📄 toupper.html
字号:
<!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!-- but may not be published or retransmitted without explicit permission.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 lib1.sgml dated Sat Feb 7 18:46:53 2004 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/lib/toupper.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 13.5</title><link href="strupper.html" rev=precedes><link href="strtok.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="strupper.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="strtok.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 13.5</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>Whydo some versions of<TT>toupper</TT> act strangely if given an upper-case letter?<br>Why does some code call <TT>islower</TT> before <TT>toupper</TT>?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>In earlier times,<TT>toupper</TT>was afunction-likepreprocessor macroandwas defined to work only onlower-case letters;itmisbehavedif applied to digits, punctuation,or letters which were already upper-case.Similarly,<TT>tolower</TT>worked only on upper-case letters.Therefore,old code(or code writtenfor wide portability)tends to call<TT>islower</TT> before <TT>toupper</TT>,and<TT>isupper</TT> before <TT>tolower</TT>.</p><p>The C Standard, however,says that <TT>toupper</TT> and <TT>tolower</TT>must work correctly on all characters,i.e. characterswhich don't need changingareleftalone.</p><p>References:ISO Sec. 7.3.2<br>H&S Sec. 12.9 pp. 320-1<br>PCS p. 182<br></p><!-- aend --><p><hr><a href="strupper.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="strtok.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/lib/toupper.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:58 GMT --></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -