函数名:?cabs?

功??能:?计算复数的绝对值?

用??法:?double?cabs(struct?complex?z);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
int?main(void)?
{?
???struct?complex?z;?
???double?val;?
???z.x?=?2.0;?
???z.y?=?1.0;?
???val?=?cabs(z);?
???printf("The?absolute?value?of?%.2lfi?%.2lfj?is?%.2lf",?z.x,?z.y,?val);?
???return?0;?
}?
??
??
??

函数名:?calloc?

功??能:?分配主存储器?

用??法:?void?*calloc(size_t?nelem,?size_t?elsize);?

程序例:?

#include?<stdio.h>?
#include?<alloc.h>?
int?main(void)?
{?
???char?*str?=?NULL;?
???/*?allocate?memory?for?string?*/?
???str?=?calloc(10,?sizeof(char));?
???/*?copy?"Hello"?into?string?*/?
???strcpy(str,?"Hello");?
???/*?display?string?*/?
???printf("String?is?%s\n",?str);?
???/*?free?memory?*/?
???free(str);?
???return?0;?
}?
??
??
??

函数名:?ceil?

功??能:?向上舍入?

用??法:?double?ceil(double?x);?

程序例:?

#include?<math.h>?
#include?<stdio.h>?
int?main(void)?
{?
???double?number?=?123.54;?
???double?down,?up;?
???down?=?floor(number);?
???up?=?ceil(number);?
???printf("original?number?????%5.2lf\n",?number);?
???printf("number?rounded?down?%5.2lf\n",?down);?
???printf("number?rounded?up???%5.2lf\n",?up);?
???return?0;?
}?
??
??
??

函数名:?cgets?

功??能:?从控制台读字符串?

用??法:?char?*cgets(char?*str);?

程序例:?

#include?<stdio.h>?
#include?<conio.h>?
int?main(void)?
{?
???char?buffer[83];?
???char?*p;?
???/*?There‘s?space?for?80?characters?plus?the?NULL?terminator?*/?
???buffer[0]?=?81;?
???printf("Input?some?chars:");?
???p?=?cgets(buffer);?
???printf("\ncgets?read?%d?characters:?\"%s\"\n",?buffer[1],?p);?
???printf("The?returned?pointer?is?%p,?buffer[0]?is?at?%p\n",?p,?&buffer);?
???/*?Leave?room?for?5?characters?plus?the?NULL?terminator?*/?
???buffer[0]?=?6;?
???printf("Input?some?chars:");?
???p?=?cgets(buffer);?
???printf("\ncgets?read?%d?characters:?\"%s\"\n",?buffer[1],?p);?
???printf("The?returned?pointer?is?%p,?buffer[0]?is?at?%p\n",?p,?&buffer);?
???return?0;?
}?
??
??
??

函数名:?chdir?

功??能:?改变工作目录?

用??法:?int?chdir(const?char?*path);?

程序例:?

#include?<stdio.h>?
#include?<stdlib.h>?
#include?<dir.h>?
char?old_dir[MAXDIR];?
char?new_dir[MAXDIR];?
int?main(void)?
{?
???if?(getcurdir(0,?old_dir))?
???{?
??????perror("getcurdir()");?
??????exit(1);?
???}?
???printf("Current?directory?is:?\\%s\n",?old_dir);?
???if?(chdir("\\"))?
???{?
??????perror("chdir()");?
??????exit(1);?
???}?
???if?(getcurdir(0,?new_dir))?
???{?
??????perror("getcurdir()");?
??????exit(1);?
???}?
???printf("Current?directory?is?now:?\\%s\n",?new_dir);?
???printf("\nChanging?back?to?orignal?directory:?\\%s\n",?old_dir);?
???if?(chdir(old_dir))?
???{?
??????perror("chdir()");?
??????exit(1);?
???}?
???return?0;?
}?
??
??

函数名:?_chmod,?chmod?

功??能:?改变文件的访问方式?

用??法:?int?chmod(const?char?*filename,?int?permiss);?

程序例:?

#include?<sys\stat.h>?
#include?<stdio.h>?
#include?<io.h>?
void?make_read_only(char?*filename);?
int?main(void)?
{?
???make_read_only("NOTEXIST.FIL");?
???make_read_only("MYFILE.FIL");?
???return?0;?
}?
void?make_read_only(char?*filename)?
{?
???int?stat;?
???stat?=?chmod(filename,?S_IREAD);?
???if?(stat)?
??????printf("Couldn‘t?make?%s?read-only\n",?filename);?
???else?
??????printf("Made?%s?read-only\n",?filename);?
}?
??
??
??

函数名:?chsize?

功??能:?改变文件大小?

用??法:?int?chsize(int?handle,?long?size);?

程序例:?

#include?<string.h>?
#include?<fcntl.h>?
#include?<io.h>?
int?main(void)?
{?
???int?handle;?
???char?buf[11]?=?"0123456789";?
???/*?create?text?file?containing?10?bytes?*/?
???handle?=?open("DUMMY.FIL",?O_CREAT);?
???write(handle,?buf,?strlen(buf));?
???/*?truncate?the?file?to?5?bytes?in?size?*/?
???chsize(handle,?5);?
???/*?close?the?file?*/?
???close(handle);?
???return?0;?
}?
??
??

函数名:?circle?

功??能:?在给定半径以(x,?y)为圆心画圆?

用??法:?void?far?circle(int?x,?int?y,?int?radius);?

程序例:?

#include?<graphics.h>?
#include?<stdlib.h>?
#include?<stdio.h>?
#include?<conio.h>?
int?main(void)?
{?
???/*?request?auto?detection?*/?
???int?gdriver?=?DETECT,?gmode,?errorcode;?
???int?midx,?midy;?
???int?radius?=?100;?
???/*?initialize?graphics?and?local?variables?*/?
???initgraph(&gdriver,?&gmode,?"");?
???/*?read?result?of?initialization?*/?
???errorcode?=?graphresult();?
???if?(errorcode?!=?grOk)??/*?an?error?occurred?*/?
???{?
??????printf("Graphics?error:?%s\n",?grapherrormsg(errorcode));?
??????printf("Press?any?key?to?halt:");?
??????getch();?
??????exit(1);?/*?terminate?with?an?error?code?*/?
???}?
???midx?=?getmaxx()?/?2;?
???midy?=?getmaxy()?/?2;?
???setcolor(getmaxcolor());?
???/*?draw?the?circle?*/?
???circle(midx,?midy,?radius);?
???/*?clean?up?*/?
???getch();?
???closegraph();?
???return?0;?
}?
??
??
??

函数名:?cleardevice?

功??能:?清除图形屏幕?

用??法:?void?far?cleardevice(void);?

程序例:?

#include?<graphics.h>?
#include?<stdlib.h>?
#include?<stdio.h>?
#include?<conio.h>?
int?main(void)?
{?
???/*?request?auto?detection?*/?
???int?gdriver?=?DETECT,?gmode,?errorcode;?
???int?midx,?midy;?
???/*?initialize?graphics?and?local?variables?*/?
???initgraph(&gdriver,?&gmode,?"");?
???/*?read?result?of?initialization?*/?
???errorcode?=?graphresult();?
???if?(errorcode?!=?grOk)??/*?an?error?occurred?*/?
???{?
??????printf("Graphics?error:?%s\n",?grapherrormsg(errorcode));?
??????printf("Press?any?key?to?halt:");?
??????getch();?
??????exit(1);?/*?terminate?with?an?error?code?*/?
???}?
???midx?=?getmaxx()?/?2;?
???midy?=?getmaxy()?/?2;?
???setcolor(getmaxcolor());?
???/*?for?centering?screen?messages?*/?
???settextjustify(CENTER_TEXT,?CENTER_TEXT);?
???/*?output?a?message?to?the?screen?*/?
???outtextxy(midx,?midy,?"press?any?key?to?clear?the?screen:");?
???/*?wait?for?a?key?*/?
???getch();?
???/*?clear?the?screen?*/?
???cleardevice();?
???/*?output?another?message?*/?
???outtextxy(midx,?midy,?"press?any?key?to?quit:");?
???/*?clean?up?*/?
???getch();?
???closegraph();?
???return?0;?
}?
??
??
??

函数名:?clearerr?

功??能:?复位错误标志?

用??法:void?clearerr(FILE?*stream);?

程序例:?

#include?<stdio.h>?
int?main(void)?
{?
???FILE?*fp;?
???char?ch;?
???/*?open?a?file?for?writing?*/?
???fp?=?fopen("DUMMY.FIL",?"w");?
???/*?force?an?error?condition?by?attempting?to?read?*/?
???ch?=?fgetc(fp);?
???printf("%c\n",ch);?
???if?(ferror(fp))?
???{?
??????/*?display?an?error?message?*/?
??????printf("Error?reading?from?DUMMY.FIL\n");?
??????/*?reset?the?error?and?EOF?indicators?*/?
??????clearerr(fp);?
???}?
???fclose(fp);?
???return?0;?
}?
??
??
??

函数名:?clearviewport?

功??能:?清除图形视区?

用??法:?void?far?clearviewport(void);?

程序例:?

#include?<graphics.h>?
#include?<stdlib.h>?
#include?<stdio.h>?
#include?<conio.h>?
#define?CLIP_ON?1???/*?activates?clipping?in?viewport?*/?
int?main(void)?
{?
???/*?request?auto?detection?*/?
???int?gdriver?=?DETECT,?gmode,?errorcode;?
???int?ht;?
???/*?initialize?graphics?and?local?variables?*/?
???initgraph(&gdriver,?&gmode,?"");?
???/*?read?result?of?initialization?*/?
???errorcode?=?graphresult();?
???if?(errorcode?!=?grOk)??/*?an?error?occurred?*/?
???{?
??????printf("Graphics?error:?%s\n",?grapherrormsg(errorcode));?
??????printf("Press?any?key?to?halt:");?
??????getch();?
??????exit(1);?/*?terminate?with?an?error?code?*/?
???}?
???setcolor(getmaxcolor());?
???ht?=?textheight("W");?
???/*?message?in?default?full-screen?viewport?*/?
???outtextxy(0,?0,?"*?<--?(0,?0)?in?default?viewport");?
???/*?create?a?smaller?viewport?*/?
???setviewport(50,?50,?getmaxx()-50,?getmaxy()-50,?CLIP_ON);?
???/*?display?some?messages?*/?
???outtextxy(0,?0,?"*?<--?(0,?0)?in?smaller?viewport");?
???outtextxy(0,?2*ht,?"Press?any?key?to?clear?viewport:");?
???/*?wait?for?a?key?*/?
???getch();?
???/*?clear?the?viewport?*/?
???clearviewport();?
???/*?output?another?message?*/?
???outtextxy(0,?0,?"Press?any?key?to?quit:");?
???/*?clean?up?*/?
???getch();?
???closegraph();?
???return?0;?
}?
??
??
??

函数名:?_close,?close?

功??能:?关闭文件句柄?

用??法:?int?close(int?handle);?

程序例:?

#include?<string.h>?
#include?<stdio.h>?
#include?<fcntl.h>?
#include?<io.h>?
main()?
{?
???int?handle;?
???char?buf[11]?=?"0123456789";?
???/*?create?a?file?containing?10?bytes?*/?
???handle?=?open("NEW.FIL",?O_CREAT);?
???if?(handle?>?-1)?
???{?
???????write(handle,?buf,?strlen(buf));?
???????/*?close?the?file?*/?
???????close(handle);?
???}?
???else?
???{?
???????printf("Error?opening?file\n");?
???}?
???return?0;?
}?
??
??
??

函数名:?clock?

功??能:?确定处理器时间?

用??法:?clock_t?clock(void);?

程序例:?

#include?<time.h>?
#include?<stdio.h>?
#include?<dos.h>?
int?main(void)?
{?
???clock_t?start,?end;?
???start?=?clock();?
???delay(2000);?
???end?=?clock();?
???printf("The?time?was:?%f\n",?(end?-?start)?/?CLK_TCK);?
???return?0;?
}?
??
??
??

函数名:?closegraph?

功??能:?关闭图形系统?

用??法:?void?far?closegraph(void);?

程序例:?

#include?<graphics.h>?
#include?<stdlib.h>?
#include?<stdio.h>?
#include?<conio.h>?
int?main(void)?
{?
???/*?request?auto?detection?*/?
???int?gdriver?=?DETECT,?gmode,?errorcode;?
???int?x,?y;?
???/*?initialize?graphics?mode?*/?
???initgraph(&gdriver,?&gmode,?"");?
???/*?read?result?of?initialization?*/?
???errorcode?=?graphresult();?
???if?(errorcode?!=?grOk)??/*?an?error?
??????occurred?*/?
???{?
??????printf("Graphics?error:?%s\n",?grapherrormsg(errorcode));?
??????printf("Press?any?key?to?halt:");?
??????getch();?
??????exit(1);?/*?terminate?with?an?error?code?*/?
???}?
???x?=?getmaxx()?/?2;?
???y?=?getmaxy()?/?2;?
???/*?output?a?message?*/?
???settextjustify(CENTER_TEXT,?CENTER_TEXT);?
???outtextxy(x,?y,?"Press?a?key?to?close?the?graphics?system:");?
???/*?wait?for?a?key?*/?
???getch();?
???/*?closes?down?the?graphics?system?*/?
???closegraph();?
???printf("We‘re?now?back?in?text?mode.\n");?
???printf("Press?any?key?to?halt:");?
???getch();?
???return?0;?
}?
??
??
??

函数名:?clreol?

功??能:?在文本窗口中清除字符到行末?

用??法:?void?clreol(void);?

程序例:?

#include?<conio.h>?
int?main(void)?
{?
???clrscr();?
???cprintf("The?function?CLREOL?clears?all?characters?from?the\r\n");?
???cprintf("cursor?position?to?the?end?of?the?line?within?the\r\n");?
???cprintf("current?text?window,?without?moving?the?cursor.\r\n");?
???cprintf("Press?any?key?to?continue?.?.?.");?
???gotoxy(14,?4);?
???getch();?
???clreol();?
???getch();?
???return?0;?
}?
??
??
??

函数名:?clrscr?

功??能:?清除文本模式窗口?

用??法:?void?clrscr(void);?

程序例:?

#include?<conio.h>?
int?main(void)?
{?
???int?i;?
???clrscr();?
???for?(i?=?0;?i?<?20;?i++)?
??????cprintf("%d\r\n",?i);?
???cprintf("\r\nPress?any?key?to?clear?screen");?
???getch();?
???clrscr();?
???cprintf("The?screen?has?been?cleared!");?
???getch();?
???return?0;?
}?
??
??
??

函数名:?coreleft?

功??能:?返回未使用内存的大小?

用??法:?unsigned?coreleft(void);?

程序例:?

#include?<stdio.h>?
#include?<alloc.h>?
int?main(void)?
{?
???printf("The?difference?between?the?highest?allocated?block?and\n");?
???printf("the?top?of?the?heap?is:?%lu?bytes\n",?(unsigned?long)?coreleft());?
???return?0;?
}?
??

函数名:?cos?

功??能:?余弦函数?

用??法:?double?cos(double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
int?main(void)?
{?
???double?result;?
???double?x?=?0.5;?
???result?=?cos(x);?
???printf("The?cosine?of?%lf?is?%lf\n",?x,?result);?
???return?0;?
}?
??
??
??

函数名:?cosh?

功??能:?双曲余弦函数?

用??法:?dluble?cosh(double?x);?

程序例:?

#include?<stdio.h>?
#include?<math.h>?
int?main(void)?
{?
???double?result;?
???double?x?=?0.5;?
???result?=?cosh(x);?
???printf("The?hyperboic?cosine?of?%lf?is?%lf\n",?x,?result);?
???return?0;?
}?
??
??
??

函数名:?country?

功??能:?返回与国家有关的信息?

用??法:?struct?COUNTRY?*country(int?countrycode,?struct?country?*country);?

程序例:?

#include?<dos.h>?
#include?<stdio.h>?
#define?USA?0?
int?main(void)?
{?
???struct?COUNTRY?country_info;?
???country(USA,?&country_info);?
???printf("The?currency?symbol?for?the?USA?is:?%s\n",?
???????????country_info.co_curr);?
???return?0;?
}?
??
??
??

函数名:?cprintf?

功??能:?送格式化输出至屏幕?

用??法:?int?cprintf(const?char?*format[,?argument,?...]);?

程序例:?

#include?<conio.h>?
int?main(void)?
{?
???/*?clear?the?screen?*/?
???clrscr();?
???/*?create?a?text?window?*/?
???window(10,?10,?80,?25);?
???/*?output?some?text?in?the?window?*/?
???cprintf("Hello?world\r\n");?
???/*?wait?for?a?key?*/?
???getch();?
???return?0;?
}?
??
??
??

函数名:?cputs?

功??能:?写字符到屏幕?

用??法:?void?cputs(const?char?*string);?

程序例:?

#include?<conio.h>?
int?main(void)?
{?
???/*?clear?the?screen?*/?
???clrscr();?
???/*?create?a?text?window?*/?
???window(10,?10,?80,?25);?
???/*?output?some?text?in?the?window?*/?
???cputs("This?is?within?the?window\r\n");?
???/*?wait?for?a?key?*/?
???getch();?
???return?0;?
}?
??
??
??

函数名:?_creat??creat?

功??能:?创建一个新文件或重写一个已存在的文件?

用??法:?int?creat?(const?char?*filename,?int?permiss);?

程序例:?

#include?<sys\stat.h>?
#include?<string.h>?
#include?<fcntl.h>?
#include?<io.h>?
int?main(void)?
{?
???int?handle;?
???char?buf[11]?=?"0123456789";?
???/*?change?the?default?file?mode?from?text?to?binary?*/?
???_fmode?=?O_BINARY;?
???/*?create?a?binary?file?for?reading?and?writing?*/?
???handle?=?creat("DUMMY.FIL",?S_IREAD?|?S_IWRITE);?
???/*?write?10?bytes?to?the?file?*/?
???write(handle,?buf,?strlen(buf));?
???/*?close?the?file?*/?
???close(handle);?
???return?0;?
}?
??

函数名:?creatnew?

功??能:?创建一个新文件?

用??法:?int?creatnew(const?char?*filename,?int?attrib);?

程序例:?

#include?<string.h>?
#include?<stdio.h>?
#include?<errno.h>?
#include?<dos.h>?
#include?<io.h>?
int?main(void)?
{?
???int?handle;?
???char?buf[11]?=?"0123456789";?
???/*?attempt?to?create?a?file?that?doesn‘t?already?exist?*/?
???handle?=?creatnew("DUMMY.FIL",?0);?
???if?(handle?==?-1)?
??????printf("DUMMY.FIL?already?exists.\n");?
???else?
???{?
??????printf("DUMMY.FIL?successfully?created.\n");?
??????write(handle,?buf,?strlen(buf));?
??????close(handle);?
???}?
???return?0;?
}?
??
??
??

函数名:?creattemp?

功??能:?创建一个新文件或重写一个已存在的文件?

用??法:?int?creattemp(const?char?*filename,?int?attrib);?

程序例:?

#include?<string.h>?
#include?<stdio.h>?
#include?<io.h>?
int?main(void)?
{?
???int?handle;?
???char?pathname[128];?
???strcpy(pathname,?"\\");?
???/*?create?a?unique?file?in?the?root?directory?*/?
???handle?=?creattemp(pathname,?0);?
???printf("%s?was?the?unique?file?created.\n",?pathname);?
???close(handle);?
???return?0;?
}?
??
??
??

函数名:?cscanf?

功??能:?从控制台执行格式化输入?

用??法:?int?cscanf(char?*format[,argument,?...]);?

程序例:?

#include?<conio.h>?
int?main(void)?
{?
???char?string[80];?
???/*?clear?the?screen?*/?
???clrscr();?
???/*?Prompt?the?user?for?input?*/?
???cprintf("Enter?a?string?with?no?spaces:");?
???/*?read?the?input?*/?
???cscanf("%s",?string);?
???/*?display?what?was?read?*/?
???cprintf("\r\nThe?string?entered?is:?%s",?string);?
???return?0;?
}?
??
??
??

函数名:?ctime?

功??能:?把日期和时间转换为字符串?

用??法:?char?*ctime(const?time_t?*time);?

程序例:?

#include?<stdio.h>?
#include?<time.h>?
int?main(void)?
{?
???time_t?t;?
???time(&t);?
???printf("Today‘s?date?and?time:?%s\n",?ctime(&t));?
???return?0;?
}?
??
??
??

函数名:?ctrlbrk?

功??能:?设置Ctrl-Break处理程序?

用??法:?void?ctrlbrk(*fptr)(void);?

程序例:?

#include?<stdio.h>?
#include?<dos.h>?
#define?ABORT?0?
int?c_break(void)?
{?
???printf("Control-Break?pressed.??Program?aborting?...\n");?
???return?(ABORT);?
}?
int?main(void)?
{?
???ctrlbrk(c_break);?
???for(;;)?
???{?
??????printf("Looping...?Press?<Ctrl-Break>?to?quit:\n");?
???}?
???return?0;?
}?
??
??
??
??