Application（应用程序）

应用程序是用于向用户提供功能的软件。从终端用户使用的字处理和阅读邮件功能，到服务器端的数据库和网页服务都属于功能的范畴。

Bug

软件中导致程序工作不正常或不能满足要求的错误。现代软件中的错误常常是由程序员引入的，而且几乎所有的大型软件系统都有这类错误。

FTP（文件传输协议）

文件传输协议（File Transfer Protocol, FTP）是用于传送文本和数据文件的协议。这个协议标准可以追溯到因特网的早期，目前仍然是计算机系统之间传送数据的最常用的方法之一。

HTML（超文本标记语言）

超文本标记语言（HyperText Markup Language, HTML）是万维网上所有页面的编码语言。HTML 包括数据和在浏览器中以正确的格式显示这些数据的指令，也包含着存取相关数据的指令。

HTTP（超文本传输协议）

超文本传输协议（HyperText Transfer Protocol, HTTP）是一种控制不同计算机之间数据传输的协议。HTTP 是浏览器和网页服务器之间最常用的传输方式，但也用来传输其他类型的数据。该协议也支持加密和压缩。

LAN（局域网）

局域网（Local Area Network, LAN）一般是指覆盖像办公楼或住宅这样的较小的地理区域的计算机网络。局域网可以连接到因特网，也可以是不与外界通信的独立的网络。一般的局域网用途包括让不同的计算机共享打印机和数据资源。

Operating System（操作系统）

操作系统（OS）是计算机上一系列控制硬件（磁盘驱动器，显示部分，键盘，鼠标，等等）的软件和其他应用程序。OS 为其下运行的各种程序管理和分配物理资源（CPU 处理时间，硬盘空间，键盘输入，等等）。OS 只提供最低限度的用户功能。用户功能通常由应用程序提供，而 OS 是硬件和应用程序之间的中间层。微软 Windows，GNU/Linux，升阳 Solaris 和 Mac OS X 都是操作系统的例子。

Proprietary Software（私有软件）

一般指由商业公司开发，并对用户有严格的授权要求的软件。使用未经 FSF 和／或 OSI 认证的授权发布的软件在本书中都看作是私有软件。大部分私有软件不允许用户自行分发，也不提供源代码，虽然也有例外。公共领域中的软件不被看作私有软件。

Public Domain Software（公共领域软件）

不专属于某人，所有人都能不受限制任意获取的软件。

Source Code（源代码）

源代码指构成从 Linux 或微软 Windows 这样的操作系统，到 Oracle，MS SQL Server 和 Photoshop 这样的应用软件的所有程序核心的指令，以人们可以读懂的方式写成。虽然读懂源代码对一般人并不容易，但软件工程师通过源代码可以轻易地理解、修正和改动程序。例如，一段代码可以是这样[96]：


Float distance (p0, p1)
struct point p0, p1;
{
float xdist = p1.x - p0.x;
float ydist = p1.y - p0.y;
return sqrt (xdist * xdist + ydist * ydist);
}


软件工程师完成源代码的编写后，它被转换为下面这样的机器能够读取的形式：


1314258944 -232267772 -231844864 1634862
1314258944 -232267772 -231844864 1634862
1411907592 -231844736 2159150 1420296208
1411907592 -231844736 2159150 1420296208
-234880989 -234879837 -234879966 -232295424
1644167167 -3214848 1090581031 1962942495
572518958 -803143692 1314803317


如果程序被转换成机器可以读取的格式，就几乎没有工程师能读懂，更不用说修改。因此，大部分私有软件都是只以机器可读的格式传播，它们的源代码被作为最重要的机密保存。

TCP/IP（因特网协议上的传输控制协议）

因特网协议上的传输控制协议（Transmission Control Protocol, TCP/IP）是今天因特网和以太网局域网大部分应用背后的协议。TCP/IP 是由美国 DARPA 开发的，它在底层提供了一种可靠的通信机制。许多因特网协议（HTTP，FTP，telnet）都是在 TCP/IP 协议的基础上构建的。

瘦客户机

在瘦客户机架构中，大部分计算和数据存储的任务都是在强力的服务器上完成的。用户桌面上的系统功能较弱，只显示服务器返回的数据。今天运行微软 Windows 的标准桌面系统是“胖”客户机系统，负责运行大部分的处理和数据存储工作，服务器只负责少量的工作。

使用瘦客户机架构有很多优势，特别是较低的硬件费用和运行成本。因为所有数据和应用程序都存储在服务器上，管理员可以方便地管理和更新系统。主服务器上的改动将立即在所有用户系统上生效。极低的数据存储和处理需求也使得便宜的桌面系统不需要像今天的胖客户机桌面系统那样经常升级。

Application
Applications are software written to supply functionality to the user. Functionality can range from end-user functions such as word processing and email reading, to server functions like databases and web servers.

Bug
An error in software that causes the program to malfunction, fail or not meet specifications. Modern bugs are usually introduced by programmer error and almost all major applications have some bugs in the system.

FTP
File Transfer Protocol – the protocol used to transfer files, both text and data. The standard dates back to the early years of the Internet and is still one of the more commonly used methods for transferring data between computer systems.

HTML
HyperText Markup Language – the language in which all web pages on the World Wide Web are encoded. HTML contains both data and instructions on how to format the data properly in a web browser. It also contains instructions on accessing related data.

HTTP
HyperText Transfer Protocol – a protocol for controlling the transfer of data between different machines. HTTP is the most commonly used transfer method between web servers and web browsers, although it has been used to transfer other types of data and traffic. It has support for encryption and compression.

LAN
Local Area Network – a data network of computers, typically covering a small geographic region, such as an office building or house. A LAN may be connected to the Internet or be a separate, distinct network that communicates only within itself. Common uses for LANs include sharing printing resources and data between computers.

Operating System
The Operating System (OS) is the collection of software that controls the hardware (disk drives, displays, keyboard, mouse, etc.) and software applications on a computer. The OS manages and allocates the physical resources (CPU processing time, hard disk space, inputs from the keyboard, etc.) among the different applications that run within it. The OS supplies minimal user functionality. User functionality is typically supplied by applications, while the OS serves as an intermediary between hardware and application. Examples of an OS are Microsoft Windows, GNU/Linux, Sun Microsystem’s Solaris and Mac OS X.

Proprietary Software
Typically refers to software produced by commercial companies and licensed to users under very restrictive licenses. Any software released under licenses other than the FSF and/or OSI approved licenses are considered proprietary software for the purpose of this primer. Most proprietary software typically cannot be redistributed by the user; nor is access provided to the source code, though there are exceptions. Public domain software is not considered proprietary software.

Public Domain Software
Software that is not owned by anyone and is available to all, with no restrictions.

Source Code
Source code represents the human readable instructions that form the heart of any program, be they operating systems such as Linux or Microsoft Windows, or accounting, database and graphical applications such as Oracle, MS SQL Server and Photoshop. Although it is not easily readable to lay people, software engineers can easily understand, correct and modify programs using the original source code. For example, a portion of code may look like thisi:

Float distance (p0, p1)
struct point p0, p1;
{
float xdist = p1.x - p0.x;
float ydist = p1.y - p0.y;
return sqrt (xdist * xdist + ydist * ydist);
}

Once software engineers are finished with source code, it is converted to machine-readable code that looks like this:

1314258944 -232267772 -231844864 1634862
1411907592 -231844736 2159150 1420296208
-234880989 -234879837 -234879966 -232295424
1644167167 -3214848 1090581031 1962942495
572518958 -803143692 1314803317

Few engineers are able to understand, much less modify, a program once it has been converted to a machine-readable format. Because of this, most proprietary software is distributed in machine-readable form only and the source code is a jealously guarded secret.

TCP/IP
Transmission Control Protocol over Internet Protocol – the protocol that underlies most of the Internet today, as well as most Ethernet LANs. TCP/IP was developed by the US agency DARPA. It supplies a reliable communication protocol at a very low level. Most Internet protocols (HTTP, FTP, telnet) are built on top of the TCP/IP protocol.

Thin Client
A thin-client infrastructure is one where most of the computational and data storage tasks are done on powerful server systems. The end-user system sitting on desktops are low-powered, displaying only the data returned by the servers. Standard desktop systems today running Microsoft Windows are fat-client systems, where most of the processing and data storage work is done by the desktop system and only a limited amount of work is done by the server.

Various advantages can be gained from using a thin-client infrastructure, mostly centering around lower maintenance and hardware costs. Because all data is stored on the server, including the applications, it is easier for administrators to manage and update the systems. A single change on the main server will immediately be reflected on all user systems. Likewise, the minimal data storage and processing requirements result in cheap desktop systems that do not need to be updated as regularly as today's fat-client desktops.