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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!-- but may not be published or retransmitted without explicit permission.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 21:47:46 2005 by faqproc version 2.7 --><!-- from source file stdio.sgml dated Wed Dec 21 13:07:57 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/stdio/textvsbinary.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:58 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 12.40</title><link href="stdinbinary.html" rev=precedes><link href="structio.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="stdinbinary.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="structio.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 12.40</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>What's the difference between text and binary I/O?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>In text mode,a file is assumed to consist oflines of printable characters(perhaps including tabs).The routines in the stdio library(<TT>getc</TT>, <TT>putc</TT>, and all the rest)translate betweenthe underlying system'send-of-line representationand the single <TT>\n</TT> used in C programs.C programswhich simply read and write texttherefore don't have to worry aboutthe underlying system'snewline conventions:when a C program writes a <TT>'\n'</TT>,the stdio librarywritesthe appropriate end-of-line indication,and when the stdio library detectsan end-of-line while reading,it returns a single <TT>'\n'</TT>to the calling program.<a href="recfs.html" rel=subdocument>[footnote]</a></p><p>In binary mode, on the other hand,bytes are read and written between the program and the file without any interpretation.(On MS-DOS systems,binary mode also turns offtesting for control-Zas an in-bandend-of-file character.)</p><p>Text mode translationsalsoaffect the apparent size of a file as it's read.Because the charactersread from and written toa file in text modedo not necessarily matchthe charactersstored in the file exactly,thesize of the file on diskmay not always matchthe number of characters which can be read from it.Furthermore,for analogous reasons,the <TT>fseek</TT> and<TT>ftell</TT> functionsdo notnecessarilydeal in pure byte offsets from the beginning of the file.(Strictly speaking,in text mode,the offset values used by <TT>fseek</TT> and <TT>ftell</TT>should not be interpreted at all:a value returned by <TT>ftell</TT>should only be used as a later argument to <TT>fseek</TT>,and <em>only</em> values returned by <TT>ftell</TT>should be used as arguments to <TT>fseek</TT>.)</p><p>In binary mode,<TT>fseek</TT> and <TT>ftell</TT> do use pure byte offsets.However,some systems may have to appenda number ofnull bytes at the endof a binary fileto pad it out toa full record.</p><p>See also questions <a href="binaryio.html">12.37</a> and <a href="../osdep/filesize.html">19.12</a>.</p><p>References:ISO Sec. 7.9.2<br>Rationale Sec. 4.9.2<br>H&S Sec. 15 p. 344, Sec. 15.2.1 p. 348<br></p><!-- aend --><p><hr><a href="stdinbinary.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="structio.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/stdio/textvsbinary.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:58 GMT --></html>⌨️ 快捷键说明
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