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;
}
函數名: 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;
}
函數名: 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;
}
函數名: coreleft
功  能: 返回未使用內存的大小
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;
}
函數名: cos
功  能: 余弦函數
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;
}
函數名: cosh
功  能: 雙曲余弦函數
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;
}
函數名: country
功  能: 返回與國家有關的信息
用  法: struct COUNTRY *country( int countrycode,
				 struct country *country);
程序例:#include <dos.h>
#include <stdio.h>#define USA 0int 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;
}
函數名: cprintf
功  能: 送格式化輸出至屏幕
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;
}
函數名: cputs
功  能: 寫字符到屏幕
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;
}
函數名: _creat, creat
功  能: 創建一個新文件或重寫一個已存在的文件
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;
}
函數名: creatnew
功  能: 創建一個新文件
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;
}
函數名: creattemp
功  能: 創建一個新文件或重寫一個已存在的文件
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;
}
函數名: cscanf
功  能: 從控制臺執行格式化輸入
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;
}
函數名: ctime
功  能: 把日期和時間轉換為字符串
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;
}
函數名: ctrlbrk
功  能: 設置Ctrl-Break處理程序
用  法: void ctrlbrk(*fptr)(void);
程序例:#include <stdio.h>
#include <dos.h>#define ABORT 0int 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;
}字母Ｄ開頭函數
函數名: delay
功  能: 將程序的執行暫停一段時間(毫秒)
用  法: void delay(unsigned milliseconds);
程序例:
/* Emits a 440-Hz tone for 500 milliseconds */
#include <dos.h>int main(void)
{
   sound(440);
   delay(500);
   nosound();
   return 0;
}
函數名: delline
功  能: 在文本窗口中刪去一行
用  法: void delline(void);
程序例:#include <conio.h>int main(void)
{
   clrscr();
   cprintf("The function DELLINE deletes \
	 the line containing the\r\n");
   cprintf("cursor and moves all lines \
	 below it one line up.\r\n");   cprintf("DELLINE operates within the \
	 currently active text\r\n");
   cprintf("window.  Press any key to \
	 continue . . .");
   gotoxy(1,2);  /* Move the cursor to the
      second line and first column */
   getch();
   delline();
   getch();   return 0;
}
函數名: detectgraph
功  能: 通過檢測硬件確定圖形驅動程序和模式
用  法: void far detectgraph( int far *graphdriver,
			      int far *graphmode);
程序例:#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>/* names of the various cards supported */
char *dname[] = { "requests detection",
	      "a CGA",	      "an MCGA",
	      "an EGA",
	      "a 64K EGA",
	      "a monochrome EGA",
	      "an IBM 8514",
	      "a Hercules monochrome",
	      "an AT&T 6300 PC",
	      "a VGA",
	      "an IBM 3270 PC"
	    };int main(void)
{
   /* returns detected hardware info. */   int gdriver, gmode, errorcode;  /* detect graphics hardware available */
   detectgraph(&gdriver, &gmode);   /* read result of detectgraph call */
   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 */
   }   /* display the information detected */
   clrscr();
   printf("You have %s video display \
	card.\n", dname[gdriver]);
   printf("Press any key to halt:");
   getch();
   return 0;
}
函數名: difftime
功  能: 計算兩個時刻之間的時間差
用  法: double difftime(time_t time2, time_t time1);
程序例:#include <time.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>int main(void)
{
   time_t first, second;
   clrscr();
   first = time(NULL);  /* Gets system time */   delay(2000);         /* Waits 2 secs */
   second = time(NULL); /* Gets system time
		     again */
   printf("The difference is: %f \
	seconds\n",difftime(second,first));
   getch();
   return 0;
}
函數名: disable
功  能: 屏蔽中斷
用  法: void disable(void);
程序例:/***NOTE: This is an interrupt service
 routine. You cannot compile this program
 with Test Stack Overflow turned on and
 get an executable file that operates
 correctly. */#include <stdio.h>
#include <dos.h>
#include <conio.h>#define INTR 0X1C    /* The clock tick interrupt */void interrupt ( *oldhandler)(void);int count=0;void interrupt handler(void)
{
/* disable interrupts during the handling of
   the interrupt */
   disable();
/* increase the global counter */
   count++;/* reenable interrupts at the end of the
   handler */
   enable();
/* call the old routine */
   oldhandler();
}int main(void)
{
/* save the old interrupt vector */
   oldhandler = getvect(INTR);/* install the new interrupt handler */
   setvect(INTR, handler);/* loop until the counter exceeds 20 */
   while (count < 20)
      printf("count is %d\n",count);/* reset the old interrupt handler */
   setvect(INTR, oldhandler);   return 0;
}
函數名: div
功  能: 將兩個整數相除, 返回商和余數
用  法: div_t (int number, int denom);
程序例:
#include <stdlib.h>
#include <stdio.h>
div_t x;int main(void)
{
   x = div(10,3);
   printf("10 div 3 = %d remainder %d\n", x.quot, x.rem);
   return 0;
}
函數名: dosexterr
功  能: 獲取擴展DOS錯誤信息
用  法: int dosexterr(struct DOSERR *dblkp);
程序例:#include <stdio.h>
#include <dos.h>int main(void)
{
   FILE *fp;
   struct DOSERROR info;   fp = fopen("perror.dat","r");   if (!fp) perror("Unable to open file for
	       reading");
   dosexterr(&info);   printf("Extended DOS error \
	information:\n");
   printf("   Extended error: \
	%d\n",info.exterror);
   printf("            Class: \
	%x\n",info.class);
   printf("           Action: \
	%x\n",info.action);
   printf("      Error Locus: \
	%x\n",info.locus);   return 0;
}
函數名: dostounix
功  能: 轉換日期和時間為UNIX時間格式
用  法: long dostounix( struct date *dateptr,
			struct time *timeptr );
程序例: #include <time.h>
 #include <stddef.h>
 #include <dos.h>
 #include <stdio.h> int main(void)
 {
    time_t t;    struct time d_time;
    struct date d_date;
    struct tm *local;    getdate(&d_date);
    gettime(&d_time);    t = dostounix(&d_date, &d_time);
    local = localtime(&t);
    printf("Time and Date: %s\n", asctime(local));
    return 0;
}
函數名: drawpoly
功  能: 畫多邊形
用  法: void far drawpoly( int numpoints,
			   int far *polypoints );
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 maxx, maxy;   /* our polygon array */
   int poly[10];   /* 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();
   /* terminate with an error code */
      exit(1);
   }
   maxx = getmaxx();
   maxy = getmaxy();   poly[0] = 20;        /* 1st vertext */
   poly[1] = maxy / 2;   poly[2] = maxx - 20; /* 2nd */
   poly[3] = 20;   poly[4] = maxx - 50; /* 3rd */
   poly[5] = maxy - 20;   poly[6] = maxx / 2;  /* 4th */
   poly[7] = maxy / 2;
/*
   drawpoly doesn't automatically close
   the polygon, so we close it.
*/   poly[8] = poly[0];
   poly[9] = poly[1];   /* draw the polygon */
   drawpoly(5, poly);   /* clean up */
   getch();
   closegraph();
   return 0;
}
函數名: dup
功  能: 復制一個文件句柄
用  法: int dup(int handle);
程序例:#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <io.h>void flush(FILE *stream);int main(void)
{   FILE *fp;
   char msg[] = "This is a test";   /* create a file */
   fp = fopen("DUMMY.FIL", "w");   /* write some data to the file */
   fwrite(msg, strlen(msg), 1, fp);
   clrscr();
   printf("Press any key to flush \
	DUMMY.FIL:");
   getch();   /* flush the data to DUMMY.FIL without
      closing it */
   flush(fp);   printf("\nFile was flushed, Press any \
	key to quit:");
   getch();