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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:47 2005 by faqproc version 2.7 --><!-- from source file osdepmisc.sgml dated Wed Dec 21 13:04:19 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/osdep/sysdep.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:04 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 19.42</title><link href="gottabe.html" rev=precedes><link href="../misc/multretval.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="gottabe.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="../misc/multretval.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 19.42</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Whyisn't any of thisstandardized in C?Any real program has to do some of these things.</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>Actually,some standardization has occurred along the way.In the beginning,C did not have a standard library at all;programmers always had to ``roll their own'' utilityroutines.After several abortive attempts,acertainsetof library routines(including the <TT>str*</TT>and stdio families of routines)became a <I>de facto</I> standard,at least on Unix systems,but the library was notyeta formal part of the language.Vendors could(and occasionally did)provide completely different routines along with their compilers.</p><p>In ANSI/ISO Standard C,a library definition(based onthe 1984 /usr/group standard,andlargely compatible withthe traditional Unix library)was adopted with as much standing as the language itself.The Standard C library's treatment of file and device I/O is,however,ratherminimal.It states how streams of characters are written to and read from files,and it provides a few suggestionsabout thedisplaybehavior ofcontrol characters like <TT>\b</TT>, <TT>\r</TT>, and <TT>\t</TT>,but beyond that it is silent.(Many of these issues are, however,addressed and standardized in Posix.)</p><p>If the Standard weretoattempt to define standard mechanisms for accessingthings likekeyboards and displays,itmight seem to be a big convenience for programmers.But it would be a monumentaltask:there is already a huge variety of display devices,and huge variation among the operating systems through which theyare usually accessed.We cannot assume that the years to come will offer any less variety.</p><p>At one time the common output device for C programs was a Teletype;later it was a``dumb'' terminal,after that it was a ``smart'' VT100 or other ANSI X3.64-compatible terminalwhich today might be called ``dumb.''Todayit's likely to be a bitmapped color display screen.What will it be in five years?How will the operating systems of that time deal with its capabilities?</p><p>See also question <a href="../ansi/appalled.html">11.34</a>.</p><p>References:Rationale Sec. 2.2.2, Sec. 4.9, Sec. 4.9.2<br></p><!-- aend --><p><hr><a href="gottabe.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="../misc/multretval.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/osdep/sysdep.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:59:04 GMT --></html>⌨️ 快捷键说明
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