it-e-03 Computer hardware

Computer hardware has four parts: the central processing unit (CPU) and memory, storage
hardware, input hardware, and output hardware.
The part of the computer that runs the program is known as the processor or central processing
unit (CPU). In a microcomputer, the CPU is on a single electronic component, the microprocessor
chip, within the system unit or system cabinet. The CPU itself has two parts: the control unit and
the arithmetic-logic unit. In a microcomputer, these are both on the microcomputer chip.
The Control Unit The control unit tells the rest of the computer system how to carry out a
program's instructions. It directs the movement of electronic signals between memory and the
arithmetic-logic unit. It also directs these control signals between the CPU and input and output
The Arithmetic-Logic Unit The arithmetic-logic unit, usually called the ALU, performs
two types of operations—arithmetic and logical. Arithmetic operations are, as you might expect,
the fundamental math operations: addition, subtraction, multiplication, and division. Logical
operations consist of comparisons. That is , two pieces of data are compared to see whether one is
equal to, less than, or greater than the other.
Memory Memory is also known as primary storage, internal storage, it temporarily holds
data, program instructions, and information. One of the most important facts to know about
memory is that part of its content is held only temporarily. In other words, it is stored only as
long as the computer is turned on. When you turn the machine off, the content immediately
vanish. The stored contents in memory are volatile and can vanish very quickly.
Storage Hardware [1]The purpose of storage hardware is to provide a means of storing
computer instructions and data in a form that is relatively permanent, that is, the data is not lost
when the power is turned off—and easy to retrieve when needed for processing.There are four
kinds of storage hardware: floppy disks, hard disks,optical disk,andmagnetic tape.
Floppy Disks Floppy disks are also called diskettes, flexible disks, floppies, or simply

disks. The plastic disk inside the diskette cover is flexible, not rigid. They are flat, circular pieces
of mylar plastic that rotate within a jacket. Data and programs are stored as electromagnetic
charges on a metal oxide film coating the mylar plastic.
Hard Disks Hard disks consist of metallic rather than plastic platters. They are tightly
sealed to prevent any foreign matter from getting inside. Hard disks are extremely sensitive
instruments. The read-write head rides on a cushion of air about 0.000001 inch thick. It is so thin
that a smoke particle, fingerprint, dust, or human hair could cause what is known as a head crash.
A head crash happens when the surface of the read-write head or particles on its surface contact
the magnetic disk surface. A head crash is a disaster for a hard disk. It means that some or all of
the data on the disk is destroyed. Hard disks are assembled under sterile conditions and sealed
from impurities within their permanent containers.
Optical Disks Optical disks are used for storing great quantities of data. An optical disk can
hold 650 megabytes of data—the equivalent of hundreds of floppy disks. Moreover, an optical disk
makes an immense amount of information available on a microcomputer. In optical-disk technology,
a laser beamalters the surface of a plastic or metallic disk to represent data. To read the data, a laser
scans these areas and sends the data to a computer chip for conversion.
Magnetic Tape Magnetic tape is an effective way of making a backup, or duplicate, copy of
your programs and data. We mentioned the alarming consequences that can happen if a hard disk
suffers a head crash. You will lose some or all of your data or programs. Of course, you can always
make copies of your hard-disk files on floppy disks. However, this can be time-consuming and may
require many floppy disks. Magnetic tape is sequential access storage and can solve the problem
mentioned above.
Input Hardware Input devices take data and programs people can read or understand and
convert them to a form the computer can process. This is the machine-readable electronic signals
of 0s and 1s. Input hardware is of two kinds: keyboard entry and direct entry.
Keyboard Entry Data is input to the computer through a keyboard that looks like a
typewriter keyboard but has additional keys. In this method, the user typically reads from an
original document called the source document. The user enters that document by typing on the
Direct Entry :Data is made into machine-readable form as it is entered into the computer,
no keyboard is used. Direct entry devices may be categorized into three areas: pointing devices
(for example, mouse, touch screen, light pen, digitizer are all pointing devices), scanning devices
(for example, image scanner, fax machine, bar-code reader are all scanning devices), and
voice-input devices.
Output Hardware Output devices convert machine-readable information into people-readable
form. Common output devices are monitors, printers, plotters, and voice output.
Monitors Monitors are also called display screen or video display terminals. Most monitors that
sit on desks are built in the same way as television sets, these are called cathode-ray tubes. Another type
of monitor is flat-panel display, including liquid-crystal display (LCD), electroluminescent (EL) display

and gas-plasma display. An LCD does not emit light of its own. Rather, it consists of crystal molecules.
[2]An electric field causes the molecules to line up in a way that alters their optical properties.
Unfortunately, many LCDs are difficult to read in sunlight or other strong light. A gas-plasma display is
the best type of flat screen. Like a neon light bulb, the plasma display uses a gas that emits light in the
presence of an electric current.
Printers There are four popular kinds of printers: dot-matrix, laser, ink-jet, and thermal.
Dot-Matrix Printer Dot-matrix printers can produce a page of text in less than 10 seconds
and are highly reliable. They form characters or images using a series of small pins on a print
head. The pins strike an inked ribbon and create an image on paper. Printers are available with
print heads of 9, 18, or 24 pins. One disadvantage of this type of printer is noise.
Laser Printer The laser printer creates dotlike images on a drum, using a laser beam light
source. [3]The characters are treated with a magnetically charged inklike toner and then are
transferred from drum to paper. A heat process is used to make the characters adhere. The laser
printer produces images with excellent letter and graphics quality.
Ink-Jet Printer An ink-jet printer sprays small droplets of ink at high speed onto the
surface of the paper. This process not only produces a letter-quality image but also permits
printing to be done in a variety of colors.
Thermal Printer A thermal printer uses heat elements to produce images on heat-sensitive
paper. Color thermal printers are not as popular because of their cost and the requirement of
specifically treated paper. They are a more special use printer that produces near photographic
output. They are widely used in professional art and design work where very high quality color is
Plotters Plotters are special-purpose output devices for producing bar charts, maps, architectural
drawings, and even three-dimensional illustrations. Plotters can produce high-quality multicolor
documents and also documents that are larger in size than most printers can handle. There are four types
of plotters: pen, ink-jet, electrostatic, and direct imaging.
Voice-Output Devices Voice-output devices make sounds that resemble human speech but
actually are pre-recorded vocalized sounds. Voice output is used as a reinforcement tool for
learning, such as to help students study a foreign language. It is used in many supermarkets at the
checkout counter to confirm purchases. Of course, one of the most powerful capabilities is to
assist the physically challenged.

Continue reading it-e-03 Computer hardware

skype4java :

skype4java 地址:

使用jni封装skype com+接口


Win32Connector::protected void initializeImpl() 方法有些问题,其意图是如果没又找到skype库就从包里面解压缩skype.dll到临时文件夹下,但是我不知道为什么作者要用zip遍历,而不是使用类加载器获得资源来解压缩。


try {
        } catch(Throwable e) {
            try {
                if(!ConnectorUtils.checkLibraryInPath(LIBFILENAME)) {
                    String dllPath;
                    String tmpDir = System.getProperty("");
                    if(!tmpDir.endsWith("" + File.separatorChar)) {
                        tmpDir = tmpDir + File.separatorChar;
                    dllPath = tmpDir + LIBFILENAME;
                    File dll = new File(dllPath);
                    if(!dll.exists()) {
                        if(!dll.exists()) {
                            throw new RuntimeException("can't load " + dllPath);
            } catch(Exception e1) {
                throw new RuntimeException(e1);

private void extractDll(File destFile) {
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
        InputStream input = loader.getResourceAsStream(LIBFILENAME);
        FileOutputStream output = null;
        try {
            output = new FileOutputStream(destFile);
            byte[] buffer = new byte[1024 * 4];
            long count = 0;
            int n = 0;
            while(-1 != (n = {
                output.write(buffer, 0, n);
                count += n;
        } catch(Exception e) {
            throw new RuntimeException(e);
        } finally {
            try {
                if(null != input) {
            } catch(IOException e) {
            try {
                if(null != output) {
            } catch(IOException e) {


winp.jar 检查是否running

swt.jar 借用OS基础功能

Continue reading skype4java :



出于成本和便捷因素的考虑,目前很多公司和消费者都已经开始使用VoIP的电话服务。根据SearchVoIP网站在2007年6月份进行的一项调查,纯IP PBX系统在2007年第一季度的销售比上一季度上涨了76%。







然而Internet上的主机数量不断稳定增长,最终我们必然需要扩展更大的地址空间。除了巨大的地址容量之外,IPv6还通过IPsec这一基础的协议组件提供更好的安全性能。目前像Windows Vista、Windows Server 2008、Mac OS X 10.3以及其他最新的操作系统都已经默认支持IPv6,这些操作系统的支持可以看作IPv6已经具备了腾飞的基础。



虚拟化已经出现一段时间了,但目前它才真正开始成熟。微软即将推出的Windows Server 2008服务器操作系统将会包含其大力研发的Windows hypervisor技术(Viridian);而VMWare也提供了免费的VMWare Server,红帽和SuSE也计划在下一版本的服务器产品中包含Xen hypervisor技术。我们可以判定,虚拟机的概念将会在未来几年上升到一个全新的阶段。



代表了下一代以太网的Web 2.0采用了SaaS(Software as a Service)模式,它通过互联网提供软件服务,而不需要在每个用户的电脑里单独安装应用程序。一些IT专家已经警告称SaaS将会完全取代企业内IT 管理员的工作,但更广为接受的说法则称SaaS将会把IT管理员从繁重的配置和维护工作中解脱出来,而将精力更加集中地投入到对全局的计划以及融合上。







学习与VPN技术相关的不同的技能十分重要,比如SSL VPN技术就十分有用。我们可以利用健康监测以及隔离远程客户端阻止那些未达到安全要求最低准则的电脑接入局域网,以免其对网络产生危害。



未来一定会出现更快速也更安全的无线技术。你需要了解802.11n,这一新的标准目前还处于开发阶段,但已经确定会在2008年底正式公布。 802.11n能够提供典型的74Mbps吞吐量,最高可达248Mbps,另外它的有效半径也远高于目前的802.11a/b/g标准,可以达到70 米。



然而出于应用软件的原因或者个人喜好,其他用户将会继续使用Windows,另外还有很多用户在混合着使用苹果电脑,尤其是在图形处理领域。 仅仅精通一种平台在今后是不会成为IT专家的;你需要周游于不同的操作系统之间,解决各种问题。

随着VoIP越来越流行,统一通信的概念——不同通信技术的汇合,诸如电子邮件、语音消息、文本短信以及传真等的汇合—— 将会成为下一波技术浪潮的热点。用户今后可以从一个单独的界面上接入所有的通信设备,比如从各种不同的设备上接入电子邮箱,这些设备可以是台式电脑、笔记本电脑、智能手机或者PDA、甚至传统电话。




802.11b 2.4g频段 最大11m/s 一般6.5m/s。

Continue reading [转]未来五年可能流行的十大网络技术

it-e-04 information appliance

An "information appliance (IA)" is any device that can process information, signals,
graphics, animation, video and audio; and can exchange such information with another IA device.
Typical devices could be smartphones, smartcard, PDAs, and so on. Digital cameras, ordinary
cellular phones, set-top boxes, and LCD TVs are not information appliances unless they become
capable of communications and information functions. Information appliances may overlap in
definition or are sometimes referred to as smart devices, mobile devices, wireless devices,
internet appliances, web appliances, handhelds, handheld devices or smart handheld devices.
Early Appliances For a short while during the middle and late 1980s there were a few
models of simple electronic typewriters fitted with screens and some form of memory storage.
These devices had some of the attributes of an information appliance. One of these dedicated
word processor machines, the Canon Cat was actually designed by Jef Raskin as the forerunner
of the idea of the information appliance.
Information appliances tend to be consumer devices that perform only a few targeted tasks
and are controlled by a simple touchscreen interface or push buttons on the device's enclosure.
Open Standard Protocols In an ideal world, any true information appliance would be able to communicate with any other information appliance using open standard protocols and
technologies, regardless of the maker of the software or the hardware. The communications
aspects and all user interface elements would be designed together so that a user could switch
seamlessly from one information appliance to another.

Continue reading it-e-04 information appliance

myeclipse maven web项目建立

开始建立一个gernaeral project,





项目上右键添加web属性,并指定webv root文件夹和context








关于pom中对war plugin的配置此处不叙.



    <attribute name="webrootdir" value="/src/main/webapp" />

Continue reading myeclipse maven web项目建立

读书笔记:Effective Java, Second Edition-1,10章


一 对象构造销毁

Item 1用静态方法代替构造器









Item 2当构造一个对象需要很多的参数时,建议使用builder方式


NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).calories(100).sodium(35).carbohydrate(27).build();


Item 3强制单例类的构造器为不可见,或者使用enum来做单例。

Item 4像Utils这样的类也将他的构造器设为不可见,你懂的。

Item 5不要创建不必要的对象


Item 6内存泄露

public Object pop() {
if (size == 0)
throw new EmptyStackException();
return elements[--size]; //这里应该Object result = elements[--size];elements[size] = null;



Item 7: 避免析构

二 对象通用方法

十 并发

Item 66: 同步访问多线程可修改数据



// Broken! - How long would you expect this program to run?
public class StopThread {
private static boolean stopRequested;
public static void main(String[] args)
throws InterruptedException {
Thread backgroundThread = new Thread(new Runnable() {
public void run() {
int i = 0;
while (!stopRequested) //编译器会优化为while (true),因为stopRequested没有同步
stopRequested = true;

Item 67: Avoid excessive synchronization






In a multicore world, the real cost of excessive synchronization is not the CPU time spent obtaining locks; it is the lost opportunities for parallelism and the delays imposed by the need to ensure that every core has a consistent view of memory

Item 68: Prefer executors and tasks to threads

1.5开始包含的Executor Framework,queue和异步

创建ExecutorService executor = Executors.newSingleThreadExecutor();



它试图终止线程的方法是通过调用Thread.interrupt()方法来实现的,但是大家知道,这种方法的作用有限,如果线程中没有sleep 、wait、Condition、定时锁等应用, interrupt()方法是无法中断当前的线程的。所以,ShutdownNow()并不代表线程池就一定立即就能退出,它可能必须要等待所有正在执行的任务都执行完成了才能退出。




Item 69: Prefer concurrency utilities to wait and notify


Executor Framework,

concurrent collections; 并发性能比普通高






package com.eyesmore.concurrent;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CountDownLatchDemo {
    private static final int PLAY_AMOUNT = 10;
    public static void main(String[] args) {
         * 比赛开始:只要裁判说开始,那么所有跑步选手就可以开始跑了
         * */
        CountDownLatch begin = new CountDownLatch(1);
         * 每个队员跑到末尾时,则报告一个到达,所有人员都到达时,则比赛结束
         * */
        CountDownLatch end = new CountDownLatch(PLAY_AMOUNT);
        Player[] plays = new Player[PLAY_AMOUNT];
        for(int i = 0;i<PLAY_AMOUNT;i++) {
            plays[i] = new Player(i+1,begin,end);
        ExecutorService exe = Executors.newFixedThreadPool(PLAY_AMOUNT);
        for(Player p : plays) {//各就各位
        try {
        } catch (InterruptedException e) {
        } finally {
class Player implements Runnable {
    private int id;
    private CountDownLatch begin;
    private CountDownLatch end;
    public Player(int id, CountDownLatch begin, CountDownLatch end) {
        super(); = id;
        this.begin = begin;
        this.end = end;
    public void run() {
        try {
            System.out.println("Play "+id+" has arrived. ");
        } catch (InterruptedException e) {
        } finally {



package examples.ch06.example01;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TestCyclicBarrier {
    // 徒步需要的时间: Shenzhen, Guangzhou, Shaoguan, Changsha, Wuhan
    private static int[] timeWalk = { 5, 8, 15, 15, 10 };
    // 自驾游
    private static int[] timeSelf = { 1, 3, 4, 4, 5 };
    // 旅游大巴
    private static int[] timeBus = { 2, 4, 6, 6, 7 };
    static String now() {
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        return sdf.format(new Date()) + ": ";
    static class Tour implements Runnable {
        private int[] times;
        private CyclicBarrier barrier;
        private String tourName;
        public Tour(CyclicBarrier barrier, String tourName, int[] times) {
            this.times = times;
            this.tourName = tourName;
            this.barrier = barrier;
        public void run() {
            try {
                Thread.sleep(times[0] * 1000);
                System.out.println(now() + tourName + " Reached Shenzhen");
                Thread.sleep(times[1] * 1000);
                System.out.println(now() + tourName + " Reached Guangzhou");
                Thread.sleep(times[2] * 1000);
                System.out.println(now() + tourName + " Reached Shaoguan");
                Thread.sleep(times[3] * 1000);
                System.out.println(now() + tourName + " Reached Changsha");
                Thread.sleep(times[4] * 1000);
                System.out.println(now() + tourName + " Reached Wuhan");
            } catch (InterruptedException e) {
            } catch (BrokenBarrierException e) {
    public static void main(String[] args) {
        // 三个旅行团
        CyclicBarrier barrier = new CyclicBarrier(3);
        ExecutorService exec = Executors.newFixedThreadPool(3);
        exec.submit(new Tour(barrier, "WalkTour", timeWalk));
        exec.submit(new Tour(barrier, "SelfTour", timeSelf));
        exec.submit(new Tour(barrier, "BusTour", timeBus));

Semaphore 信号量,就是一个允许实现设置好的令牌。也许有1个,也许有10个或更多。


1 是如何保证入库时,如果仓库满就等待,

2 出库时,如果仓库无货就等待的。

3 以及对仓库只有10个库位的处理。

4 对同步问题的处理。

import java.util.concurrent.Semaphore;
* 老紫竹JAVA提高教程-信号量(Semaphore)的使用。<br>
* 生产者和消费者的例子,库存的管理。
* @author 老紫竹(,
public class TestSemaphore {
  public static void main(String[] args) {
    // 启动线程
    for (int i = 0; i <= 3; i++) {
      // 生产者
      new Thread(new Producer()).start();
      // 消费者
      new Thread(new Consumer()).start();
  // 仓库
  static Warehouse buffer = new Warehouse();
  // 生产者,负责增加
  static class Producer implements Runnable {
    static int num = 1;
    public void run() {
      int n = num++;
      while (true) {
        try {
          System.out.println(">" + n);
          // 速度较快。休息10毫秒
        } catch (InterruptedException e) {
  // 消费者,负责减少
  static class Consumer implements Runnable {
    public void run() {
      while (true) {
        try {
          System.out.println("<" + buffer.take());
          // 速度较慢,休息1000毫秒
        } catch (InterruptedException e) {
   * 仓库
   * @author 老紫竹(
  static class Warehouse {
    // 非满锁
    final Semaphore notFull = new Semaphore(10);
    // 非空锁
    final Semaphore notEmpty = new Semaphore(0);
    // 核心锁
    final Semaphore mutex = new Semaphore(1);
    // 库存容量
    final Object[] items = new Object[10];
    int putptr, takeptr, count;
     * 把商品放入仓库.<br>
     * @param x
     * @throws InterruptedException
    public void put(Object x) throws InterruptedException {
      // 保证非满
      // 保证不冲突
      try {
        // 增加库存
        items[putptr] = x;
        if (++putptr == items.length)
          putptr = 0;
      } finally {
        // 退出核心区
        // 增加非空信号量,允许获取商品
     * 从仓库获取商品
     * @return
     * @throws InterruptedException
    public Object take() throws InterruptedException {
      // 保证非空
      // 核心区
      try {
        // 减少库存
        Object x = items[takeptr];
        if (++takeptr == items.length)
          takeptr = 0;
        return x;
      } finally {
        // 退出核心区
        // 增加非满的信号量,允许加入商品



synchronized (obj) { while (<condition does not hold>) obj.wait(); ... // Perform action appropriate to condition }//这是java doc里面的的范例。


Always use the wait loop idiom to invoke the wait method; never invoke it outside of a loop. The loop serves to test the condition before and after waiting. Testing the condition before waiting and skipping the wait if the condition already holds are necessary to ensure liveness. If the condition already holds and the notify (or notifyAll) method has already been invoked before a thread waits, there is no guarantee that the thread will ever wake from the wait. Testing the condition after waiting and waiting again if the condition does not
hold are necessary to ensure safety. If the thread proceeds with the action when the condition does not hold, it can destroy the invariant guarded by the lock. There are several reasons a thread might wake up when the condition does not hold:

• Another thread could have obtained the lock and changed the guarded state between
the time a thread invoked notify and the time the waiting thread woke.
• Another thread could have invoked notify accidentally or maliciously when
the condition did not hold. Classes expose themselves to this sort of mischief
by waiting on publicly accessible objects. Any wait contained in a synchronized
method of a publicly accessible object is susceptible to this problem.
• The notifying thread could be overly “generous” in waking waiting threads.
For example, the notifying thread might invoke notifyAll even if only some
of the waiting threads have their condition satisfied.
• The waiting thread could (rarely) wake up in the absence of a notify. This is
known as a spurious wakeup [Posix,; JavaSE6].



计时用 System.nanoTime()

Item 70: Document thread safety 为你的同步的方法写好文档、注释

Item 71: Use lazy initialization judiciously 主要讨论了同步情况下的懒加载问题,一般还是建议不需要迟初始化,以免造成并发情况下多次初始化的问题。

Item 72: Don’t depend on the thread scheduler


Item 73: Avoid thread groups 请用前面提到的线程池而不要使用线程组,线程组你可以忘记他们了,他们是不成功的实现。

Continue reading 读书笔记:Effective Java, Second Edition-1,10章


类加载器与 Web 容器

对于运行在 Java EE™ 容器中的 Web 应用来说,类加载器的实现方式与一般的Java 应用有所不同[默认的是从父到子]。不同的 Web 容器的实现方式也会有所不同。以 Apache Tomcat 来说,每个 Web 应用都有一个对应的类加载器实例。该类加载器也使用代理模式,所不同的是它是首先尝试去加载某个类,如果找不到再代理给父类加载器。这与一般类加载器的顺序是相反的。这是 Java Servlet 规范中的推荐做法,其目的是使得 Web 应用自己的类的优先级高于 Web 容器提供的类。这种代理模式的一个例外是:Java 核心库的类是不在查找范围之内的。这也是为了保证 Java 核心库的类型安全。

绝大多数情况下,Web 应用的开发人员不需要考虑与类加载器相关的细节。下面给出几条简单的原则:

每个 Web 应用自己的 Java 类文件和使用的库的 jar 包,分别放在 WEB-INF/classes 和 WEB-INF/lib 目录下面。多个应用共享的 Java 类文件和 jar 包,分别放在 Web 容器指定的由所有 Web 应用共享的目录下面。当出现找不到类的错误时,检查当前类的类加载器和当前线程的上下文类加载器是否正确。





支持child/parent first设置(默认值)






默认值: javax.servlet,org.apache.commons.logging














1. UseJBossWebLoader=false时,过滤packages才能生效

2. UseJBossWebLoader=true时,不支持过滤packages

3. jboss 5.0以后UseJBossWebLoader参数将不支持

1. 在执行child/parent判断之前,会委托system classloader装载系统class,比如jdk的lib库

1. 多了一个serverclass配置,如果是serverclass优先采用child first

2. systemclass默认的配置,多了javax,org.xml,org.w3c配置。


svn url :


svn url :


svn url :

classloader 官方文档:


Static doesn't quite mean "shared by all instances" - it means "not related to a particular instance at all". In other words, you could get at the static field in class A without ever creating any instances.

As for running two programs within the same JVM - it really depends on exactly what you mean by "running two programs". The static field is effectively associated with the class object, which is in turn associated with a classloader. So if these two programs use separate classloader instances, you'll have two independent static variables. If they both use the same classloader, then there'll only be one so they'll see each other's changes.

As for an alternative - there are various options. One is to pass the reference to the "shared" object to the constructor of each object you create which needs it. It will then need to store that reference for later. This can be a bit of a pain and suck up a bit more memory than a static approach, but it does make for easy testability.





Continue reading 静态字段,classloader,web容器

it-e-05 Air floating displays

Todays display technologies form a field of huge interest as they are evolving with big steps while expanding the range of their applications following the demands of the market. Two new display technologies, which are still in development, impress us mostly for their concept and not so much for their display quality or their potential applications.
Fog Screen company suggests a screen created by a thick layer of fog, formed in between of two air surfaces of smooth flow. The FogScreen works very much like an ordinary screen in terms of projection properties. It can be used for both back and front projection. This kind of screens allow the projection of very impressive images, while the viewer can walk through the screen, walk directly into the images, and through them! The fog used is dry, so it doesn't make you wet even if you stay under the Fog Screen device for a long time. The fog is made of ordinary water with no chemicals whatsoever. The screen is supported by projectors with brightness of at least 3,000 ANSI Lumens and for the best result, a dark background is highly recommended.
The world premiere demonstration of FogScreen was at the Science Fair in Turku, Finland in October 2002, and its researchers are awarded for their discovery. Its first installations have already been made in museums in France and Finland and it has recently been produced to the U.S.A in the form of interactive screen.

A relevant technology is being developed by the "IO2 Technologies" company. Known by the name "Heliodisplay", this technology uses a device that displays on a bed of air above it. Nothing is added to the air so there is not any harmful gas or liquid emitted from the device, and nothing needs to be refilled. The device produces interactive images, which means it can be used as a "floating touch screen". In the course of developing the technology, Heliodisplays have been built that display images ranging from 5" to 42" and it is estimated that it can reach 150". Like the FogScreen, Heliodisplay is best viewed in dark backgrounds. Although Heliodisplay is plug-and-play compatible with most video sources (TV, DVD, computer, videogame, etc.) and anything can be projected on the FogScreen, both screen technologies are not meant to substitute computer or television screens. Their basic application fields include projections in board meetings and presentations, trade shows, museum, theme parks etc.

Continue reading it-e-05 Air floating displays

it-e-06 System Software

Software refers to computer programs. Programs are the instructions that tell the computer how to process data into the form you want. There are two kinds of software: system software and application software.
System software is a collection of programs that enables application software to run on a computer system's hardware devices, it is background software and includes programs that help the computer manage its own internal resources.
Application software is a specialized programs that enables the user to accomplish specific tasks. In this text, we mainly discuss system software.
System software consists of four kinds of programs: bootstrap loader, diagnostic routines,basic input-output system, and operating system. Among these four parts, the operating system is we most concerned with, whith helps manage computer resources. Most important operating systems are: Windows, Windows NT, OS/2, Macintosh, and Unix.

Windows gets its name because of its ability to run multiple applications at the same time, each in its own window. Windows offers graphical user interface (GUI), presents the user with graphic images of computer functions and data. It provides a standard mechanism for copying or moving information from one program to another. This mechanism, called the Clipboard, means that information created in one context is instantly reusable in another, you don't need to reenter information or work with clumsy data-transfer utilities. Windows also has DDE (dynamic data exchange) and OLE (object linking and embedding) functions. In DDE two or more applications can be linked. This way, data created in one application is automatically entered into the others. OLE, like DDE, links data between applications. Additionally, OLE allows the application receiving the data to directly access the application that created the data.
Windows NT

Windows NT is an operating system designed to run on a wide range of
powerful computers and microcomputers. It is a very sophisticated and powerful operation system. Developed by Microsoft, Windows NT is not considered a replacement for Windows.
[1]Rather, it is an advanced alternative designed for very powerful microcomputers and networks. Windows NT has two major advantages when compare to Windows:
Multiprocessing It is similar to multitasking except that the applications are run independently at the same time. For instance, you could be printing a word processing document and using a database management program at the same time. [2]With multitasking, the speed at which the document is printed is affected by the demands of the database management program. With multiprocessing, the demands of the database management program do not affect the printing of the document.Networking In many business environments, workers often use computer to communicate with one another and to share software using a network. This is made possible and controlled by special system software. Windows NT has network capabilities and security checks built into the operating system. This makes network installation and use relatively easy. OS/2 OS/2 stands for Operating System/2. It was developed jointly by IBM and Microsoft
Corporation. OS/2 has many similarities with Windows NT. It is designed for very powerful microcomputers and has several advanced features. Some of its advantages over Windows NT
Minimum system configuration Like Windows NT, OS/2 requires significant memory
and hard disk space. However, OS/2 requires slightly less.
Windows application Like Windows NT, OS/2 does not have a large number of
application programs written especially for it. OS/2 can also run Windows programs, but it runs these programs slightly faster than Windows NT.
Common user interface Microcomputer application programs written specifically for
Windows NT, as well as for OS/2, have consistent graphics interfaces. Across applications, the user is provided with similar screen displays, menus, and operations. Additionally, OS/2 offers a consistent interface with mainframes, minicomputers, and microcomputers. Macintosh Operation System The Macintosh Software, which runs only on Macintosh computers, offers a high-quality graphical user interface and is very easy to use. Apple Macintosh System 7.5 designed for Apple computers using Motorola's PowerPC microprocessor, is a significant milestone for Apple. It is a very powerful operating system like Windows NT and OS/2. System 7.5 has  network capabilities and can read Windows and OS/2 files. It has several

Ease of use The graphical user interface has made the Macintosh popular with many
newcomers to computing. This because it is easy to learn.
Quality graphics Macintosh has established a high standard for graphics processing. This is a principal reason why the Macintosh is popular for desktop publishing. Users are easily able to merge pictorial and text materials to produce nearly professional-looking newsletters, advertisements, and the like.

Consistent interfaces Macintosh applications have a consistent graphics interface. Across all applications, the user is provided with similar screen displays, menus, and operations. Multitasking Like Windows, Windows NT, and OS//2, the Macintosh System enables you to do multitasking. That is, several programs can run at the same time.
Communications between programs The Macintosh system allows applications programs
to share data and commands with other applications programs.

Unix was originally developed by AT&T for minicomputers and is very good for
multitasking. It is also good for networking between computers. Unix initially became popular in industry because for many years AT&T licensed the system to universities for a nominal fee. It is popular among engineers and technical people, with the arrival of very powerful microcomputers, Unix is becoming a larger player in the microcomputer world. Unix can be used with different types of computer systems, that is, it is a portable operating system. It is used with microcomputers,
minicomputers, mainframes, and supercomputers. The other operating systems are designed for microcomputers and are not nearly as portable. It also has the advantages of multitasking, multiprocessing, multiuser, and networking.

Continue reading it-e-06 System Software


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