锘??xml version="1.0" encoding="utf-8" standalone="yes"?>
char *pStr;
char ch;
char str[] = "Hello";
ch = str[1];
*pStr = str[1];
printf("ch = %c\n", ch);
printf("*pStr = %c", *pStr);
姝ゆ椂鎵撳嵃ch鍊肩殑鏃跺欒兘姝g‘杈撳嚭錛屼絾鏄墦鍗皃Str[0]鐨勬椂鍊欏氨鍑洪棶棰樹簡(jiǎn)錛岃窡韙彂鐜版槸pStr[0] = str[1];榪欏彞鍑虹幇闂銆?BR>
鍘熸潵錛宑har *pStr; 鍙畾涔変簡(jiǎn)涓涓?瀛楄妭鐨勬寚閽堝彉閲忥紝鑰岃繖涓彉閲忛噷闈㈢殑鍐呭鏄皢瑕佹寚鍚戜竴涓猚har綾誨瀷鍙橀噺鐨勶紝浣嗘槸姝ゆ椂pStr鍙槸涓滈噹鎸囬拡鈥濓紝騫舵病鏈夋寚鍚戜竴涓猚har綾誨瀷鐨勫唴瀛樺崟鍏冿紝鎵浠ワ紝褰撶敤*pStr鏉ヨ闂繖涓厓绱犳椂錛岀郴緇熸牴鏈笉鐭ラ亾璇ヨ闂綍澶勭殑絀洪棿錛屽洜姝わ紝鍦ㄤ嬌鐢╬Str鍓嶏紝蹇呴』璁╁畠鎸囧悜涓涓叿浣撶殑絀洪棿銆?BR>
鐢變笂闈㈠彲浠ュ皢鐩稿叧璇彞鏀逛負(fù)
char *pStr;
char ch;
char str[] = "Hello";
pStr = &ch; //pStr鎸囧悜ch銆佽幏寰楀垵濮嬪寲
pStr = &str[1]; //pStr鎸囧悜str[1]鍦板潃銆佽幏寰楀垵濮嬪寲
ch = str[1];
*pStr = str[1];
printf("ch = %c\n", ch);
printf("*pStr = %c", *pStr);
鈼庡彟澶栵紝鍦ㄥ瓙鍑芥暟涓嬌鐢╩alloc()/new()鍒嗛厤鐨勫唴瀛樼┖闂翠笉浼?xì)鍥犲瓙鍑芥暟鐨剺q斿洖鑰屾秷澶?/FONT>錛屽嚱鏁板彧浼?xì)娓呯悊璋冨瓙鍑芥暟閲屽畾涔夌殑鍙橀噺鐨劷I洪棿錛屽錛?
char* func()
{
char *p;
p = (char *)malloc(sizeof(char));
return p;
} //榪斿洖鍚庯紝p鎵鍦ㄧ┖闂磋閲婃斁錛屼絾鏄痯鎵鎸囩┖闂磋繕瀛樺湪
姝や腑鏂規(guī)硶鍙互鐢ㄦ潵瑙e喅鈥滄寚閽堢殑鎸囬拡鈥濅嬌鐢ㄤ笉鏂逛究鐨勯棶棰樸傛楠ゅ垎2姝ワ細(xì)1銆佹妸浼犲叆鐨勬寚閽堢殑鎸囬拡鍙傛暟鍘繪帀錛?銆佹妸鍑芥暟鐨勮繑鍥炲艱祴緇欒鏀瑰彉鐨勫璞$殑鎸囬拡錛?
void GetMemory2(char **p, int num)
{
*p = (char *)malloc(sizeof(char) * num);
}
void Test2(void)
{
char *str = NULL;
GetMemory2(&str, 100); // 娉ㄦ剰鍙傛暟鏄?nbsp;&str錛岃屼笉鏄痵tr
strcpy(str, "hello");
cout<< str << endl;
free(str);
}
/**///////涓嬮潰鏄敤浼犻掑姩鎬佸唴瀛樼殑鏂規(guī)硶瀹炵幇
char *GetMemory3(int num)
{
char *p = (char *)malloc(sizeof(char) * num);
return p;
}
void Test3(void)
{
char *str = NULL;
str = GetMemory3(100);
strcpy(str, "hello");
cout<< str << endl;
free(str);
}
]]>
2銆傛寚閽堝彉閲忔槸鏈夊瓨鍌ㄧ┖闂寸殑錛涜屾暟緇勫悕浠呬粎鏄竴涓爣鍙鳳紝娌℃湁瀹為檯瀛樺偍絀洪棿錛屽崟鍗曚竴涓暟緇勫悕灝卞彧鑳借〃紺鴻鏁扮粍鐨勭1涓厓绱犵殑鍦板潃銆俰nt a[10]; 瑙勫畾&a灝辯瓑浜?amp;a[0]鎴栬卆 .
3銆備緥濡?char str[]= "hello world"鍜宑har *p = "hello world"涓紝鏁扮粍str鏄厛鍒嗛厤緇欎粬鍏冪礌涓暟涓唴瀛橈紝鐒跺悗灝嗗悗闈㈢殑瀛楃涓插鍒剁粰榪欎釜絀洪棿錛堟敞鎰忥紝姝ゆ椂搴旇鑰冭檻\0瀛楃錛夛紱鑰宲鐨勫緩绔嬭繃紼嬫槸鍏堝湪闈?rùn)鎬佸瓨鍌ㄥ尯寤虹珛甯稿瓧絎︿覆"hello world\0"錛岀劧鍚庡皢p鎸囧悜榪欎釜甯稿瓧絎︿覆銆傛墍浠ユ暟緇剆tr涓厓绱犵殑鍐呭鍙互閫氳繃閲嶆柊璧嬪兼敼鍙橈紝鑰宲鎸囧悜鐨勫唴瀹逛笉鑳芥敼鍙樸?img src ="http://www.shnenglu.com/geforcex/aggbug/1863.html" width = "1" height = "1" />
]]>
鏈瘒涓昏鍐欑粰瀵筩onst璇硶鐞嗚В瀛樺湪璇尯鐨刢++瀛︿範(fàn)鑰咃紝甯屾湜鎵鏈夊榪欐柟闈㈡瘮杈冩ā緋婄殑鏈嬪弸鍙互闃呰騫朵粠涓壘鍒頒竴浜涚瓟妗堛?
銆?
2004-11-19 21:00
Const 鏈鏃╂兂娉曟槸鐢ㄤ簬鍙栦唬棰勫鐞嗗櫒#define 榪欎釜瀹忥紝浠庤屽艦鎴?A name=1>甯擱噺鐨勬蹇點(diǎn)傞拡瀵瑰父閲廲onst瀵硅薄錛宑onst鎸囬拡鍙?qiáng)鎸囧悜const鐨勬寚閽堬紝鍑芥暟const綾誨瀷鍙傛暟錛宑onst 鍑芥暟榪斿洖綾誨瀷錛?const綾繪垚鍛橈紝鍙?qiáng)const鎴愬憳鍑芥暟錛屽強(qiáng)瀵筩onst鏈鍚庣悊瑙g殑涓浜涙葷粨鏉ユ弿榪?const銆?
鈶?const瀵硅薄鍜宑onst綾誨瀷鐨勫璞?
瀵逛簬榪欎袱涓蹇電殑鎻忚堪濡備笅
1. int const Object; //Object鏄竴涓猚onst閲忔槸涓嶅彲浠ヨ淇敼 Object = 2;Error
2. const int Object; //Object鏄?const int鍨嬩粬鎵瀛樻斁鐨勫唴瀹逛笉鍙互琚慨鏀?
瀵逛簬1錛?榪欎袱縐峜onst鐢ㄤ簬瀵硅薄錛岃〃榪拌櫧鐒朵笉鍚屼絾鏄晥鏋滄槸涓鏍風(fēng)殑銆傚洜涓哄璞℃湰韜瓨鏀劇潃鍐呭瀵瑰璞$殑鏀瑰彉灝辨槸瀵逛簬瀵硅薄鍐呭鐨勬敼鍙橈紝鍚屾牱鏀瑰彉鍚庤呬篃鏄湪鏀瑰彉鍓嶈呫傛墍浠ヨ涔変笂涓鏍風(fēng)殑銆?
鈶?const鎸囬拡 鍜?鎸囧悜const鐨勬寚閽?鍙?qiáng)涓よ呯粨鍚?
瀵逛簬涓変釜姒傚康鎻忚堪濡備笅
1. int* const p; //鎸囬拡p鏄痗onst涓嶈兘琚慨鏀?渚嬪p++; //淇敼p鏈韓浼?xì)Error
//淇敼p鎸囧悜鍐呭 *p = 2; //OK
2. const int* p; //p鏄寚鍚戜竴涓暣褰㈠父閲忕殑鎸囬拡鎸囧悜鐨勫唴瀹逛笉鍙互鏀瑰彉 p++;//OK
// *p = 2; //Error
3. const int* const p; //鎸囬拡p鏈韓鏄笉鑳借淇敼騫朵笖p鎵鏈夋湁鏁堢殑鍐呭涔熶笉鑳借
//淇敼 *p = 2; Error 鍜?p++; Error
鈶?const 鍙傛暟淇グ 鍜?鍙傛暟榪斿洖綾誨瀷鐨刢onst淇グ
1.const 鍙傛暟淇グ
姝ゆ椂鍑芥暟鍙傛暟淇グ const鐨勫叿浣撶敤娉?鈶?鈶′腑鐢ㄦ硶鏄竴鏍風(fēng)殑
渚嬪 void Fun( const int I ) { I++;} //Error涓嶈兘淇敼甯擱噺I
2.const淇グ鍑芥暟榪斿洖綾誨瀷鐢ㄦ硶涔熸槸綾諱技浜?鈶犫憽涓?浠呬粎淇グ鐨勫璞″彉鍖栧彉鎴愪竴涓繑鍥炲璞?
渚嬪錛歝onst int Fun() { static int I; return I;}
int Res = (Fun())++ //Error涓嶈兘淇敼甯擱噺榪斿洖瀵硅薄
鈶?const綾繪垚鍛?鍜?const 鎴愬憳鍑芥暟
1. const鎴愬憳
綾籧onst鎴愬憳鍦ㄦ瀯閫犳湡闂翠細(xì)鍏佽琚垵濮嬪寲騫朵笖鍦ㄤ互鍚庝笉鑳借鏀瑰彉銆傛垜浠氨鍙互鐭ラ亾綾籧onst鎴愬憳鍜屼竴鑸琧onst 鍙橀噺鏄湁鎵涓嶅悓鐨勶紝綾籧onst鎴愬憳鏄搴斾簬姣忎釜瀵硅薄鑰岃█鎵嶆湁鎰忎箟銆傚洜涓轟粬鍦ㄦ瀯閫犳湡琚垵濮嬪寲錛屽彧鏈夊綋綾誨疄渚嬪寲鍚庢墠浼?xì)杩涜鏋勯犮傛墍浠ョ被const鎴愬憳鍙互榪欐牱鎻忚堪: 鍦ㄧ被鐨勬瘡涓嬈″疄渚嬪寲鏃惰鍒濆鍖栵紝鍦ㄨ繖涓璞$殑鐢熷瓨鍛ㄦ湡涓笉鍙敼鍙樸?
2. const 鎴愬憳鍑芥暟
鎻忚堪: void Class::MemberFun() const {}; //姝ゆ椂榪欎釜const淇グ鐨則his鎵鏈夌被鎴愬憳鍙橀噺閮戒笉鍏佽鍦ㄨ繖涓嚱鏁頒綋浣滅敤鍚庤淇敼銆傝繖鍦ㄨ璁′笂浼?xì)甯︽潵涓浜涘ソ澶勶紝鑳介槻姝綘鎰忓鐨勫鐞嗗甫鏉ョ殑闂銆?
鎬葷粨:
<1> const 甯擱噺 涓鑸紪璇戝櫒涓嶄細(xì)鍒嗛厤絀洪棿鍙槸緇存姢涓寮犺〃銆傝屽綋extern 澶栭儴寮曠敤榪欎釜甯擱噺鎴栬呪?amp;鈥濆榪欎釜甯擱噺鍙栧湴鍧鏃訛紝緙栬瘧鍣ㄦ墠浼?xì)湄?fù)鍏跺垎閰嶅湴鍧銆侰onst鏈韓鐨勬満鍒舵瘮杈冨鏉傘?
<2> const 璁板繂娉曞垯 const淇グ鍚庨潰涓涓渶榪戠殑鍚嶇О銆傛垜鏇懼垵瀛︾殑鏃跺欒const 淇グ鎼炵殑緋婇噷緋婃秱錛屽悗鏉ユ參鎱㈢殑鎬葷粨鎴戣寰楄繖鏍風(fēng)悊瑙f渶瀹規(guī)槗鐨勩?
渚嬪瓙: const int I; 姝ゆ椂const浠呬粎淇グint 琛ㄦ槑 I涓嶆槸涓涓父閲忎絾鏄疘鐨勫唴瀹規(guī)槸甯擱噺銆傚洜涓篶/c++琛ㄨ揪 瀵笽鐨勬敼鍙樺氨鏄I鍐呭鐨勬敼鍙樻墍浠?I涔熺被浼間竴涓猚onst銆傚ぇ瀹朵笉濡ㄥ彲浠ョ敤鎸囬拡const淇グ璇曡瘯鐞嗚В浼?xì)鏈夊府鍔╃殑鎴戞儫雬?
<3> 瀵逛簬鎵鏈夐潪const 綾誨瀷鍙互鏃犳潯浠惰漿鍖栦負(fù) const綾誨瀷錛屼絾鏄悗鑰呬笉鑳借嚜鍔ㄨ漿鍖栦負(fù)鍓嶈呴櫎闈炴樉寮忕殑寮哄埗杞寲鍘繪帀const鎬с傝繖鏍峰仛鏄湁鎰忎箟鐨勶紝鍥犱負(fù)const綾誨瀷鏄潪const鐨勪竴涓瓙闆嗘槸涓縐嶇壒孌婏紝鐢辨櫘閬嶈漿鍖栦負(fù)鐗規(guī)畩鏄悎鐞嗙殑錛屽氨璞℃ā鏉跨壒鍖栵紝緇ф壙鐨勫悜涓婃槧灝勯兘鏄湁鎰忎箟鐨勩?
<4> 璁頒綇鎵鏈塩onst淇グ鐨勫唴瀹瑰茍涓嶆槸姘歌繙涓嶅彲鏀瑰彉錛屽鏋滀漢涓虹殑寮哄埗杞寲緙栬瘧鍣ㄦ槸涓嶄細(xì)鎻愰啋鐨勩傚洜涓哄畠娌℃湁涔夊姟榪欎箞鍋氾紝鎵浠ユ垜浠鍏惰漿鍖栨椂瑕佸皬蹇?jī)銆?
<5> 鍦╟onst綾繪垚鍛樺嚱鏁板鐞嗘椂錛屾垜浠紩鍏ヤ簡(jiǎn)mutable淇グ綾繪垚鍛樺彉閲忥紝緇忚繃鍏朵慨楗扮殑鎴愬憳鍙橀噺鍙互鍦╟onst綾繪垚鍛樺嚱鏁頒腑琚慨鏀癸紝緙栬瘧鍣ㄦ槸鍏佽鐨勩傝屽叾浠栨湭琚玬utable淇グ鐨勬垚鍛樿繕鏄寜鐓onst瑙勫垯涓嶈兘鍦╟onst鎴愬憳鍑芥暟涓鏀瑰彉銆?
鍑芥暟鍚庨潰鍔犫渃onst鈥濅笌涓嶅姞鏄袱涓笉鍚屽嚱鏁幫紝濡傦細(xì)
(-127~-0 +0~127)鍏?/SPAN>256涓?/SPAN>.
鏈変簡(jiǎn)鏁板肩殑琛ㄧず鏂規(guī)硶灝卞彲浠ュ鏁拌繘琛岀畻鏈繍綆?/SPAN>.浣嗘槸寰堝揩灝卞彂鐜扮敤甯︾鍙蜂綅鐨勫師鐮佽繘琛屼箻闄よ繍綆楁椂緇撴灉姝g‘,鑰屽湪鍔犲噺榪愮畻鐨勬椂鍊欏氨鍑虹幇浜?jiǎn)闂?/SPAN>,濡備笅: 鍋囪瀛楅暱涓?/SPAN>8bits
( 1 ) 10- ( 1 )10 = ( 1 )10 + ( -1 )10 = ( 0 )10
(00000001)鍘?/SUB> + (10000001)鍘?SPAN style="POSITION: relative; TOP: 6pt; mso-text-raise: -6.0pt"> = (10000010)鍘?/SUB> = ( -2 )
鏄劇劧涓嶆紜?/SPAN>.鍥犱負(fù)鍦ㄤ袱涓暣鏁扮殑鍔犳硶榪愮畻涓槸娌℃湁闂鐨?/SPAN>,浜庢槸灝卞彂鐜伴棶棰樺嚭鐜板湪甯︾鍙蜂綅鐨勮礋鏁拌韓涓?/SPAN>,瀵歸櫎絎﹀彿浣嶅鐨勫叾浣欏悇浣嶉愪綅鍙栧弽灝變駭鐢熶簡(jiǎn)鍙嶇爜.鍙嶇爜鐨勫彇鍊肩┖闂村拰鍘熺爜鐩稿悓涓斾竴涓瀵瑰簲. 涓嬮潰鏄弽鐮佺殑鍑忔硶榪愮畻:
( 1 )10 - ( 1 ) 10= ( 1 ) 10+ ( -1 ) 10= ( 0 )10
(00000001) 鍙?/SUB>+ (11111110)鍙?/SUB> = (11111111)鍙?SPAN style="POSITION: relative; TOP: 6pt; mso-text-raise: -6.0pt"> = ( -0 )
( 1 )10 - ( 2)10 = ( 1 )10 + ( -2 )10 = ( -1 )10
(00000001) 鍙?/SUB>+ (11111101)鍙?/SUB> = (11111110)鍙?SPAN style="POSITION: relative; TOP: 6pt; mso-text-raise: -6.0pt"> = ( -1 )
姝g‘闂鍑虹幇鍦?/SPAN>(+0)鍜?/SPAN>(-0)涓?/SPAN>,鍦ㄤ漢浠殑璁$畻姒傚康涓浂鏄病鏈夋璐熶箣鍒嗙殑.(鍗板害浜洪鍏堝皢闆朵綔涓烘爣璁板茍鏀懼叆榪愮畻涔嬩腑,鍖呭惈鏈夐浂鍙風(fēng)殑鍗板害鏁板鍜屽崄榪涘埗璁℃暟瀵逛漢綾繪枃鏄庣殑璐$尞鏋佸ぇ).
浜庢槸灝卞紩鍏ヤ簡(jiǎn)琛ョ爜姒傚康. 璐熸暟鐨勮ˉ鐮佸氨鏄鍙嶇爜鍔犱竴,鑰屾鏁頒笉鍙?/SPAN>,姝f暟鐨勫師鐮佸弽鐮佽ˉ鐮佹槸涓鏍風(fēng)殑.鍦ㄨˉ鐮佷腑鐢?/SPAN>(-128)浠f浛浜?/SPAN>(-0),鎵浠ヨˉ鐮佺殑琛ㄧず鑼冨洿涓?/SPAN>:
(-128~0~127)鍏?/SPAN>256涓?/SPAN>.
娉ㄦ剰:(-128)娌℃湁鐩稿搴旂殑鍘熺爜鍜屽弽鐮?/SPAN>, (-128) = (10000000)
( 1 ) 10- ( 1 ) 10= ( 1 )10 + ( -1 )10 = ( 0 )10
(00000001)琛?/SUB> + (11111111)琛?/SUB> = (00000000)琛?SPAN style="POSITION: relative; TOP: 6pt; mso-text-raise: -6.0pt"> = ( 0 )
姝g‘( 1 ) 10- ( 2) 10= ( 1 )10 + ( -2 )10 = ( -1 )10
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