## 计算机代写|操作系统代写operating systems代考|CS140

statistics-lab™ 为您的留学生涯保驾护航 在代写操作系统operating systems方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写操作系统operating systems代写方面经验极为丰富，各种代写操作系统operating systems相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 计算机代写|操作系统代写operating systems代考|Network-Based Firewalls

A network-based firewall is a hardware device designed to protect you against the dangers of having an unprotected connection to the Internet. It sits between a private network and the Internet (or other network) and examines all traffic in and out of the network it is protecting. It will block any traffic it recognizes as a potential threat, using a variety of techniques. Table $2-1$ lists some of the most common technologies normally included in a firewall, although some of these are not strictly firewall technologies. Your ISP and most corporations employ hardware firewalls, expensive and specialized computers manufactured by companies such as Cisco, Palo Alto Networks, Fortinet, and others, and these sophisticated firewalls require highly trained people to manage them. Such a firewall probably protects the network at work or at school.

At home or in a small office, most people have a consumer-grade hardware firewall that comes in a small device that performs many of the same functions performed by a more professional-grade firewall. The most common name for these devices is broadband router or cable/DSL router. They combine the function of a firewall, a router (a device that “routes” traffic from one network to another), an Ethernet switch, and even a wireless access point all in one tiny box. These inexpensive devices can handle the traffic of just a few computers, while the more serious devices employed by ISPs and large organizations can handle thousands of simultaneous high-speed transmissions. These consumer-grade devices now come with the “one button” configuration that automatically configures a simple connection to the Internet, with the latest security turned on. You can also access the built-in Web page to make manual changes to the settings. Figure 2-7 shows the security page of a Cisco Wireless Router, which includes support for all the technologies listed in Table $2-1$ and many more features, including support for the $802.11 \mathrm{~N}$ standard for Wi-Fi communications and security. The setting labeled “Firewall” is just one option for securing your home network. Even with this device, you would need to research the impact of the various settings before changing from the default settings.

The firewall administrator configures a firewall to allow traffic into the private network or prohibit traffic from entering the private network based on the types of computers residing within the private network, and how they will interact with the Internet. If all the computers on a private network are desktop computers that connect to the Internet to browse Web pages and access FTP sites, the firewall protecting the network has a simple job. It simply blocks all in-bound traffic that is not the result of a request from a computer on the internal network; it matches incoming traffic with previous outgoing traffic that made requests that would result in incoming traffic. Then, when you connect to a website, outgoing traffic from your computer to the website requests to see a page. That page comes to you as incoming traffic and a firewall will allow it through based on your initial request.

But if the private network includes servers that offer services on the Internet, then the firewall must allow initiating traffic to come through, but it does not allow all incoming traffic through. In this case, an administrator configures a firewall to allow incoming traffic of the type that can only communicate with the internally based servers. The various types of traffic include email, Web, FTP, and others. Each type of traffic has a certain characteristic the firewall can recognize. Figure 2-8 shows a firewall protecting a network containing both servers and desktop computers (shown as clients).

## 计算机代写|操作系统代写operating systems代考|Antispam Software

A spam filter is software designed to combat spam by examining incoming email messages and filtering out those that have characteristics of spam, including certain identified keywords. In an organization with centralized network and computer management, spam filter software installed on central mail servers can remove spam before it gets to a user’s desktop. Network administrators may use Internet=based spam filtering services that block spam before it reaches the corporate network.

Individuals connected to the Internet from home or in small businesses are often on their own when it comes to eliminating spam. Luckily, many email clients, such as Microsoft Outlook, offer spam filtering. Without a spam filter you must sort through your own email to find and delete the spam. Spam filters are not perfect-they can filter out legitimate messages, while allowing some spam messages through. For this reason, most spam filters require some configuration on the part of the user using rules or filters that will automate the process of removing spam from known sources. And the user will still often need to review a list of suspected spam messages. Figure 2-12 shows the Microsoft Outlook Junk Email Options dialog box with several tabbed pages of settings that allow you to configure the spam filter.

An antivirus program can examine the contents of a storage device or RAM looking for hidden viruses and files that may act as hosts for virus code. Effective antivirus products not only detect and remove viruses, but they also help you recover data that has been lost because of a virus. To remain current, they require frequent updating as to the virus threats to watch for. An antivirus program includes an antivirus engine (the main program) and a set of patterns of recognized viruses. usually contained in files called definition files. Retailers of antivirus software commonly charge an annual fee for updates to the antivirus engine and the definition files. There are excellent free services for home users. One example is AVG antivirus from GRIsoft. Software companies that offer free security software usually also offer a feature-rich commercial version to which you can upgrade for a fee. The free version gives you a chance to see if you like using it before you put out any money. Once installed, most antivirus programs will automatically connect to the manufacturer’s website and check for these updates.

. sh

. sh

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

## 计算机代写|操作系统代写operating systems代考|CS6200

statistics-lab™ 为您的留学生涯保驾护航 在代写操作系统operating systems方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写操作系统operating systems代写方面经验极为丰富，各种代写操作系统operating systems相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 计算机代写|操作系统代写operating systems代考|Today’s Desktop Operating Systems

Today’s desktop microcomputer operating systems include Windows 7 , Windows 8 , Windows 10 , macOS, Chrome OS, and Linux. All of these OSs are multiuser/multitasking operating systems, with support for virtual memory and security. Each comes in versions that support either 32-bit or 64-bit processors.

Table 1-1 summarizes the current desktop OSs covered in later chapters of this book, listing the publisher, platform, and types of applications that you can run natively on each OS.

What follows is a brief description of these OSs, with more detail in the chapters devoted to each OS.

Released in October 2009, Windows 7 includes several improvements correcting the shortcomings that kept Windows Vista from being widely accepted. Windows 7 is faster than Windows Vista in several ways, from starting up, to going into and out of sleep mode, to recognizing new devices when you connect them. Windows 7 has many new features. The short list includes a redesigned desktop (see Figure 1-11) with a new taskbar that has many new features of its own, such as jump lists. Learn more about Windows 7 in Chapter 4.

Windows 8 , released in October 2012 , came with better security and improved wireless connectivity as well as support for some newer hardware, such as USB $3.0$ ports and improved touch screen support for simultaneous multiple touches and gestures.

The most controversial changes to Windows 8 were to the GUI, or rather GUIs. The default GUI, centered around the Start screen shown in Figure 1-12, is a departure from the Windows 7 desktop with its three-dimensional look. Objects in this new GUI appear flat, without shading and borders so that they do not take up extra screen space. This is necessary because Windows 8 runs on a wide range of computing devices: PCs, laptops, and tablets. The Windows 8 Start screen contains tiles that represent apps. Each tile can show active content, such as newsfeeds, stock quotes, slideshows, and more, depending on the tile’s app.

The second Windows 8 GUI, a modified version of the Windows 7 desktop (without the Start menu) has a very flat look to it in spite of having overlapping windows. Figure 1-13 shows the Windows 8 desktop. In 2013, Microsoft released an update to Windows 8 -Windows $8.1$ – with changes to the Start screen and the desktop that they hoped would satisfy critics of the Windows 8 GUIs.

## 计算机代写|操作系统代写operating systems代考|Threats to Computers and Users

What are you risking if your computer or mobile device is not secure? The short answer is that you risk your identity, the work you have created, your company’s integrity, and your own job if you are responsible for loss of the company’s equipment or data. Today, government regulations, such as the Sarbanes-Oxley Act or the Health Insurance Portability and Accountability Act (HIPAA) require that organizations protect certain personal information, such as health and personal financial data. The consequences to an organization that does not comply with these regulations, or that experiences a breach of security involving such data, can be very severe.

A vector is a method that malware uses to infect a computer. While some malware may use just a single vector, multivector malware uses an array of methods to infect computers and networks. Let’s look at a few well-known vectors.

Click Bait. Click bait is content in an email, Web page, social networking page, or within any online app, that is designed to lure you to click on it and its associated link in order to open a Web page or run a video. Click bait may simply be the link itself in an email or a headline or photo containing just enough information to make you curious so that you will click on the link.

Social Networking. Social networking is the use of social media, which is any service (Internet-based or other) that provides a place where people can interact in online communities, sharing information in various forms. Community members generate social-media content. A social networking site is a website that provides space where members can communicate with one another and share details of their business or personal lives. Facebook is a very popular social networking site. Linkedin is a social media site targeted to professionals who use it for business contacts. Twitter (Figure 2-1) allows users to send and receive short text messages (tweets) of up to 140 characters.

## 计算机代写|操作系统代写操作系统代考|今天的桌面操作系统

Windows 7于2009年10月发布，包含了一些改进，纠正了Windows Vista未能被广泛接受的缺点。Windows 7在许多方面都比Windows Vista快，从启动、进入和退出睡眠模式，到连接新设备时识别它们。Windows 7有许多新功能。短列表包括一个重新设计的桌面(见图1-11)，它有一个新的任务栏，它有许多自己的新功能，如跳转列表。关于Windows 7的更多信息，请参见第4章

Windows 8于2012年10月发布，具有更好的安全性和改进的无线连接，并支持一些更新的硬件，如USB $3.0$端口，改进的触摸屏支持同时多重触摸和手势

Windows 8最有争议的变化是GUI，或者更确切地说是GUI。默认的GUI，如图1-12所示，以“开始”屏幕为中心，与Windows 7桌面的三维外观不同。这个新的GUI中的对象看起来是平面的，没有阴影和边框，因此它们不会占用额外的屏幕空间。这是必要的，因为Windows 8可以在各种计算设备上运行:个人电脑、笔记本电脑和平板电脑。Windows 8的开始界面包含了代表应用程序的磁贴。每个贴图可以显示活动内容，如新闻提要，股票报价，幻灯片，和更多，这取决于贴图的应用程序

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

## 计算机代写|操作系统代写operating systems代考|CS401

statistics-lab™ 为您的留学生涯保驾护航 在代写操作系统operating systems方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写操作系统operating systems代写方面经验极为丰富，各种代写操作系统operating systems相关的作业也就用不着说。

• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 计算机代写|操作系统代写operating systems代考|UNIX—The Operating System for All Platforms

UNIX has a longer history than the other operating systems described in this book, and it is still in use today. In fact, Apple’s Mac macOS is a certified UNIX operating system. UNIX grew out of an operating system developed for an early Digital Equipment Corporation (DEC) computer and went through several generations of changes before it emerged from the Bell Labs Computing Science Research Center (Bell Labs) as UNIX version 6 in 1975, a portable operating system for minicomputers and mainframe computers. A portable operating system is one that you can use on a variety of computer system platforms, with only minor alterations required to be compatible with the underlying architecture. Minicomputers and mainframe computers allowed multiple remote users to connect and use the computer’s resources, and UNIX supported the time-sharing and multitasking features that made this possible.

The University of California at Berkeley licensed UNIX, modified it, and distributed it to other schools as Berkeley Software Distribution (BSD) version 4.2. Later versions followed. The schools paid licensing fees to Bell Labs. Students and others improved on and added to UNIX, freely sharing their code with each other. This tradition still prevails today with such versions of UNIX as FreeBSD, NetBSD, OpenBSD, and OpenSolaris. Commercial versions of UNIX today include AIX, OpenServer (derived from SCO UNIX), and HP/UX.

Today UNIX is still used on very large computer systems (referred to as mainframes) and less commonly on Intel desktop systems, as well as on a variety of midsize computers. Versions of UNIX run on many of the world’s Internet servers. Most versions of UNIX also page 12 offer several different user interfaces. Some use character mode, like the traditional shells, such as the Boume shell and the C shell. Others use a graphical interface such as GNOME or KDE. As mentioned earlier, Apple’s macOS operating system is based on a version of UNIX, and it has a graphical user interface.

## 计算机代写|操作系统代写operating systems代考|The Evolution of Desktop Operating Systems

The miniaturization of computer components inevitably led to the evolution of desktop operating systems available to consumers.

Operating systems evolved through many small steps over several decades, some in the form of technical advances and others in evolutionary changes in how people used computers, especially as they saw the need to use computers as multipurpose devices. The “user,” at first a government agency, research institute, or large business, would define the computer’s purpose at any given time by the program chosen to run. In the 1950 s, some early “operating systems” managed data storage on tape for mainframe computers, but it was much more common for application programmers to write system I/O routines (the stuff of today’s OSs) right into their programs. By the mid- 1960 s, as disk systems became more common on large computers, we needed operating systems to manage these disks and to perform other common system-level routines.

The computer enthusiasts who bought the earliest microcomputers of the 1970s, such as the MITS Altair 8800, were infatuated with the technology. What we now consider slow CPU speeds, very limited memory, clumsy I/O devices, and lack of software was exciting and new technology at discussions, and then gather in self-help groups and form clubs such as the Home Brew Computer Club in California’s Silicon Valley. They shared their techniques for creating hardware and programming language software for these computers. Almost every one of these early microcomputers exceeded the expectations of their makers and users, but before long, and for a variety of reasons, most of the early entrepreneurial companies and their products disappeared.

In 1976, Steve Jobs and Stephen Wozniak-two friends working out of a garage-founded Apple Computer, based on their first computer, the Apple I. Their real notoriety began in 1977 when they introduced the Apple II at the West Coast Computer Faire in San Francisco. This created interest in the brand, and the addition of disk drives in 1978 made it a sought-after product for the technically adventurous consumer. The OS for the Apple II did not have a GUI interface-which first appeared in later Apple computers.

The Killer App for the Apple II For a microcomputer to truly become a successful, widely accepted product-used in businesses as well as by hobbyists-it had to be a tool that performed an important task; it had to have an application that many people needed enough to purchase a computer. We call that application a killer app.

One such killer app was VisiCalc, an electronic spreadsheet program introduced in 1979 for the Apple II computer (running the Apple OS). Before microcomputers and programs like VisiCalc, people created spreadsheets manually, on large grid-printed sheets of paper. Consider one scenario: the manager of a small retail store would enter a column of numbers-say, sales for one product in the store-day-by-day for a month. Then he would add up the daily columns to get the total sales for that product for that month. The next column was for the next product, and so on. The process was tedious and error prone, but very valuable to the manager of the store. VisiCalc automated this thankless job, remembered the formulas for the calculations, and allowed people to $\frac{\text { page } 14}{}$ recalculate a whole column of numbers after changes were made.

## 计算机代写|操作系统代写operating systems代考| UNIX-The operating System for All platform

.操作系统

UNIX的历史比本书中描述的其他操作系统要长，直到今天仍在使用。事实上，苹果的Mac macOS是经过认证的UNIX操作系统。UNIX起源于一个为早期数字设备公司(DEC)计算机开发的操作系统，经过几代人的变化，才在1975年从贝尔实验室(Bell Labs)计算科学研究中心(Bell Labs)出现为UNIX版本6，这是一种适用于小型计算机和大型计算机的便携式操作系统。可移植操作系统是一种可以在各种计算机系统平台上使用的操作系统，只需要进行微小的修改就可以与底层体系结构兼容。小型计算机和大型计算机允许多个远程用户连接和使用计算机的资源，而UNIX支持分时和多任务处理功能，使这成为可能

## 计算机代写|操作系统代写operating systems代考|桌面操作系统的进化

. The Evolution of Desktop operating systems . The

1976年，史蒂夫·乔布斯和斯蒂芬·沃兹尼亚克——这两个朋友在一家车库建立的苹果电脑公司工作，他们的第一台电脑是Apple i。1977年，他们在旧金山的西海岸计算机博览会上推出Apple II，真正声名狼藉。这引起了人们对该品牌的兴趣，并且在1978年增加了磁盘驱动器，使它成为技术冒险型消费者的抢手产品。Apple II的操作系统没有GUI界面，而GUI界面最早出现在后来的Apple电脑上

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。