2.2 OPERATING SYSTEM

 

2.2  OPERATING SYSTEM

2.2.1  Windows 2000

With each new release of Windows, Microsoft gives you new and inventive technologies to build more useful, manageable, and scalable networks. Windows 2000 (formerly Windows NT 5.0) is no exception. In fact, it is the most innovative release to date. There are four separate products that form the Windows 2000 line of operating systems.

·    Windows 2000 Professional: Replaces NT 4.0 Workstation. It is Microsoft 's flagship desktop operating system.

·    Windows 2000 Server: Replaces NT 4.0 Server installations, it support two-way symmetric multiprocessing (SMP). Upgrades from NT 4.0 Server support four-way SMP.

·    Windows 2000 Advanced Server: Replaces NT 4.0 Server Enterprise Edition. New installations support four-way SMP. Upgrades from NT 4.0 Server Enterprise Edition support eight-way SMP. Like its predecessor, Advanced Server supports large physical memories, clustering, and load balancing.

·    Windows 2000 Datacenter Server: A new Microsoft offering. It supports sixteen-way SMP, up to 64 GB of physical memory, clustering, and load balancing.

Each of these products includes key advancements that change how you plan, design, and deploy Microsoft networks. To employ such groundbreaking features as Active Directory, Dynamic DNS (DDNS), and IntelliMirror, you will need to plan ahead. To help you build your roadmap from Windows NT to Windows 2000, we offer an overview of the key Windows 2000 technologies and services. These advances are detailed in the sections that follow:

·    Active Directory.

·    Security.

·    Storage.

·    Networking.

·    Enterprise Management.

1. Active Directory

Can you effectively manage every resource in your network with a single logon? Do your users have a meaningful view of these resources? Was it easy for you to build a large, complex, international network with Windows NT? If you're bound by the limits of down-level (NT 3.x-4.0) networks, your answer is probably no—at least not without some headaches.

Microsoft networks that are built with Active Directory can help you when you meet these challenges. Unlike down-level directory services, which are flat, Active Directory is hierarchical. Active Directory stores each of your company's resources logically, forming a tree structure that mirrors your enterprise. Every resource in even the largest networks is easy to find and manage.

2. Security

The cornerstone of Windows 2000 security is Active Directory. Its support for granular- access control, inheritance, and delegation of administrative task gives you the flexibility to secure resources without compromising your network's purpose. Fine-granted access control is not offered in NT 3.x or 4.0. This often forces you to assign permissions that give either too little or too much control. Although Active Directory should be a significant piece of Windows 2000 security strategy, it can not deliver complete enterprise security by itself.

3. Storage

The Encrypting File System (EFS) would not be possible without extensions to NTFS. New Technology File System (NTFS) 5.0 is the foundation for several enhancement in Windows 2000. Sharing and managing your company's data is top priority. You must gain complete control of storage to be a successful administrator.

4. Networking

Storage innovations give you improved tools to manage and share resources. The improvements to networking in Windows 2000 are equally groundbreaking. For example, you have the opportunity in Windows 2000 to remove all NetBIOS traffic from your network. The Dynamic Domain Name System (DDNS) can entirely eliminate your dependence on NetBIOS and WINS. Also, you can now build more secure Virtual Private Networks (VPNs) that leverage PK cryptography. Further, support for Quality of Service (QoS)—a policy-based bandwidth management technology—is added. Some of the topics covered in this section are new in Windows 2000, others represent improvement to existing technologies.

5. Enterprise Management

Along with its advances in directory management, security, public key cryptography, storage, and networking, Windows 2000 includes improvement in enterprise management. Total Cost of Ownership (TCO) is a leading concern shared by many companies. After you deploy a particular technology, a TCO study will consider the cost of maintaining (or owning). In corporate networks, most TCO efforts are aimed at reducing the expense of managing desktops.

2.2.2  Windows XP

Windows XP is the next version of Microsoft Windows beyond Windows 2000 and Windows Millennium. Windows XP brings the convergence of Windows operating systems by integrating the strengths of Windows 2000—standards-based security, manageability and reliability with the best features of Windows 98 and Windows Me—Plug and Play , easy-to-use user interface, and innovative support services to create the best Windows yet.

1. Intelligent User Interface

While maintaining the core of Windows 2000, Windows XP features a fresh new visual design. Common tasks have been consolidated, and simplified, and new visual cues have been added to help you navigate your computer more easily. This section introduces the innovations in the user interface that make it easier to use your computer at work or at home.

（1）Fast User Switching for multiple users of a computer.

Designed for the home, Fast User Switching lets everyone use a single computer as if it were his or her own. There is no need to log someone else off and have to decide whether to save another user's files. Instead Windows XP takes advantage of Terminal Services technology and runs each user session as a unique Terminal Services session, enabling each user's data to be entirely separated.

Enabled by default if you're using Windows XP Home Edition, Fast User Switching is also available on Windows XP Professional if you install it on a stand alone or workgroup-connected computer. If you join a domain with a computer running Windows XP Professional, you will not be able to use Fast User Switching.

Fast User Switching makes it easier for families to share a single computer. For example, if a mother uses the computer to work on finances and has to leave for a short period of time, her son can switch to his own account and play a game. The financial application is left running and open in the mother's account. All of this is done without logging off. Switching users is easy with the new Welcome screen easily customizable with pictures for each user who logs on to the computer.

（2）New Visual Style.

Windows XP has new visual styles and themes that use sharp 24-bit color icons and unique colors that it can be easily related to specific tasks. For example, green represents tasks that enable you to do something or go somewhere, such as the Start menu.

（3）Redesigned Start Menu.

The Start menu was designed to adapt to the way you work. Your five favorite programs display first, and your default E-mail and Web browser are always avai1able. It groups your most frequently used files and applications together for quick and easy access. One click also gets you to Help and Support, and tools to configure your system. In addition, you can further customize the Start menu to suit your needs.

（4）Search Companion.

Windows XP makes it easier to search by grouping search related tasks into a Search Companion.

（5）My Documents.

Windows XP makes it easy to keep track of your files by letting you arrange them in various groups. You can view your documents by type. You can also group files according to the last time you modified them such as today, yesterday, last week, two months ago, earlier this year, or last year.

（6）Webview.

Windows XP uses webview technology helping you better manage flies and the file namespace. For example, if you select a file or folder, you see a list of options allowing you to rename, move, copy, e-mail, remove it, or publish to the Web. This functionality is similar to what you see in Windows 2000 if you right-click on a file or folder; Windows XP takes this information and brings it into view directly on the desktop.

（7）File grouping.

Windows XP introduces an easier-to-manage taskbar by grouping multiple instances of the same application. For example, instead of having nine instances of a Microsoft Word file each arranged horizontally on the taskbar, Windows XP groups them together on one taskbar button. In this scenario, you see only one taskbar button, showing the number of files that are open for the application. Clicking the button shows the vertical list of all file names. In addition, the files can all be cascaded, tiled, or minimized at the same time.

（8）User interface enhances productivity.

The new user interface takes the Windows operating system to a new level of usability, enabling you to complete tasks more easily and faster than ever before. The rest of this paper highlights new technologies in Windows XP.

2. Comprehensive Digital Media Support

（1）Windows Media Player 8.

Windows XP features Windows Media Player 8, which brings together common digital media activities including CD and DVD playback, jukebox management and recording, audio CD creation, Internet radio playback, and media transfer to portable devices.

Windows Media Player 8 includes new features such as DVD video playback with rich media information and full screen controls, CD-to-PC music copying and automatic conversion of MP3 files. Windows Media Audio 8 provides nearly three times the music storage of MP3 with faster audio CD burning and intelligent media tracking for more control over digital media. Within Windows XP the new “My Music” folder makes common music tasks easier to perform.

In addition, Windows Media Player 8 includes the following.

·    Ability to lock down Windows Media Player features in a managed network: WindowsMedia player has a standard corporate skin that can be deployed in a network. If the Active Directory^? service is enabled, administrators can specify a corporate skin, restrict playback formats and codices, and specify other customizations on a per-group or per-user basis (This requires client computers to run Windows XP Professional).

·    Digital broadcast support: Supports analog and digital TV (including HDTV), This includes signal demodulation, tuning, software de-multiplexing, and guide store. In addition you can enable IP data broadcasting such as extract steams from a digital TV signal.

·    Accelerated video rendering：Standardized MPEG-2 video acceleration provides smootherand faster playback using a subset of DirectX^? APIs.

·    Video mixing renderer：This supports alpha blending letting you phase multiple videos, overlay them, or integrate close captioning of text. Video is treated as a texture and can take advantage of 3D graphics. For example, you could overlay videos on each side of a cube as it rotates.

·    Expanded support for more audio cards and their features: For example, card man-
ufacturers can provide support for Dolby Digital.

（2）Windows Movie Maker.

Windows Movie Maker version 1.1 provides base-level features for Windows Media capture and file creation, simple editing of video and audio, and the saving and publishing of Windows Media files. Although the utility produces output only in the Windows Media format, it will import all file formats and compression types supported by the DirectShow architecture.

If your computer does not contain my video capture hardware, all other non-video capture-related features of the application are fully functional and they allow for the importing and editing of media assets that exist on your computer.

Windows Movie Maker has many practical uses. If you want to archive your home video library collection onto the hard drive of a PC, you can record, edit, organize, and share the home video library from a PC. You could also share the home video with family and friends via e-mail or over the Web. If you want to make a video slide show, you can combine still images and publish into a Windows Media format.

（3）Digital Photo Support.

Windows XP makes it easier to use digital devices and provides many options to manipulate images such as publishing pictures to the Web, e-mailing photos (with an option of compressing them for you for smaller file size), displaying pictures in an automatic slideshow, and allowing you to zoom in on images.

2.2.3 Linux

Linux is a clone of the UNIX operating system that runs on Intel 80x86-based machines, where x is 3 or higher. Linux is also very portable and flexible because it has now been ported to DEC Alpha, PowerPC, and even Macintosh machines. And progress is being made daily by Linux enthusiasts all over the world to make this free operating system available to all the popular computing machines in use today. Because the source code for the entire Linux operating system is freely available, developers can spend time actually porting the code instead of wondering about whom to pay benefit licensing fees.

Documentation for the many parts of Linux is not very far away, either. The Linux Documentation Project (LDP) is an effort put together by many dedicated and very smart individuals to provide up-to-date, technically valuable information. All of this LDP information can be found on the Internet at various Linux source repositories, Each “HOWTO” document for Linux is the result of effort from many Linux enthusiasts. The original authors of these documents are usually also the core Linux developers who have put in hours of time and effort while struggling with new features of Linux. These individuals are the ones who deserve the credit.

1. What Is Linux

Linux is a free UNIX clone that supports a wide range of software such as TeX, X Window Systems, the GNU C/C++ compiler, and TCP/IP. It 's a versatile, very UNIX-like implementation of UNIX, freely distributed by the terms of the GNU General Public License. Linux is also very closely compliant with the POSIX.1 standard, so porting applications between Linux and UNIX systems is a snap.

New users of UNIX and Linux might be a bit intimidated by the size and apparent complexity of the system before them. Many good books on using UNIX and Linux are available, for all levels of expertise ranging from novice to expert.

Although 95 percent of using Linux is exactly like using other UNIX systems, the most straightforward way to get going on your new system is with a book tailored for Linux.

2. Linux Versus UNIX

Linux is not a trademark and has no connection to the trademark UNIX. UNIX is one of the most popular operating systems worldwide because of its large support base and distribution. It was originally developed as a multitasking system for minicomputers and mainframes in the mid-1970s, but it has since grown to become one of the most widely used operating systems anywhere, despite its sometimes confusing interface and lack of central standardization.

3. What Do I Get with a Linux System

Linux is a freely available and distributable look-alike of UNIX developed primarily by Linus Torvalds at the University of Helsinki in Finland. Linux was further developed with the help of many UNIX programmers and wizards across the Internet.

Linux is small, fast, and flexible. Linux has been publicly available since about November 1991. Version 0.10 went out at that time, and version 0.11 followed in December 1991. There are very few small bugs now, and in its current state, Linux is most useful for people who are willing to port and write new code.

Linux is in a constant state of development. Linux is cheaper to get than most commercially available UNIX systems. If you have the patience and access to the Internet, the only price you pay for Linux is your time. For a nominal fee of anywhere from U.S.$30 to U.S.$200, you can save yourself some time and get CD-ROM or floppy-disk distributions from several commercial vendors. In my opinion, the most important advantage of using Linux is that you get to work with a real kernel. All the kernel source code is available for Linux, and you have the ability to modify it to suit your needs. Looking at the kernel code is an educational experience in itself.

KEYWORDS

NOTES

（1）SMP（对称多任务处理）。一种计算机体系结构，多个处理器共享同一内存。内存中含有操作系统和所有当前运行的应用程序及数据的副本。因为操作系统将作业分成多个任务并将任务分配到空闲的处理器，所以SMP减少了事务处理时间。

（2）VPN（虚拟专用网络）。在Internet等公用网络上的一些节点的集合。为保证信息的安全性，采用了密码技术来相互通信以防止未授权的用户截取并读懂这些信息，就好像这些节点是用专线连接起来的一样。

（3）public key（公用密钥）。公用密钥加密系统中的一对密钥之一。用户将该密钥发放给公众，用来给发送到用户的消息加密及解密用户的数字签名。

（4）Web（万维网）。在全世界范围内，所有位于HTTP服务器上相互链接的超文本文档。位于WWW上的文档称为页面或Web页面，用HTML语言编写，并使用URL进行标识，URL指明了特定的计算机和路径名，用户通过它可对文件进行访问，并在HTTP协议下将文件在节点间进行传输，直至传输到最终用户。嵌入到HTML文档中的代码可以与含URL的文档中的特定单词或图像相关联，以使得用户可访问其他文件，也许只是一个击键或鼠标单击动作，用户就已到达世界的其他位置。这些文件中可以包含文本、图形、影像文件、声音、Java小程序、ActiveX控件或其他一些嵌入式小程序，当用户通过单击链接激活这些小程序时，这些小程序就会执行。访问Web页面的用户也可以从FTP站点上下载文件，同时还能使用Web页面上的链接通过电子邮件向其他用户发送消息。WWW是在1989年由欧洲粒子物理实验室（CERN）的Timothy Berners-Lee发明的。

（5）browser（浏览器）。一种客户端应用程序，它允许用户查看位于WWW、另一网络以及用户计算机上的HTML文档；允许用户沿着文档中的超链接进行浏览或传输文件。基于文本的Web浏览器可以通过shell账户向用户提供服务，但它只能显示HTML文档中的文本元素。然而，大部分的Web浏览器要求具有一个可以处理IP数据包的连接，同时，它还可以显示文档中的图形，播放音频和视频文件，并可以执行一些小程序，例如：Java applet和ActiveX控件等，而且都可以嵌入到HTML文档中。有些Web浏览器则需要有辅助应用程序或插件才能完成这些任务。另外，目前大多数的Web浏览器也允许用户发送和接收电子邮件以及阅读和响应新闻组。

（6）folder（文件夹）。在Mac OS、Windows和其他操作系统中，在图形用户界面中放置程序和文件的容器。在屏幕上用一个文件夹的图形（图标）表示。这种容器在其他操作系统中，如MS-DOS和UNIX中称做目录。文件夹可以用于组织磁盘上的程序和文档，它既可以含有文件，也可含有其他文件夹。

（7）format（格式化）。将磁盘的存储空间分成不同的数据“隔断”，并且每个“隔断”都可以被操作系统定位，其中的数据可被排序和检索。准备这样的磁盘的过程称做格式化。当格式化使用过的磁盘时，所有格式化前在磁盘上保存的数据都会丢失。

（8）IP（Internet协议，网际协议）。Internet Protocol的首字母缩略词。TCP/IP中的协议，负责将数据消息拆分为包，并将这些包从发送者按一定路径传输到目的网络或站点，然后在目的地将包重新组合成原始的数据消息。IP对应于ISO/OSI模型中的网络层。

（9）MPEG（运动图像专家组）。由联合ISO/IEC技术委员会信息技术分会建立的音频和视频压缩标准集。运动图像专家组标准针对不同的状态设计有不同的类型。

（10）API（应用程序编程接口，应用程序接口）。由计算机操作系统提供的一系列例程，应用程序调用这些例程可实现一系列的操作。

（11）GPL（公用授权协议）。通用公共许可协议免费软件基金组织分发软件所遵循的协议。任何拥有这种软件的人可向其他团体分发该软件，并可收取软件分发和技术服务费用，但不能限制其他团体也这样做。用户可以更改该程序，不过如果要分发更改后的版本，则需要清楚地说明更改之处，并且更改后的版本也在该协议管理范围之内。软件分发者必须提供源代码或说明从何处可得到源代码。

EXERCISES

1. Multiple choices.

（1）The Windows 2000 product line includes        .

A．Windows 2000 Professional

B．Windows 2000 Server

C．Windows 2000 Advanced Server

D．Windows 2000 Datacenter Server

（2）Windows 2000 Server can support           .

A．two-way SMP                              B．four-way SMP

C．eight-way SMP                                   D．sixteen-way SMP

（3）Windows 2000 has the key technologies, they are              .

A．active directory                                   B．security

C．flat directory                                D．enterprise management

（4）Active Directory can help you                 .

A．deliver complete enterprise security by itself

B．build a complex international network

C．manage every resource with a single logon

D．get off the limits of down level networks

（5）Active Directory supports               .

A．granular access control                         B．encapsulation

C．delegation of administrative task           D．inheritance

2. Translate these sentences from English into Chinese.

（1）Fast user switching makes it easier for families to share a single computer.

（2）The Start menu was designed to adapt to the way you work.

（3）Your five favorite programs display first, and your default e-mail and Web browser are always available.

（4）Windows XP makes it easy to keep track of your files by letting you arrange them in various groups.

（5）Within Windows XP, the new “My Music” folder makes common music tasks easier to perform.

3. Fill in the blank with appropriate words or phrases.

（1）Linux is a        of the UNIX operating system.

（2）Linux is very        .

（3）Linux is a        operating system.

（4）        of Linux is freely available.

（5）We can find LDP information on the        .

（6）Porting application between Linux and UNIX systems is a        .

（7）We could be intimidated by the         complexity of UNIX and Linux.

（8）The most important advantage of using Linux is to work with a        .

（9）Linux is a       system.

（10）UNIX is one of the most popular operating systems due to its large support        .

A．multitasking

B．size and apparent

C．Internet

D．clone

E．base and distribution

F．portable and flexible

G．real kernel

H．snap

I．source

J．free

READING MATERIALS

Macintosh OS X

1. Introduction to Macintosh OS X

Mac OS X is a modern operating system that uses the power and stability of UNIX. Mac OS X uses the GUI called Aqua. Aqua includes a new Finder and the Dock designed to help navigate and organize your system, and give you access to your most frequently used applications, folders, and minimized windows. Mac OS X is a multi-user operating system with both administrative and user accounts.

2. The Finder

The Finder is to Macintosh what Windows Explorer is to Microsoft Windows. It allows you to navigate around your computer, view and access its contents.

There are three ways to view items in the Finder.

（1）By icon (Fig.2-2).

Fig. 2-2  By icon

（2）By list (Fig. 2-3).

Fig. 2-3  By list

（3）By path (Fig. 2-4).

Fig. 2-4  By path

3. The Dock

You may also use the Dock (Fig.2-5). The Dock is a handy launching pad that gives you quick access to your favorite applications, destinations and more.

Fig. 2-5  The Dock

The Dock can be positioned on the bottom, left or right of your screen.

You can add or subtract any icon in the Dock by dragging it into or out of the Dock. Launch any application by clicking on its icon in the Dock. A small black triangle below an application icon indicates that it is currently running. View the contents of any folder in the Dock by holding down the mouse button over the folder.

Control of the Dock can be found under the Apple Menu in the upper left corner of your screen or in System Preferences (Fig. 2-6).

 

Fig. 2-6  Apple Menu

4. System Preferences

System Preferences take the place of Control Panels in earlier versions of the Mac OS. You can access the System Preferences via the Dock or the Applications folder (as shown in Fig. 2-7).

Fig. 2-7  System Preferences

（1）Login.

Login allows you to determine if a login name and password will be required or automatically log in. It also lets you determine what items will load at start up.

（2）Internet.

Internet lets you set default applications for email, web browser and news reader. It also lets you set start pages in your browser. If you have multiple users on your computer you can set preferences for each user.

（3）Network.

Network allows configuration of TCP/IP and AppleTalk. You can also select which port you will configure such as Ethernet, modem or AirPort.

（4）Classic.

Classic is an environment for running Mac OS 9 applications. It starts automatically when a classic application is launched or it can be started in the Classic System Preference. You can also set classic to load at startup.

（5）Startup Disk.

Startup disk allows you to select the operating system on which your computer will start (Mac OS 9 or X) or which bootable volume will be used at startup.

（6）Users.

Users allows you to create and give rights to users if you have a multi-user computer environment.

（7）Printing.

Printing is controlled via the Print Center application found in Applications/Utilities. You can choose AppleTalk printers, access printers via IP address or select a local USB printer, As shown in Fig. 2-8.

Fig. 2-8  Choose AppleTalk

For more information on printing under Mac OS X see the Macintosh documents page at http://www.itc.virginia.edu/desktop/mac.

（8）Internet Connect.

The Internet Connect application has replaced Remote Access as the method of connecting to the Internet via modem. You can find Internet Connect in the Applications folder. When you open Internet Connect you can select from connection configurations you have created, As shown in Fig. 2-9.

Fig. 2-9  Connection Configurations

You can create or edit dialup configurations in Network Preferences (Fig. 2-10).

Each dialup configuration can have specific options. For example, click on PPP Options (See Fig. 2-11).

Fig. 2-10  dialup configurations

Fig. 2-11  specific options

Below is a complete listing of Mac OS X documents:

·    Macintosh Network Connectivity.

·    AirPort Configuration for OS X.

·    LDAP solution for OS X.

·    Netscape 7.2.

·    OS X Ethernet configuration guide.

·    OS X Printing configuration guide.

·    Internet Connect (Remote Access for Mac OS X).

·    Home Directory Service for Macintosh.

·    Fetch.

·    Secure Telnet.

OPERATING SYSTEM PLATFORM

The type of processor used in a computer determines the type of machine language it uses。And the computer's operating system is created to work with that particular type of machine language. Thus, the processor model and the operating system determine the platform—that is, the type of computer architecture, or family; the PC and the Apple Macintosh are two common platforms. For the most part, software created for one type of platform will not run, without special arrangements, on other platform.

Common operating systems used on mainframes and midsize computers are MVS, VM, OS/390, and VAX/VMS. In the section, we describe the following microcomputer operating system.

1. DOS and Windows 3.X

Command-driven DOS—short for Disk Operating system—was very popular in the 1980s and eariy 1990s. IBM's version of DOS is called PC-DOS and Microsoft's version is called MS-DOS. Except for subtle differences, PC-DOS and MS-DOS are identical. The initial version, DOS 1.0, was released in August 1981. It consisted of 4000 lines of assembly-language source code and ran in 8 KB of memory by using the Intel 8086 microprocessor.

When IBM developed a hard-disk-based personal computer, the PC/XT, Microsoft developedDOS 2.0, released in 1983. It contained support for the hard disk and provided for hierarchical directories. Heretofore, a disk could contain only one directory of files and support a maximum of 64 files. Although this was adequate in the era of floppy disks, it was too limited for a hard disk, and the single-directory restriction was too clumsy. The new release allowed directories to contain subdirectories as well as files. The new release also contained a richer set of commands embedded in the operating system to provide functions that had to be performed by external programs provided as utilities with release 1. Among the capabilities added were several UNIX-like features, such as I/O redirection, which is the ability to change the input or output identity for a given application, and background printing. The memory-resident portion grew to 24 KB.

When IBM announced the PC/AT in 1984, Microsoft introduced DOS 3.0. The AT contained the Intel 80286 processor, which provided extended addressing and memory-protection features. These were not used by DOS. To remain compatible with previous releases, the operating system simply used the 80286 as a “fast 8086”. The operating system did provide support for new keyboard and hard-disk peripherals. Even so, the memory requirement grew to 36 KB. There were several notable upgrades to the 3.0 release. DOS 3.1, released in 1984, contained support for networking of PC. The size of the resident portion did not change; this was achieved by increasing the amount of the operating system that could be swapped. DOS 3.3, released in 1987, provided support for the new line of IBM machines, the PS/2. Again, this release did not take advantage of the processor capabilities of the PS/2, provided by the 80286 and the 32-bit 80386 chips. The resident portion at this stage had grown to a minimum of 46 KB, with more required if certain optional extensions were selected. DOS 7.0 was issued in l996 and includes enhanced support for managing networks and the latest microprocessors.

By this time, DOS was being used in an environment far beyond its capabilities. The introduction of the 80486 and then the Intel Pentium chip provided power and features that simply could not be exploited by the simple-minded DOS. Meanwhile, beginning in the early 1980s, Microsoft has begun development of a graphical user interface (GUI) that would be interposed between the user and DOS.

In l985, Microsoft released Windows 1.0, an operating environment that lays a graphical user interface shell around DOS and extends DOS's capabilities. Version 2.0 was released in 1988, but it wasn't until version 3.0 was released in l990 that Windows really took off and created an industry tied to its GUL multitasking capabilities, and ability to manage large amounts of memory. There have been several releases of Windows 3.0, 3.1, and 3.11. With Windows 3.x you display your work in one or more windows on the desktop. You can easily switch and move data among windows. Although Windows 3.x improves DOS's capabilities, DOS still has many shortcomings and has been succeeded by other, more versatile operating systems. Windows 3.x is becoming obsolete, replaced by Windows 9x and later versions.

2. Windows 9x

Windows 95, released in 1995, was the major upgrade designed to replace DOS and Windows 3.x. A true multitasking operating system, Windows 95 does not require the separate MS-DOS program. The GUI is not the shell; instead it is integrated into the operating system. Like Windows 3.x, Windows 95 uses windows and a desktop. Among the many features included in Windows 95 are support for longer filenames, e-mail, fax transmission, multimedia, and Plug and Play, which simplifies the process of installing new hardware.

Most important, though, is the fact that Windows 95 is a 32-bit operating system, meaning that it can work with 32-bits of data at one time. This is twice as much as can be processed by my version of DOS, which can only work with data in l6-bit chunks. What this means to you is that applications written for Windows 95 run faster and you can work with multiple applications at the same time without a noticeable delay. Also, with Windows 95, you are able to realize the potential and power of today's more sophisticated microprocessors.

Windows 98, which models its interface after Windows 95, includes several enhanced capabilities over Windows 95—primarily, its support of the Internet. With Windows 98, you can open documents stored locally on your computer, documents stored on your company's network, and documents stored on the Web without having to open a separate web-browser window. In addition, Windows 98 provides support for huge hard disks, state-of-the-art hardware such as DVD disks and the Universal Serial Bus standards, and additional commands for customizing the user interface.

A simplified version of Windows 9x, Windows CE, is used for palmtop computers.

3. Windows NT/Windows 2000

Whereas Windows 9x basically is consumer-oriented, Window NT, for New Technology, is business-oriented. Providing a similar interface to Windows 9x, it is a multitasking, multipro-

cessing operating system with built-in support for large networks of computers—that is, WindowsNT is a multiuser system. Multiuser platforms support workgroup computing, situations in which LANs are set up to allow users to share files, databases, and applications. Windows NT 4.0 is designed to run on workstations or other computer systems. Windows NT 5.0 will work on new notebooks.

There are two basic versions of Windows NT. Windows NT Server, for heavy-duty networking, can support up to 32 processors, whereas Windows NT workstation supports 1～2 processors.

Windows 2000 combines the Windows NT line with Windows 9x. Indeed, Microsoft's goal is to produce the first operating system that runs everything from laptops to dumb terminals in networks to huge office computers.

4. OS/2 Warp

OS/2 was initially released in April 1987 as IBM's contender for the next mainstream operating system. OS/2 (Operating System 2) was designed to run on IBM and IBM-compatible microcomputers. Unfortunately, because of an array of management and marketing disasters, IBM slipped far behind Microsoft in developing an installed base for OS/2. In late 1994 IBM unveiled a souped-up version of OS/2, called OS/2 Warp. OS/2 Warp is similar to Windows NT. IBM has even started shipping Windows NT on some of its lower-end systems. Although the future of OS/2 Warp is uncertain, IBM continues to support its approximately 10 million Warp users. The latest versions of Warp are available online and can be downloaded from IBM's Web site.

UNIX OPERATING SYSTEM

1. History of UNIX

This section introduces to you a brief overview of the history of UNIX.

Written by Ken Thompson and Dennis Ritchie, developed at Bell Laboratories, USA, derived from Multics (1969). Thompson developed a new programming language “B”. Ritchie enhanced “B” to “C” and helped develop “UNIX”. Two flavors, SYSTEM V (Commercial, run by AT&T) and BSD (Educational, run by Bell Labs). Recent developments are graphical interfaces, MOTIF, X Windows, Open View.

Major suppliers today:

·    Sun Microsystems (SPARC).

·    Data General (AVION).

·    IBM (RS6000 AIX).

·    Hewlett Packard.

·    Santa Cruz Organization (SCO).

·    DEC.

A free UNIX system called Linux is also available for download from the Internet or available on CD-ROM.

2. Main Features of UNIX

At the time UNIX was introduced, some of these features set the UNIX operating system apart from other systems available at that time. Today, many of these features are commonplace.

·    Multi user, more than one user can use the machine at a time; supported via terminals (serial or network connection).

·    Multi tasking, more than one program can be run at a time.

·    Hierarchical directory structure, to support the organization and maintenance of files.

·    Portability, only the kernel (<10 percent) was written in assembler. This meant the operating system could be easily converted to run on different hardware tools for program development, a wide range of support tools (debuggers, compilers).

3. The Structure of the UNIX Operating System

This section outlines the basic structure of the UNIX operating system, as a division of three parts.

Kernel schedules programs, manages data/file access and storage, enforces security mechanisms, performs all hardware access.

Shell presents each user with a prompt, interprets commands typed by a user, executes user commands, and supports a custom environment for each user.

Utilities file management (rm, cat, ls, rmdir, mkdir), user management (passwd, chmod, chgrp), process management (kill, ps), printing (ip, troff, pr), and program development tools.

4. MultiUser Operating Systems

A multiuser operating system allows more than one user to share the same computer system at the same time. It does this by time-slicing the computer processor at regular intervals between the various users. The switching between user programs is done by part of the kerne1. To switch from one program to another, requires a regular timed interrupt event, saving the interrupted programs state and data, restoring the next programs state and data, running that program till the next timed interrupt occurs.

The timed event is usually about 1 to 10 milliseconds apart. It is generated by a real-time clock.

5. Handling Programs

Each computer has a maximum amount of memory (RAM) that is installed in the computer. Some of this memory is required by the operating system. The remainder is available to user programs. The more memory that can be provided in totals the better. Where there is insufficient main memory to run a users program, some other users program residing in main memory must be written out to the disk unit to create some free memory space. This process is called swapping. When the system becomes overloaded (where there are more users than the system can handle), the operating system spends most of its shuttling users programs between main memory and the disk unit, and users response time degrades. This is called disk thrashing and is overcome by installing more main memory.

6. Processes

Each program running on a UNIX system is called a process. When a user types a command, UNIX constructs a Process Control Block (PCB) for the process. Each process has a PCB that holds its priority, the process state, register information and additional details.

UNIX provides a set of utilities for managing processes.

·    PS—list processes.

·    KILL—kill a process.

·    $—run a process in the background.

If the system administrator found that a particular user was performing an operation that was consuming too much computing time or dominating a system resource such as a printer, they could use the PS command to identify the offending users process and then use the KILL command to terminate that process.

Each program is assigned a priority level. Higher priority tasks (like reading and writing to the disk) are performed more regularly. User programs may have their priority adjusted dynamically, upwards or downwards, depending upon their activity and available system resources.

Multi tasking system supports foreground and background tasks. A foreground task is one that the user interacts directly with using the keyboard and screen. A background task is one that runs in the background (it does not have access to the screen or keyboard). Background tasks are usually used for printing.

7. Running Programs in the Background

Let the user carry one more important task-examples are printing and formatting documents. The ampersand symbol (&) is appended to the command. The shell assigns a process number (pid) to the command. Background jobs can be deleted using the KILL command.