feasibility of on-line Stenotype transcription for System/360 using a compacted dictionary program and a search algorithm for content addressing variable-length dictionary arguments. Methods of reducing word errors from twenty-seven percent to approximately six percent are discussed. Retraining in Stenotype extensions as well as modifications of the dictionary organization algorithm permit this reduction in the word-error rate.

A model of floating buffering

Abstract: Discussed in this paper is the effect of floating buffering on the execution time of a program. An analytic model of floating buffering is developed and discussed. It is shown that with use of the model it is possible to compute the run time of a program as a function of the number of floating buffers it uses.

Interactive aeronautical charting

Abstract: The computer-assisted aeronautical charting system replaces many tedious operations in manually up-dating aeronoautical charts. By providing interactive communication with the display, the system emphasizes the editor's (chart compiler's) real contribution—his ability to aesthetically and efficiently resolve conflicts in two-dimensional data presentations. Therefore, the concepts discussed here are potentially transferable to applications involving the two-dimensional mapping of structured data, e.g., newspaper page layout, public utility mapping, and chemical and other such processing plant design.

Interactive Saturn flight program simulator

Abstract: Space vehicle control, guidance, and navigation require onboard computers. Mission safety and success demand high program reliability without preliminary in-flight testing. Interactive Saturn flight simulation discussed in this paper tests all normal and perturbed launch vehicle interactions with the mission computer and programs to find and correct programming problems. Using a graphics console, flight analysts execute mission programs, make programming changes, and observe and document the simulated reactions of the launch vehicle.

Trajectory control programs in support of Apollo missions

Abstract: Once the trajectory of a spacecraft in flight has been predicted, control measures are required to ensure that the trajectory data is applied in a consistent manner when calculating the many trajectory-related parameters required by the flight controllers of the space flight. This paper describes the queue control techniques used in generating the predicted trajectory and the subsequent use of the trajectory data. The queue control logic that is discussed requires a minimum amount of main storage while a task is waiting to be performed.