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1、優(yōu)先級及預(yù)處理優(yōu)先級問題表達(dá)式經(jīng)常誤認(rèn)為的結(jié)果實(shí)際結(jié)果?的優(yōu)先級高于*-＞操作符用于消除這個(gè)問題fp所指對象的字段f(*p).f對P取f偏移，作為指針，然后進(jìn)行解除引用操作。*(p.f)[]高于*int*ap二ap是個(gè)指向int數(shù)組的指針int(*ap)ap是個(gè)元素為int指針的數(shù)組int*(ap[])函數(shù)()高于*int*fp()fp是個(gè)函數(shù)指針，所指函數(shù)返回intoint(*fp)0fp是個(gè)函數(shù)，返回int*int*(fp())==和!二高于位操作(val&mask!=0)(val&mask)!=0val&(ma
2、sk!=0)==和!二高于賦值符c=getchar()!=EOF(c=getchar())!=EOFc=(getchar()!=EOF)算術(shù)運(yùn)算符高于位移運(yùn)算符msb<<4+lsb(msb<<4)+lsbmsb<<(4+lsb)逗號運(yùn)算符在所有運(yùn)算符中優(yōu)先級最低i=1,2i=(1,2)(i=1),2表(3.1)預(yù)處理指令預(yù)處理名稱意義^define宏定義#undef撤銷已定義過的宏名^include使編譯程序?qū)⒘硪辉次募度氲綆в衖nclude的源文件中#if^if的一股令義是如果方「后面的襯量表達(dá)式為true.K編
3、澤它與-endifZ.間的代碼.否則跳過這些代碼.命令#endif標(biāo)識個(gè)#if塊的結(jié)束.-else命令的功能有點(diǎn)象C語肓中的else,丸Isc建立另一選擇(在袴i「失敗的情況下).衩li「命令意義與elseif同，它形成一個(gè)ifelse-if階梯狀語句，可進(jìn)行多種編譯選擇.#else#elif#endif#ifdef用#ifdef與和'ndcl、金令分別表示“如果有定文“及“婦果無定文”?是條件編譯的另一種方法。#ifndef#iine改變當(dāng)前行數(shù)和文件名稱.它們是在編澤程序中預(yù)先定義的標(biāo)識符命令的基本形式如下：rr
4、linenumberf'filename"]terror編澤程序時(shí).只要遇到terror就會生成一個(gè)編澤錯(cuò)誤提示消息.并停止編譯^pragma為實(shí)觀時(shí)定義的命令.它允許向編澤程序傳送務(wù)種指令例如.編譯程序可能有一種選擇.它又持對程序執(zhí)疔的銀蹤.可用pragma語句指定一個(gè)報(bào)蹤選擇°另外ANSI標(biāo)準(zhǔn)C還定義了如下兒個(gè)宏：_LINE_表示正在編譯的文件的行號_FILE_表示正在編譯的文件的名字_DATE_表示編譯時(shí)刻的I」期字符串，例如：“25Dec2007“_TIME_表示編譯時(shí)刻的時(shí)間字符串,例如：”12:30:55
5、“_STDC_判斷該文件是不是定義成標(biāo)準(zhǔn)C程序函數(shù)atoi與atof函數(shù)名：atoi功能：把字符串轉(zhuǎn)換成長整型數(shù)JIJ彳去：intatoi(constchar*nptr);程序例：ixnixmiuuhxuxmiloxix"xuxmiaxxjuxjjxuixuiixjjxxjjuuixjxumumumi』』』』xuixuiixjjxuiuixxxmiumTTTTTTTTTTTTTTTTTrTTIITrTrTrTTTTTrTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTrrtrTrTTTfTT
6、TTTTTT~TTTTTTTTTTTTTTTTTT"xxTTTTTTTTTTTTTTTTTT~TT~TT~TTTTTTTTTTTTTlTrTTYrTTTrTrTTjTTrIttjTt11HHTT11itTfTtttItTfTr11Ittj11H7TTrTrTTTrTrTrTrTrTrTr11JITfTT11JiTfTTHf!TTr!TrTrTrTrTr7TffJfjt7TTrTrTTTrTrTrTrTrffJiITIfIT11HTTTf11TrTrTr#includeintmain(void){i
7、ntn;char*str=n12345.67H;n=atoi(str);printf(,fstring=%sinteger=%d*str,n);return0;}ixixulx』』xiixixuixxxmiuixixiiHixxxixumix11xxumiixuuaunixjxumixoiuuxxunnma1x11nixixuTTTTTTTTTT~TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTrrrrTTTTTTTTTTTTTTTTrrxrTTTTrr"TTTTTTTTTTTTrrxrTT
8、TTTTTTTrTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTrTTTrTTTrTTTTTTTTTT~TtTrTTTTTTff11TrTTttttttttttttttttttttTTTTTTTitTiTtTTTttttttttTtttttttttTttTTTTTTTTTTrTTTTTr7TtTtttTTTjTITttTTTrTT
