C语言函数大全

函数名：abort

功能：异常终止•个进程

用法：voidabort(void);

程序例：

#include<stdio.h>

ttinclude<stdlib.h>

intmain(void)

{

printf(''Callingabort()\nzz);

abort();

return0;/*Thisisneverreached*/

)

函数名：abs

功能：求整数的绝对值

用法：intabs(inti);

程序例：

ttinclude<stdio.h>

#include<math.h>

intmain(void)

(

intnumber=-1234;

printf("number:%dabsolutevalue:%d\n〃，number,abs(number));

return0;

)

函数名：absread,abswirte

功能：绝对磁盘扇区读、写数据

用法：intabsread(intdrive,intnsects,intsectno,void*buffer);

intabswrite(intdrive,intnsects,intsectno,void*buffer);

程序例：

/*absreadexample*/

#include<stdio.h>

ftinclude<conio.h>

#include<process.h>

ttinclude<dos.h>

intmain(void)

(

inti,strt,ch_out,sector;

charbuf[512];

printf(zzInsertadisketteintodriveAandpressanykey\n〃)；

getchO;

sector=0;

if(absread(0,1,sector,&buf)!=0)

{

perror(，zDiskproblem");

exit(1);

)

printf(，zRead0K\n");

strt=3;

for(i=0;i<80;i++)

(

chout=buf[strt+i];

putchar(ch_out);

}

printf(〃\n〃)；

return(0);

)

函数名：access

功能：确定文件的访问权限

用法：intaccess(constchar*filename,intamode);

程序例：

#include<stdio.h>

ftinclude<io.h>

intfile_exists(char*filename);

intmain(void)

(

printf(z，DoesNOTEXIST.FILexist:%s\n〃，

file_exists(，zNOTEXISTS.FIL，Z)?〃YES〃：〃N0〃)；

return0;

)

intfile_exists(char*filename)

{

return(access(filename,0)==0);

)

函数名：acos

功能：反余弦函数

用法：doubleacos(doublex);

程序例：

ttinclude<stdio.h>

ttinclude<math.h>

intmain(void)

(

doubleresult;

doublex=0.5;

result=acos(x);

printfC'Thearccosineof%lfis%lf\n/z,x,result);

return0;

函数名：allocmem

功能：分配DOS存储段

用法：intallocmem(unsignedsize,unsigned*seg);

程序例：

ttinclude<dos.h>

#include<alloc.h>

#include<stdio.h>

intmain(void)

{

unsignedintsize,segp;

intstat;

size=64;/*(64x16)=1024bytes*/

stat=allocmem(size,&segp);

if(stat==-1)

printf(^Allocatedmemoryatsegment:%x\n〃，segp);

else

printf(z，Failed:maximumnumberofparagraphsavailableis%u\n〃，

stat);

return0;

)

函数名：arc

功能：画一•弧线

用法：voidfararc(intx,inty,intstangle,intendangle,intradius);

程序例：

#include<graphics.h>

^include<stdlib.h>

ttinclude<stdio.h>

ftinclude<conio.h>

intmain(void)

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intmidx,midy;

intstangle=45,endangle=135;

intradius=100;

/*initializegraphicsandlocalvariables*/

initgraph(&gdriver,&gmode,;

/*readresultofinitialization*/

errorcode=graphresult();/*anerroroccurred*/

if(errorcode!=grOk)

{

printf(^Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf("Pressanykeytohalt:");

getch();

exit(1);/*terminatewithanerrorcode*/

midx=getmaxx()/2;

midy=getmaxy()/2;

setcolor(getmaxcolor());

/*drawarc*/

arc(midx,midy,stangle,endangle,radius);

/*cleanup*/

getch();

closegraph();

return0;

)

函数名:asctime

功能：转换日期和时间为ASCH码

用法：char*asctime(conststructtm*tblock);

程序例：

ftinclude<stdio.h>

ttinclude<string.h>

#include<time.h>

intmain(void)

(

structtmt;

charstr[80];

/*sampleloadingoftmstructure*/

t.tmsec=1;/*Seconds*/

t.tm_min=30;/*Minutes*/

t.tmhour=9;/*Hour*/

t.tmmday=22;/*DayoftheMonth*/

t.tm_mon=11;/*Month*/

t.tm_year=56;/*Year-doesnotincludecentury*/

t.tmwday=4;/*Dayoftheweek*/

t.tm_yday=0;/*Doesnotshowinasctime*/

t.tmisdst=0;/*IsDaylightSavTime;doesnotshowinasctime*/

/*convertsstructuretonullterminated

string*/

strcpy(str,asctime(&t));

printf(〃％s\n〃，str);

return0;

)

函数名:asin

功能：反正弦函数

用法：doubleasin(doublex);

程序例：

tfinclude<stdio.h>

ftinclude<math.h>

intmain(void)

{

doubleresult;

doublex=0.5;

result=asin(x);

printf(z，Thearcsinof%lfis%lf\nz，,x,result);

return(0);

)

函数名：assert

功能：测试一个条件并可能使程序终止

用法：voidassert(inttest);

程序例：

#include<assert.h>

ttinclude<stdio.h>

ttinclude<stdlib.h>

structITEM{

intkey;

intvalue;

};

/*additemtolist,makesurelistisnotnull*/

voidadditem(structITEM*itemptr){

assert(itemptr!=NULL);

/*additemtolist*/

)

intmain(void)

(

additem(NULL);

return0;

)

函数名：atan

功能：反正切函数

用法：doubleatan(doublex);

程序例：

tfinclude<stdio.h>

#include<math.h>

intmain(void)

(

doubleresult;

doublex=0.5;

result=atan(x);

printf(Z/Thearctangentof%lfis%lf\n〃，x,result);

return(0);

)

函数名:atan2

功能：计算Y/X的反正切值

用法：doubleatan2(doubley,doublex);

程序例：

#include<stdio.h>

#include<math.h>

intmain(void)

(

doubleresult;

doublex=90.0,y=45.0;

result=atan2(y,x);

printf("Thearctangentratioof%lfis%lf\n〃，(y/x),result);

return0;

)

函数名：atexit

功能：注册终止函数

用法：intatexit(atexittfunc);

程序例：

#include<stdio.h>

ttinclude<stdlib.h>

voidexit_fnl(void)

{

printf(，zExitfunction#1called\n,，);

)

voidexit_fn2(void)

(

printfC'Exitfunction#2called\n〃)；

intmain(void)

/*postexitfunction#1*/

atexit(exit_fnl);

/*postexitfunction#2*/

atexit(exit_fn2);

return0;

函数名：atof

功能：把字符串转换成浮点数

用法：doubleatof(constchar*nptr);

程序例：

tfinclude<stdlib.h>

ftinclude<stdio.h>

intmain(void)

(

floatf;

char*str="12345.67”;

f=atof(str);

printf(''string=%sfloat=%f\n〃，str,f);

return0;

)

函数名:atoi

功能：把字符串转换成长整型数

用法：intatoi(constchar*nptr);

程序例：

ftinclude<stdlib.h>

#include<stdio.h>

intmain(void)

(

intn;

char*str="12345.67”;

n=atoi(str);

printf("string=%sinteger=%d\n〃，str,n);

return0;

)

函数名：atol

功能：把字符串转换成长整型数

用法：longatol(constchar*nptr);

程序例：

#include<stdlib.h>

#include<stdio.h>

intmain(void)

(

long1;

char*str=”98765432〃；

1=atol(lstr);

printfC'string=%sinteger=%ld\n",str,1);

return(O);

函数名：bar

功能：画一个二维条形图

用法：voidfarbar(intleft,inttop,intright,intbottom);

程序例：

#include<graphics.h>

#include<stdlib.h>

#include<stdio.h>

#include<conio.h>

intmain(void)

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intmidx,midy,i;

/*initializegraphicsandlocalvariables*/

initgraph(&gdriver,&gmode,〃〃)；

/*readresultofinitialization*/

errorcode=graphresult();

if(errorcode!=grOk)/*anerroroccurred*/

(

printf(''Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf("Pressanykeytohalt:");

getch();

exit(1);/*terminatewithanerrorcode*/

)

midx=getmaxxO/2;

midy=getmaxy()/2;

/*loopthroughthefillpatterns*/

for(i=SOLID_FILL;i<USER_FILL;i++)

(

/*setthefillstyle*/

setfillstyle(i,getmaxcolor());

/*drawthebar*/

bar(midx-50,midy-50,midx+50,

midy+50);

getch();

)

/*cleanup*/

closegraph();

return0;

)

函数名：bar3d

功能：画一个三维条形图

用法：voidfarbar3d(intleft,inttop,intright,intbottom,

intdepth,inttopflag);

程序例:

#include<graphics.h>

#include<stdlib.h>

ttinclude<stdio.h>

#include<conio.h>

intmain(void)

(

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intmidx,midy,i;

/*initializegraphics,localvariables*/

initgraph(&gdriver,&gmode,〃〃)；

/*readresultofinitialization*/

errorcode=graphresult();

if(errorcode!=grOk)/*anerroroccurred*/

{

printf(''Graphicserror:%s\n，z,grapherrormsg(errorcode));

printf("Pressanykeytohalt:");

getch();

exit(1);/*terminatewitherrorcode*/

)

midx=getmaxx()/2;

midy=getmaxy()/2;

/*loopthroughthefillpatterns*/

for(i=EMPTY_FILL;i<USER_FILL;i++)

(

/*setthefillstyle*/

setfillstyle(i,getmaxcolor());

/*drawthe3-dbar*/

bar3d(midx-50,midy-50,midx+50,midy+50,10,1);

getch();

)

/*cleanup*/

closegraph();

return0;

)

函数名：bdos

功能：DOS系统调用

用法：intbdos(intdosfun,unsigneddosdx,unsigneddosal);

程序例：

#include<stdio.h>

#include<dos.h>

/*Getcurrentdriveas'A','B',...*/

charcurrentdrive(void)

(

charcurdrive;

/*Getcurrentdiskas0,1,…*/

curdrive=bdos(0x19,0,0);

return('A'+curdrive);

)

intmain(void)

(

printf(，zThecurrentdriveis%c:\n/z,current_drive());

return0;

函数名:bdosptr

功能：DOS系统调用

用法：intbdosptr(intdosfun,void*argument,unsigneddosal);

程序例：

ttinclude<string.h>

ftinclude<stdio.h>

#include<dir.h>

ftinclude<dos.h>

ttinclude<errno.h>

#include<stdlib.h>

ftdefineBUFLEN80

intmain(void)

charbuffer[BUFLEN];

inttest;

printf(，zEnterfullpathnameofadirectory、/');

gets(buffer);

test=bdosptr(0x3B,buffer,0);

if(test)

{

printf("DOSerrormessage:%d\n〃，errno);

/*Seeerrno.hforerrorlistings*/

exit(1);

)

getcwd(buffer,BUFLEN);

printf(z，Thecurrentdirectoryis:%s\n〃，buffer);

return0;

函数名：bioscom

功能：串行I/O通信

用法：intbioscom(intcmd,charabyte,intport);

程序例：

ttinclude<bios.h>

ftinclude<conio.h>

#defineCOM10

#defineDATA_READY0x100

#defineTRUE1

ftdefineFALSE0

#defineSETTINGS0x80|0x02|0x000x00)

intmain(void)

intin,out,status,DONE=FALSE;

bioscom(0,SETTINGS,COM1);

cprintf(z，...BIOSCOM[ESC]toexit…\n〃);

while(!D0NE)

(

status=bioscom(3,0,COM1);

if(status&DATA_READY)

if((out=bioscom(2,0,COM1)&0x7F)!=0)

putch(out);

if(kbhit())

(

if((in=getchO)=='\xlB')

DONE=TRUE;

bioscom(l,in,C0M1);

return0;

)

函数名：biosdisk

功能：软硬盘I/O

用法：intbiosdisk(intcmd,intdrive,inthead,inttrack,intsector

intnsects,void*buffer);

程序例：

#include<bios.h>

ttinclude<stdio.h>

intmain(void)

(

intresult;

charbuffer[512];

printf(""Testingtoseeifdrivea:isready\n〃)；

result=biosdisk(4,0,0,0,0,1,buffer);

result&=0x02;

(result)?(printf(，zDriveA:Ready\n〃)):

(printf(^DriveA:NotReady\n〃))；

return0;

函数名：biosequip

功能：检查设备

用法：intbiosequip(void);

程序例：

ttinclude<bios.h>

#include<stdio.h>

intmain(void)

intresult;

charbuffer[512];

printf(""Testingtoseeifdrivea:isready\n，/);

result=biosdisk(4,0,0,0,0,1,buffer);

result&=0x02;

(result)?(printf("DriveA:Ready'n")):

(printf(/zDriveA:NotReady\n/，));

return0;

函数名:bioskey

功能：直接使用BIOS服务的键盘接口

用法：intbioskey(intcmd);

程序例：

ttinclude<stdio.h>

#include<bios.h>

#include<ctype.h>

ftdefineRIGHT0x01

#defineLEFT0x02

#defineCTRL0x04

ttdefineALT0x08

intmain(void)

(

intkey,modifiers;

/*function1returns0untilakeyispressed*/

while(bioskey(1)==0);

/*function0returnsthekeythatiswaiting*/

key=bioskey(0);

/*usefunction2todetermineifshiftkeyswereused*/

modifiers=bioskey(2);

if(modifiers)

printf(〃[”);

if(modifiers&RIGHT)printffRIGHT");

if(modifiers&LEFT)printf("LEFT");

if(modifiers&CTRL)printf("CTRL");

if(modifiers&ALT)printf("ALT");

printf(〃]〃)；

)

/*printoutthecharacterread*/

if(isalnum(key&OxFF))

printf(〃'%cf\n〃，key);

else

printf(，z%#02x\n/z,key);

return0;

函数名：biosmemory

功能：返回存储块大小

用法：intbiosmemory(void);

程序例：

ttinclude<stdio.h>

ftinclude<bios.h>

intmain(void)

(

intmemory_size;

memorysize=biosmemory();/*returnsvalueupto640K*/

printf(Z，RAMsize=%dK\nz/,memory_size);

return0;

}

函数名:biosprint

功能：直接使用BIOS服务的打印机I/O

用法：intbiosprint(intcmd,intbyte,intport);

程序例：

#include<stdio.h>

^include<conio.h>

ttinclude<bios.h>

intmain(void)

#defineSTATUS2/*printerstatuscommand*/

#definePORTNUM0/*portnumberforLPT1*/

intstatus,abyte=0;

printf(^Pleaseturnoffyourprinter.Pressanykeytocontinue\n〃)；

getchO;

status=biosprint(STATUS,abyte,PORTNUM);

if(status&0x01)

printf(，zDevicetimeout.\n〃)；

if(status&0x08)

printf(z，I/0error.\n〃)；

if(status&0x10)

printf(",Selected.\n〃)；

if(status&0x20)

printf(z/Outofpaper.\n");

if(status&0x40)

printf(^Acknowledge.\n〃)；

if(status&0x80)

printf(^Notbusy.\n〃)；

return0;

函数名:biostime

功能：读取或设置BIOS时间

用法：longbiostime(intcmd,longnewtime);

程序例：

#include<stdio.h>

#include<bios.h>

ttinclude<time.h>

#include<conio.h>

intmain(void)

(

longbios_time;

clrscr();

cprintf(z，Thenumberofclocktickssincemidnightis:\r\n〃)；

cprintf(""Thenumberofsecondssincemidnightis:\r\n〃)；

cprintf(，zThenumberofminutessincemidnightis:\r\n，z);

cprintf(^Thenumberofhourssincemidnightis:\r\n〃)；

cprintf(/z\r\nPressanykeytoquit:");

while(!kbhit())

biostime=biostime(0,0L);

gotoxy(50,1);

cprintf(〃％lu〃，bios_time);

gotoxy(50,2);

cprintf(，z%.4f，z,bios_time/CLK_TCK);

gotoxy(50,3);

cprintf("%.4f〃,bios_time/CLK_TCK/60);

gotoxy(50,4);

cprintfC%.4f\bios_time/CLK_TCK/3600);

)

return0;

)

函数名：brk

功能：改变数据段空间分配

用法：intbrk(void*endds);

程序例：

ttinclude<stdio.h>

#include<alloc.h>

intmain(void)

(

char*ptr;

printf("Changingallocationwithbrk()\n〃)；

ptr=malloc(1);

printf(''Beforebrk()call:%lubytesfree\nzz,coreleft());

brk(ptr+1000);

printfCAfterbrk()call:%lubytesfree\n〃，coreleft());

return0;

)

函数名：bsearch

功能：二分法搜索

用法：void*bsearch(constvoid*key,constvoid*base,sizet*nelem,sizetwidth,

int(*fcmp)(constvoid*,const*));

程序例：

#include<stdlib.h>

ftinclude<stdio.h>

#defineNELEMS(arr)(sizeof(arr)/sizeof(arr[0]))

intnumarray[]={123,145,512,627,800,933);

intnumeric(constint*pl,constint*p2)

(

return(*pl-*p2);

)

intlookup(intkey)

(

int*itemptr;

/*Thecastof(int(*)(constvoidconstvoid*))

isneededtoavoidatypemismatcherrorat

compiletime*/

itemptr=bsearch(&key,numarray,NELEMS(numarray),

sizeof(int),(int(*)(constvoidconstvoid*))numeric);

return(itemptr!=NULL);

)

intmain(void)

(

if(lookup(512))

printf(，z512isinthetable.\nz，);

else

printf(，z512isn，tinthetable.\n〃)；

return0;

)

函数名:cabs

功能：计算复数的绝对值

用法：doublecabs(structcomplexz);

程序例：

#include<stdio.h>

tfinclude<math.h>

intmain(void)

(

structcomplexz;

doubleval;

z.x=2.0;

z.y=1.0;

val=cabs(z);

printf(〃Theabsolutevalueof%.21fi%.21fjis%.21f〃，z.x,z.y,val);

return0;

函数名：calloc

功能：分配主存储器

用法：void*calloc(size_tnelem,size_telsize);

程序例：

#include<stdio.h>

ttinclude<alloc.h>

intmain(void)

(

char*str=NULL;

/*allocatememoryforstring*/

str=calloc(10,sizeof(char));

/*copy〃Hello"intostring*/

strcpy(str,〃Hello〃)；

/*displaystring*/

printf(''Stringis%s\n〃，str);

/*freememory*/

free(str);

return0;

函数名：ceil

功能：向上舍入

用法：doubleceil(doublex);

程序例：

#include<math.h>

#include<stdio.h>

intmain(void)

(

doublenumber=123.54;

doubledown,up;

down=floor(number);

up=ceil(number);

printf(''originalnumber%5.21f\nzz,number);

printf(^numberroundeddown%5.21f\n〃，down);

printf("numberroundedup%5.21f\n",up);

return0;

)

函数名:cgets

功能：从控制台读字符串

用法：char*cgets(char*str);

程序例：

ftinclude<stdio.h>

#include<conio.h>

intmain(void)

(

charbuffer[83];

char*p;

/*There'sspacefor80charactersplustheNULLterminator*/

buffer[0]=81;

printf("Inpulsomechars:");

p=cgets(buffer);

printf(z/\ncgetsread%dcharacters:\〃%s\〃\n〃，buffer[1],p);

printf("Thereturnedpointeris%p,buffer[0]isat%p\n〃，p,&buffer);

/*Leaveroomfor5charactersplustheNULLterminator*/

buffer[0]=6;

printf(^Inputsomechars:");

p二cgets(buffer);

printf(^\ncgetsread%dcharacters:\〃％s\〃\n〃，buffer[l],p);

printf(，zThereturnedpointeris%p,buffer[0]isat%p\n〃，p,ftbuffer);

return0;

函数名：chdir

功能：改变工作目录

用法：intchdir(constchar*path);

程序例：

#include<stdio.h>

#include<stdlib.h>

#include<dir.h>

charold_dir[MAXDIR];

charnewdir[MAXDIR];

intmain(void)

(

if(getcurdir(0,old_dir))

(

perror("getcurdir()〃);

exit(1);

)

printf(z，Currentdirectoryis:\\%s\nz，,old_dir);

if(chdir(〃\\"))

(

perror("chdir()〃)；

exit(1);

)

if(getcurdir(0,new_dir))

(

perror("getcurdir()〃)；

exit(1);

printf(^Currentdirectoryisnow:\\%s\n”,newdir);

printf(〃\nChangingbacktoorignaldirectory:\\%s\n〃，olddir);

if(chdir(old_dir))

(

perror("chdir()〃)；

exit(1);

)

return0;

)

函数名：_chmod,chmod

功能：改变文件的访问方式

用法：intchmod(constchar"filename,intpermiss);

程序例：

#include<sys\stat.h>

#include<stdio.h>

#include<io.h>

voidmakereadonly(char*filename);

intmain(void)

(

makeread.only("NOTEXIST.FIL〃)；

make_read_only(''MYFILE.FILZ，);

return0;

)

voidmake_read_only(char*filename)

(

intstat;

stat=chmod(filename,S_IREAD);

if(stat)

printf(，/Couldn，tmake%sread-only\n，z,filename);

else

printf("Made%sread-only\n,，,filename);

)

函数名：chsize

功能：改变文件大小

用法：intchsize(inthandle,longsize);

程序例：

#include<string.h>

#include<fcntl.h>

#include<io.h>

intmain(void)

(

inthandle;

charbuf[ll]="0123456789〃；

/*createtextfilecontaining10bytes*/

handle=open("DUMMY.FIL",0_CREAT);

write(handle,buf,strlen(buf));

/*truncatethefileto5bytesinsize*/

chsize(handle,5);

/*closethefile*/

close(handle);

return0;

函数名:circle

功能：在给定半径以(x,y)为圆心画圆

用法：voidfarcircle(intx,inty,intradius);

程序例：

#include<graphics.h>

#include<stdlib.h>

ttinclude<stdio.h>

ftinclude<conio.h>

intmain(void)

{

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intmidx,midy;

intradius=100;

/*initializegraphicsandlocalvariables*/

initgraph(&gdriver,&gmode,;

/*readresultofinitialization*/

errorcode=graphresult0;

if(errorcode!=grOk)/*anerroroccurred*/

(

printf(''Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf(z，Pressanykeytohalt:");

getchO;

exit(1);/*terminatewithanerrorcode*/

)

midx=getmaxx()/2;

midy=getmaxy()/2;

setcolor(getmaxcolor());

/*drawthecircle*/

circle(midx,midy,radius);

/*cleanup*/

getchO;

closegraph();

return0;

函数名：cleardevice

功能：清除图形屏幕

用法：voidfarcleardevice(void);

程序例：

#include<graphics.h>

#include<stdlib.h>

#include<stdio.h>

#include<conio.h>

intmain(void)

(

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intmidx,midy;

/*initializegraphicsandlocalvariables*/

initgraph(&gdriver,&gmode,〃〃)；

/*readresultofinitialization*/

errorcode二graphresult();

if(errorcode!=grOk)/*anerroroccurred*/

{

printf(''Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf("Pressanykeytohalt:");

getchO;

exit(1);/*terminatewithanerrorcode*/

)

midx=getmaxxO/2;

midy=getmaxy()/2;

setcolor(getmaxcolor());

/*forcenteringscreenmessages*/

settextjustify(CENTERTEXT,CENTERTEXT);

/*outputamessagetothescreen*/

outtextxy(midx,midy,“pressanykeytoclearthescreen:");

/*waitforakey*/

getchO;

/*clearthescreen*/

cleardevice();

/*outputanothermessage*/

outtextxy(midx,midy,“pressanykeytoquit:");

/*cleanup*/

getchO；

closegraph();

return0;

函数名：clearerr

功能：复位错误标志

用法：voidclearerr(FILE*stream);

程序例：

#include<stdio.h>

intmain(void)

FILE*fp;

charch;

/*openafileforwriting*/

fp=fopen("DUMMY.FIL",〃w〃);

/*forceanerrorconditionbyattemptingtoread*/

ch二fgetc(fp);

printf(z，%c\nz/,ch);

if(ferror(fp))

(

/*displayanerrormessage*/

printf(z，ErrorreadingfromDUMMY.FIL\n");

/*resettheerrorandEOFindicators*/

clearerr(fp);

)

fclose(fp);

return0;

函数名：clearviewport

功能：清除图形视区

用法：voidfarclearviewport(void);

程序例：

tfinclude<graphics.h>

ttinclude<stdlib.h>

#include<stdio.h>

ttinclude<conio.h>

#defineCLIPON1/*activatesclippinginviewport*/

intmain(void)

(

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intht;

/*initializegraphicsandlocalvariables*/

initgraph(&gdriver,&gmode,〃〃)；

/*readresultofinitialization*/

errorcode=graphresult();

if(errorcode!=grOk)/*anerroroccurred*/

printf(''Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf("Pressanykeytohalt:");

getch();

exit(1);/*terminatewithanerrorcode*/

)

setcolor(getmaxcolor());

ht=textheight(〃W〃)；

/*messageindefaultfull-screenviewport*/

outtextxy(0,0,〃*<一(0,0)indefaultviewport");

/*createasmallerviewport*/

setviewport(50,50,getmaxxO-50,getmaxy()-50,CLIPON);

/*displaysomemessages*/

outtextxy(0,0,〃*<一(0,0)insmallerviewport");

outtextxy(0,2*ht,“Pressanykeytoclearviewport/');

/*waitforakey*/

getch();

/*cleartheviewport*/

clearviewport();

/*outputanothermessage*/

outtextxy(0,0,"Pressanykeytoquit:");

/*cleanup*/

getch();

closegraph();

return0;

函数名：_close,close

功能：关闭文件句柄

用法：intclose(inthandle);

程序例：

ftinclude<string.h>

#include<stdio.h>

#include<fcntl.h>

tfinclude<io.h>

main()

inthandle;

charbuf[ll]="0123456789〃；

/*createafilecontaining10bytes*/

handle=open("NEW.FIL",O_CREAT);

if(handle>-1)

(

write(handle,buf,strlen(buf));

/*closethefile*/

close(handle);

)

else

(

printf(z，Erroropeningfile\n〃)；

)

return0;

)

函数名：clock

功能：确定处理器时间

用法：clock_tclock(void);

程序例：

ttinclude<time.h>

#include<stdio.h>

#include<dos.h>

intmain(void)

(

clock_tstart,end;

start=clock();

delay(2000);

end=clock();

printf(/zThetimewas:(end-start)/CLKTCK);

return0;

函数名:closegraph

功能：关闭图形系统

用法：voidfarclosegraph(void);

程序例：

tfinclude<graphics.h>

#include<stdlib.h>

#include<stdio.h>

#include<conio.h>

intmain(void)

(

/*requestautodetection*/

intgdriver=DETECT,gmode,errorcode;

intx,y;

/*initializegraphicsmode*/

initgraph(&gdriver,&gmode,〃〃)；

/*readresultofinitialization*/

errorcode=graphresult();

if(errorcode!=grOk)/*anerror

occurred*/

(

printf(''Graphicserror:%s\n〃，grapherrormsg(errorcode));

printf(Z/Pressanykeytohalt:");

getchO;

exit(1);/*terminatewithanerrorcode*/

)

x=getmaxx()/2;

y=getmaxy()/2;

/*outputamessage*/

settextjustify(CENTER_TEXT,CENTER_TEXT);

outtextxy(x,y,"Pressakeytoclosethegraphicssystem:z，);

/*waitforakey*/

getchO;

/*closesdownthegraphicssystem*/

closegraph();

printf(//We，renowbackintextmode.\n〃)；

printf("Pressanykeytohalt：z，);

getchO;

return0;

)

函数名：clreol

功能：在文本窗口中清除字符到行末

用法：voidclreol(void);

程序例：

^include<conio.h>

intmain(void)

(

clrscr();

cprintf(，zThefunctionCLREOLclearsallcharactersfromthe\r\n〃)；

cprintf(z，cursorpositiontotheendofthelinewithinthe\r\n〃)；

cprintf(，zcurrenttextwindow,withoutmovingthecursor.\r\n，z);

cprintfC'Pressanykeytocontinue...〃)；

gotoxy(14,4);

getchO;

clreol();

getchO;

return0;

)

函数名:clrscr

功能：清除文本模式窗口

用法:voidclrscr(void);

程序例：

tfinclude<conio.h>

intmain(void)

inti;

clrscr();

for(i=0;i<20;i++)

cprintf(〃%d\r\n〃，i);

cprintf(〃\r\nPressanykeytoclearscreen");

getchO;

clrscr();

cprintf(""Thescreenhasbeencleared!z，);

getchO;

return0;

函数名：coreleft

功能：返回未使用内存的大小

用法：unsignedcoreleft(void);

程序例：

#include<stdio.h>

ttinclude<alloc.h>

intmain(void)

(

printf(〃Thedifferencebetweenthehighestallocatedblockand\nz，);

printf(，/thetopoftheheapis:%lubytes\n〃，(unsignedlong)coreleft());

return0;

函数名：cos

功能：余弦函数

用法：doublecos(doublex);

程序例：

#include<stdio.h>

tfinclude<math.h>

intmain(