Accession Number : ADA255656


Title :   Ada-Based Multitasking Terminal I/O


Descriptive Note : Technical rept.


Corporate Author : NAVAL SURFACE WARFARE CENTER DAHLGREN VA


Personal Author(s) : Chalkley, John C ; Masters, Michael W


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a255656.pdf


Report Date : Feb 1992


Pagination or Media Count : 119


Abstract : This report describes ANSI Terminal Services, a reusable Ada-based layered approach to providing protected asynchronous terminal I/O in a multitasking environment. The traditional single-threaded, sequential programming model is inadequate for Ada multitask programs, particularly for real-time applications. An application is likely to contain several tasks needing to perform output concurrently. Any shared resources contained in the I/O software must, therefore, be protected through some form of mutual exclusion. Also, an application will likely need to support input operations concurrently with outputs. This requirement is especially important since Ada implementations on most current operating systems are process synchronous, rather than task synchronous/process asynchronous. As a result, they cause the entire user process to block on an input request. Thus, other program tasks that may be performing critical functions are suspended until user input is complete. Such a result is clearly inappropriate in a real-time environment. ANSI Terminal Services solves these problems and provides both a standard programmer interface and the necessary multitasking concurrency control.


Descriptors :   *ADA PROGRAMMING LANGUAGE , *REUSABLE EQUIPMENT , *ASYNCHRONOUS COMPUTERS , *DATA PROCESSING TERMINALS , INPUT , OUTPUT , CONTROL , FUNCTIONS , REQUIREMENTS , ENVIRONMENTS , MODELS , APPROACH , TERMINALS , REAL TIME , INTERFACES , COMPUTER PROGRAMMING , OPERATION , STANDARDS , RESOURCES , PROGRAMMERS


Subject Categories : Computer Programming and Software
      Computer Hardware


Distribution Statement : APPROVED FOR PUBLIC RELEASE