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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>Portability Considerations (Informative)</title></head><body bgcolor="white"><basefont size="3"> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h2><a name="tag_04"></a>Portability Considerations (Informative)</h2><p>This section contains information to satisfy various international requirements:</p><ul><li><p><a href="#tag_04_01">User Requirements</a> describes perceived user requirements.</p></li><li><p><a href="#tag_04_02">Portability Capabilities</a> indicates how the facilities of IEEE Std 1003.1-2001 satisfy thoserequirements.</p></li><li><p><a href="#tag_04_03">Profiling Considerations</a> offers guidance to writers of profiles on how the configurable options,limits, and optional behavior of IEEE Std 1003.1-2001 should be cited in profiles.</p></li></ul><h3><a name="tag_04_01"></a>User Requirements</h3><p>This section describes the user requirements that were perceived by the developers of IEEE Std 1003.1-2001. Theprimary source for these requirements was an analysis of historical practice in widespread use, as typified by the base documentslisted in <a href="xbd_chap01.html#tag_01_01_01"><i>Scope</i></a> .</p><p>IEEE Std 1003.1-2001 addresses the needs of users requiring open systems solutions for source code portability ofapplications. It currently addresses users requiring open systems solutions for source-code portability of applications involvingmulti-programming and process management (creating processes, signaling, and so on); access to files and directories in a hierarchyof file systems (opening, reading, writing, deleting files, and so on); access to asynchronous communications ports and otherspecial devices; access to information about other users of the system; facilities supporting applications requiring bounded(realtime) response.</p><p>The following users are identified for IEEE Std 1003.1-2001:</p><ul><li><p>Those employing applications written in high-level languages, such as C, Ada, or FORTRAN.</p></li><li><p>Users who desire conforming applications that do not necessarily require the characteristics of high-level languages (forexample, the speed of execution of compiled languages or the relative security of source code intellectual property inherent in thecompilation process).</p></li><li><p>Users who desire conforming applications that can be developed quickly and can be modified readily without the use of compilersand other system components that may be unavailable on small systems or those without special application developmentcapabilities.</p></li><li><p>Users who interact with a system to achieve general-purpose time-sharing capabilities common to most business or governmentoffices or academic environments: editing, filing, inter-user communications, printing, and so on.</p></li><li><p>Users who develop applications for POSIX-conformant systems.</p></li><li><p>Users who develop applications for UNIX systems.</p></li></ul><p>An acknowledged restriction on applicable users is that they are limited to the group of individuals who are familiar with thestyle of interaction characteristic of historically-derived systems based on one of the UNIX operating systems (as opposed to otherhistorical systems with different models, such as MS/DOS, Macintosh, VMS, MVS, and so on). Typical users would include programdevelopers, engineers, or general-purpose time-sharing users.</p><p>The requirements of users of IEEE Std 1003.1-2001 can be summarized as a single goal: <i>application sourceportability</i>. The requirements of the user are stated in terms of the requirements of portability of applications. This in turnbecomes a requirement for a standardized set of syntax and semantics for operations commonly found on many operating systems.</p><p>The following sections list the perceived requirements for application portability.</p><h4><a name="tag_04_01_01"></a>Configuration Interrogation</h4><p>An application must be able to determine whether and how certain optional features are provided and to identify the system uponwhich it is running, so that it may appropriately adapt to its environment.</p><p>Applications must have sufficient information to adapt to varying behaviors of the system.</p><h4><a name="tag_04_01_02"></a>Process Management</h4><p>An application must be able to manage itself, either as a single process or as multiple processes. Applications must be able tomanage other processes when appropriate.</p><p>Applications must be able to identify, control, create, and delete processes, and there must be communication of informationbetween processes and to and from the system.</p><p>Applications must be able to use multiple flows of control with a process (threads) and synchronize operations between theseflows of control.</p><h4><a name="tag_04_01_03"></a>Access to Data</h4><p>Applications must be able to operate on the data stored on the system, access it, and transmit it to other applications.Information must have protection from unauthorized or accidental access or modification.</p><h4><a name="tag_04_01_04"></a>Access to the Environment</h4><p>Applications must be able to access the external environment to communicate their input and results.</p><h4><a name="tag_04_01_05"></a>Access to Determinism and Performance Enhancements</h4><p>Applications must have sufficient control of resource allocation to ensure the timeliness of interactions with externalobjects.</p><h4><a name="tag_04_01_06"></a>Operating System-Dependent Profile</h4><p>The capabilities of the operating system may make certain optional characteristics of the base language in effect no longeroptional, and this should be specified.</p><h4><a name="tag_04_01_07"></a>I/O Interaction</h4><p>The interaction between the C language I/O subsystem ( <i>stdio</i>) and the I/O subsystem of IEEE Std 1003.1-2001must be specified.</p><h4><a name="tag_04_01_08"></a>Internationalization Interaction</h4><p>The effects of the environment of IEEE Std 1003.1-2001 on the internationalization facilities of the C language mustbe specified.</p><h4><a name="tag_04_01_09"></a>C-Language Extensions</h4><p>Certain functions in the C language must be extended to support the additional capabilities provided byIEEE Std 1003.1-2001.</p><h4><a name="tag_04_01_10"></a>Command Language</h4><p>Users should be able to define procedures that combine simple tools and/or applications into higher-level components thatperform to the specific needs of the user. The user should be able to store, recall, use, and modify these procedures. Theseprocedures should employ a powerful command language that is used for recurring tasks in conforming applications (scripts) in thesame way that it is used interactively to accomplish one-time tasks. The language and the utilities that it uses must be consistentbetween systems to reduce errors and retraining.</p><h4><a name="tag_04_01_11"></a>Interactive Facilities</h4><p>Use the system to accomplish individual tasks at an interactive terminal. The interface should be consistent, intuitive, andoffer usability enhancements to increase the productivity of terminal users, reduce errors, and minimize retraining costs. Onlinedocumentation or usage assistance should be available.</p><h4><a name="tag_04_01_12"></a>Accomplish Multiple Tasks Simultaneously</h4><p>Access applications and interactive facilities from a single terminal without requiring serial execution: switch betweenmultiple interactive tasks; schedule one-time or periodic background work; display the status of all work in progress or scheduled;influence the priority scheduling of work, when authorized.</p><h4><a name="tag_04_01_13"></a>Complex Data Manipulation</h4><p>Manipulate data in files in complex ways: sort, merge, compare, translate, edit, format, pattern match, select subsets (strings,columns, fields, rows, and so on). These facilities should be available to both conforming applications and interactive users.</p><h4><a name="tag_04_01_14"></a>File Hierarchy Manipulation</h4><p>Create, delete, move/rename, copy, backup/archive, and display files and directories. These facilities should be available toboth conforming applications and interactive users.</p><h4><a name="tag_04_01_15"></a>Locale Configuration</h4><p>Customize applications and interactive sessions for the cultural and language conventions of the user. Employ a wide variety ofstandard character encodings. These facilities should be available to both conforming applications and interactive users.</p><h4><a name="tag_04_01_16"></a>Inter-User Communication</h4><p>Send messages or transfer files to other users on the same system or other systems on a network. These facilities should beavailable to both conforming applications and interactive users.</p><h4><a name="tag_04_01_17"></a>System Environment</h4><p>Display information about the status of the system (activities of users and their interactive and background work, file systemutilization, system time, configuration, and presence of optional facilities) and the environment of the user (terminalcharacteristics, and so on). Inform the system operator/administrator of problems. Control access to user files and otherresources.</p><h4><a name="tag_04_01_18"></a>Printing</h4><p>Output files on a variety of output device classes, accessing devices on local or network-connected systems. Control (orinfluence) the formatting, priority scheduling, and output distribution of work. These facilities should be available to bothconforming applications and interactive users.</p><h4><a name="tag_04_01_19"></a>Software Development</h4><p>Develop (create and manage source files, compile/interpret, debug) portable open systems applications and package them fordistribution to, and updating of, other systems.</p><h3><a name="tag_04_02"></a>Portability Capabilities</h3><p>This section describes the significant portability capabilities of IEEE Std 1003.1-2001 and indicates how the userrequirements listed in <a href="#tag_04_01">User Requirements</a> are addressed. The capabilities are listed in the same format asthe preceding user requirements; they are summarized below:</p><ul><li><p>Configuration Interrogation</p></li><li><p>Process Management</p></li><li><p>Access to Data</p></li><li><p>Access to the Environment</p></li><li><p>Access to Determinism and Performance Enhancements</p></li><li><p>Operating System-Dependent Profile</p></li><li><p>I/O Interaction</p></li><li><p>Internationalization Interaction</p></li><li><p>C-Language Extensions</p></li><li><p>Command Language</p></li><li><p>Interactive Facilities</p></li><li><p>Accomplish Multiple Tasks Simultaneously</p></li>⌨️ 快捷键说明
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