WINDOWS编程中的“句柄”类型

句柄(HANDLES)是整个WINDOWS编程的基础,因此,必须准确地理解句柄指的是什么。许多WINDOWS编程指南中都是把句柄定义为“WIN-DOWS使用的一个唯一的整数值,是用来标识应用程序中的一个对象,诸如一个窗口、一个实例、一个菜单、一个存储器、一个输出设备、一个控制、或者一个文件等等。”这在模块定义文件中可清楚地看到这一点。不过,在编程中,我们却发现WINDOWS应用程序往往只能存取句柄,而不能存取句柄所代表的实际数据。这些都使WINDOWS编程者感到高深莫测。 总之,许多人把句柄理解为一个被传送物,也就是说,如果一个函数返回了一个模块句柄,而另一个函数需要一个模块句柄的话,这时,你的程序就象一个管道,将句柄从一个函数传送到另一个函数,而无须知道这个句柄是什么。     

不用就隐藏双系统运行更安全

现在有不少人都安装了双操作系统。若登录其中任意一个系统,另外一个系统所在的分区也是可见的,若是病毒破坏了其中一个系统,那么另外一个系统的分区同样会被感染,同时,假如在一个系统中误删除了另外一个系统中的必备文件,也可能导致另外一个系统不能启动。如果登录一个系统后,另一个系统所在的分区能够自动隐藏,则可完美地解决这一问题。接下来,笔者就以Win XP／Windows7双系统为例,给大家介绍一下如何来实现。     

主程序

主程序是一个不以FUNCTION或SUBROUTINE语句作为第一个语句的程序单位, 它可以以一个PROGRAM语句作为它的第一个语句。在一个可执行的程序中必须要有一个主程序。一个可执行程序的执行是从执行主程序的第一个可执行语句开始的。 14.1 pROGRAM语句     

问与答

26.问:任务、进程和线程有何不同? 答:三个词中,任务(task)是最抽象的,是一个一般性的术语,指由软件完成的一个活动。一个任务既可以是一个进程,也可以是一个线程。简而言之,它指的是一系列共同达到某一目的的操作。例如,读取数据并将数据放入内存中。这个任务可以作为一个进程来实现,也可以作为一个线程(或作为一个中断任务)来实现。     

小然杂记

不知道为什么,总是喜欢一个人发呆、一个人逛街、一个人胡思乱想、一个人自言自语、一个人……尽管身边挚友不乏,但一个人独处的感觉却是难以言喻的奇妙。     

World-Wide Web有何用?

过去我们常常有一个部门叫做Interchange。它是一个联机服务和一个出版平台。它有一个复杂的用户界面,无论用于检索还是浏览都是一个优秀的环境,而且它能提供相当丰富的图形。而我曾见到过的第一个Web浏览     

QBASIC中子程序的应用

结构化程序设计的基本方法是“自顶向下,逐步求精”,其实就是将一个大的程序分成若干个模块,每个模块完成一个或几个功能,并给它定义一个惟一的名字,以便调用,这就是所谓的模块化。这样,一个程序就包含一个主模块和若干子模块。由于模块是通过执行一组语句来完成一个特定的操作过程,所以模块又称为“过程”。“执行一个过程”的意思就是调用一个子程序或函数模块。用一个简单的例子来说明“模块化”的概念。假设有一个“学生数据处理”程序,由3部分组成,即分为3个模块,学生基本情况,学生奖惩情况和输出报表。每个模块可以用一个子程序来实现其功能。这样一个相对较大的、较复杂的任务就分解为3个较简单     

利用XML视图更新关系数据库

XML已成为数据交换的一个重要介质,也被作为一个接口,即一个关系数据库的一个视图。此前,关于利用XML视图查询关系数据库(例如Silkroute)的问题有人已经做过深入探讨。对于关系数据库上XML视图的可更新性,首先考虑的是如何通过一个XML视图更新一个关系数据库的问题,把嵌套的关系代数作为一个关系数据库的XML视图,然后再考虑这个视图什么时候是可更新的问题。     

.NET下一代互联网新构想

从实质上来看,.NET代表了一个集合、一个环境、一个可以作为平台支持下一代互联网的可编程结构。因此,它既是一个用户体验,也是一个开发商体验的集合。但是在作为服务的软件世界中,很难说.NET具体是什么,也很难把.NET放在一个盒子中……     

主程序

主程序是一个不以FUNCTION、SUBROUTINE或BLOCK DATA语句作为第一个语句的程序单位。它可以以一个PROGRAM语句作为它的第一个语句。在一个可执行的程序中必须要有一个主程序,一个可执行程序的执行是从执行主程序的第一个可执行语句开始的。 14.1 PROGRAM语句     

动态扰动解耦补偿器

本文利用极大绝对能观子系统及其对偶概念,对扰动解耦问题有解的充要条件给出了一个新的形式。对一类多输入多输出系统,给出了解耦补偿器的一般形式和稳定解耦的充要条件。     

Characterizations and effective computation of supremal relatively observable sublanguages

Recently we proposed relative observability for supervisory control of discrete-event systems under partial observation. Relative observability is closed under set unions and hence there exists the supremal relatively observable sublanguage of a given language. In this paper we present a new characterization of relative observability, based on which an operator on languages is proposed whose largest fixpoint is the supremal relatively observable sublanguage. Iteratively applying this operator yields a monotone sequence of languages; exploiting the linguistic concept of support based on Nerode equivalence, we prove for regular languages that the sequence converges finitely to the supremal relatively observable sublanguage, and the operator is effectively computable. Moreover, for the purpose of control, we propose a second operator that in the regular case computes the supremal relatively observable and controllable sublanguage.     

计算DES监控中优于闭可识别语言的闭可观子语言

本文给出一种求闭能观子语言的算法，该算法经ｍ步（系统中离散事件个数）收敛；并且证明无论对系统中事件如何排序，由该算法求出的闭能观子语言总包含最大闭可识别子语言。     

Modular Control of Discrete-Event Systems With Coalgebra

Modular supervisory control of discrete-event systems, where the overall system is a synchronous (parallel) product of subsystems, is considered. The main results of this paper are formulations of sufficient conditions for the compatibility between the synchronous product and various operations stemming from supervisory control as supervised product and supremal controllable sublanguages. These results are generalized to the case of modules with partial observations: e.g., modular computation of supremal normal sublanguages is studied. Coalgebraic techniques based on the coinduction proof principle are used in our main results. Sufficient conditions are derived for modular to equal global control synthesis. An algorithmic procedure for checking the new conditions is proposed and the computational benefit of the modular approach is discussed and illustrated by comparing the time complexity of modular and monolithic computation.     

Formulas for a class of controllable and observable sublanguages larger than the supremal controllable and normal sublanguage

In this paper, we give some new methods for synthesis of controllers of discrete event dynamical systems (DEDS) with partial event informations. Given a regular target language L, we construct some effective computable algorithms for computing the controllable and observable sublanguages of L. We show that any one of these controllable and observable sublanguages obtained by our algorithms is larger than the supremal controllable and normal sublanguage of L.     

非阻塞监控器设计中的语言优化方法

本文研究在设计非阻塞监控器时所涉及到的语言的优化方法，首先给出了Ｌｍ（Ｇ）闭语言的计算公式，然后提出了能控Ｌｍ（Ｇ）闭子语言的逐级优化途径，对于目前获得的部分优化语言的封闭解进行了总结，并对各语言类之间的关系进行了分析。     

线性控制系统规范结构的新解释与它的算法

应用绝对能观性的概念可以对线性控制系统的规范结构赋于新的解释。文中指出,规范结构由四部分组成,即绝对能观但不能控;绝对能控但不能观;绝对能观与能控;绝对不能观不能控。应用我们引入的方法,规范结构可以用矩阵的初等变换来实现。     

An introduction to hierarchical systems theory

Hierarchical theory is a new and promising area of general systems theory. This theory deals basically with the decomposition of a system into subsystems forming a hierarchical structure and is, therefore, on method of dealing with complexity. These subsystems or infimals are coordinated by a coordinator or supremal in such a way as to obtain original system objectives. Hence, hierarchical theory is applicable to systems with a natural hierarchical structure or whose dimensionality is so high as to present computational difficulties. Thus it would appear to be particularly appropriate for use in public and societal systems problems.This paper presents a tutorial introduction to hierarchical system theory. Optimization theory is used as a vehicle for presenting the hierarchical concepts, although estimation, identification and other systems problems are also amenable to hierarchical structuring. An example is solved to demonstrate the theory and some computational considerations.     

设计Robust控制器的一个新准则和新算法

本文讨论具有最优输出调节品质的Robust控制器,利用绝对能观子系统的概念研究干扰 对闭环系统输出的影响.在一定条件下,从原系统中可分离出一个绝对能观子系统,这样使 输出调节的最优化计算得到简化. 本文给出了完成上述任务的一个算法.     

Observability and decentralized control of fuzzy discrete-event systems

Fuzzy discrete-event systems as a generalization of (crisp) discrete-event systems have been introduced in order that it is possible to effectively represent uncertainty, imprecision, and vagueness arising from the dynamic of systems. A fuzzy discrete-event system has been modeled by a fuzzy automaton; its behavior is described in terms of the fuzzy language generated by the automaton. In this paper, we are concerned with the supervisory control problem for fuzzy discrete-event systems with partial observation. Observability, normality, and co-observability of crisp languages are extended to fuzzy languages. It is shown that the observability, together with controllability, of the desired fuzzy language is a necessary and sufficient condition for the existence of a partially observable fuzzy supervisor. When a decentralized solution is desired, it is proved that there exist local fuzzy supervisors if and only if the fuzzy language to be synthesized is controllable and co-observable. Moreover, the infimal controllable and observable fuzzy superlanguage, and the supremal controllable and normal fuzzy sublanguage are also discussed. Simple examples are provided to illustrate the theoretical development.