C语言函数_D起始_C语言教程

C语言函数_D起始_C语言教程

函数名: delay          
功  能: 将程序的执行暂停一段时间(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;
}
 
 

函数名: delline
功  能: 在文本窗口中删去一行
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;
}
 

函数名: detectgraph
功  能: 通过检测硬件确定图形驱动程序和模式
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;
}
 
 
 

函数名: difftime
功  能: 计算两个时刻之间的时间差
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;
}
 
 

函数名: disable
功  能: 屏蔽中断
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;
}

函数名: div
功  能: 将两个整数相除, 返回商和余数
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;
}
 
 

函数名: dosexterr
功  能: 获取扩展DOS错误信息
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;
}
 
 

函数名: dostounix
功  能: 转换日期和时间为UNIX时间格式
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;
}
 
 

函数名: drawpoly
功  能: 画多边形
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;
}
 
 

函数名: dup
功  能: 复制一个文件句柄
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();
   return 0;
}

void flush(FILE *stream)
{
   int duphandle;

   /* flush TC's internal buffer */
   fflush(stream);

   /* make a duplicate file handle */
   duphandle = dup(fileno(stream));

   /* close the duplicate handle to flush the
      DOS buffer */
   close(duphandle);
}
 
 

函数名: dup2
功  能: 复制文件句柄
用  法: int dup2(int oldhandle, int newhandle);
程序例:

#include <sys\stat.h>
#include <string.h>
#include <fcntl.h>
#include <io.h>

int main(void)
{
   #define STDOUT 1

   int nul, oldstdout;
   char msg[] = "This is a test";

   /* create a file */
   nul = open("DUMMY.FIL", O_CREAT | O_RDWR,
      S_IREAD | S_IWRITE);

   /* create a duplicate handle for standard
      output */
   oldstdout = dup(STDOUT);
   /*
      redirect standard output to DUMMY.FIL
      by duplicating the file handle onto the
      file handle for standard output.
   */
   dup2(nul, STDOUT);

   /* close the handle for DUMMY.FIL */
   close(nul);

   /* will be redirected into DUMMY.FIL */
   write(STDOUT, msg, strlen(msg));

   /* restore original standard output
      handle */
   dup2(oldstdout, STDOUT);

   /* close duplicate handle for STDOUT */
   close(oldstdout);

   return 0;
}

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