C语言函数汇总1

函数名: abort
功  能: 异常终止一个进程
用  法: void abort(void);
程序例:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
  printf("Calling abort()\n");
  abort();
  return 0; /* This is never reached */
} 
 

函数名: abs
功  能: 求整数的绝对值
用  法: int abs(int i);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
  int number = -1234;

  printf("number: %d  absolute value: %d\n", number, abs(number));
  return 0;
} 

函数名: absread, abswirte
功  能: 绝对磁盘扇区读、写数据
用  法: int absread(int drive, int nsects, int sectno, void *buffer);
 int abswrite(int drive, int nsects, in tsectno, void *buffer);
程序例:
/* absread example */
#include <stdio.h>
#include <conio.h>
#include <process.h>
#include <dos.h>
int main(void)
{
  int i, strt, ch_out, sector;
  char buf[512];
  printf("Insert a diskette into drive A and press any key\n");
  getch();
  sector = 0;
  if (absread(0, 1, sector, &buf) != 0)
  {
     perror("Disk problem");
     exit(1);
  }
  printf("Read OK\n");
  strt = 3;
  for (i=0; i<80; i++)
  {
     ch_out = 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: int access(const char *filename, int amode);
程序例:
#include <stdio.h>
#include <io.h>
int file_exists(char *filename);
int main(void)
{
  printf("Does NOTEXIST.FIL exist: %s\n",
  file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
  return 0;
}
int file_exists(char *filename)
{
  return (access(filename, 0) == 0);
} 

函数名: acos
功  能: 反余弦函数
用  法: double acos(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
  double result;
  double x = 0.5;
  result = acos(x);
  printf("The arc cosine of %lf is %lf\n", x, result);
  return 0;
} 

函数名: allocmem
功  能: 分配DOS存储段
用  法: int allocmem(unsigned size, unsigned *seg);
程序例:
#include <dos.h>
#include <alloc.h>
#include <stdio.h>
int main(void)
{
  unsigned int size, segp;
  int stat;
  size = 64; /* (64 x 16) = 1024 bytes */
  stat = allocmem(size, &segp);
  if (stat == -1)
     printf("Allocated memory at segment: %x\n", segp);
  else
     printf("Failed: maximum number of paragraphs available is %u\n",
            stat);

  return 0;
} 

函数名: arc
功  能: 画一弧线
用  法: void far arc(int x, int y, int stangle, int endangle, 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 stangle = 45, endangle = 135;
   int radius = 100;
   /* initialize graphics and local variables */
   initgraph(&gdriver, &gmode, "");
   /* read result of initialization */
   errorcode = graphresult();    /* an error occurred */
   if (errorcode != grOk)
   {
      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 arc */
   arc(midx, midy, stangle, endangle, radius);

   /* clean up */
   getch();
   closegraph();
   return 0;
} 

函数名: asctime
功  能: 转换日期和时间为ASCII码
用  法: char *asctime(const struct tm *tblock);
程序例:
#include <stdio.h>
#include <string.h>
#include <time.h>

int main(void)
{
   struct tm t;
   char str[80];

   /* sample loading of tm structure  */

   t.tm_sec    = 1;  /* Seconds */
   t.tm_min    = 30; /* Minutes */
   t.tm_hour   = 9;  /* Hour */
   t.tm_mday   = 22; /* Day of the Month  */
   t.tm_mon    = 11; /* Month */
   t.tm_year   = 56; /* Year - does not include century */
   t.tm_wday   = 4;  /* Day of the week  */
   t.tm_yday   = 0;  /* Does not show in asctime  */
   t.tm_isdst  = 0;  /* Is Daylight SavTime; does not show in asctime */

   /* converts structure to null terminated
   string */

   strcpy(str, asctime(&t));
   printf("%s\n", str);

   return 0;
} 

函数名: asin
功  能: 反正弦函数
用  法: double asin(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
   double result;
   double x = 0.5;

   result = asin(x);
   printf("The arc sin of %lf is %lf\n", 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: void assert(int test);
程序例:
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

struct ITEM {
   int key;
   int value;
};

/* add item to list, make sure list is not null */
void additem(struct ITEM *itemptr) {
   assert(itemptr != NULL);
   /* add item to list */
}

int main(void)
{
   additem(NULL);
   return 0;
} 

函数名: atan
功  能: 反正切函数
用  法: double atan(double x);
程序例:
#include <stdio.h>
#include <math.h>

int main(void)
{
   double result;
   double x = 0.5;

   result = atan(x);
   printf("The arc tangent of %lf is %lf\n", x, result);
   return(0);
} 

函数名: atan2
功  能: 计算Y/X的反正切值
用  法: double atan2(double y, double x);
程序例:
#include <stdio.h>
#include <math.h>

int main(void)
{
   double result;
   double x = 90.0, y = 45.0;

   result = atan2(y, x);
   printf("The arc tangent ratio of %lf is %lf\n", (y / x), result);
   return 0;
} 

函数名: atexit
功  能: 注册终止函数
用  法: int atexit(atexit_t func);
程序例:
#include <stdio.h>
#include <stdlib.h>

void exit_fn1(void)
{
   printf("Exit function #1 called\n");
}

void exit_fn2(void)
{
   printf("Exit function #2 called\n");
}

int main(void)
{
   /* post exit function #1 */
   atexit(exit_fn1);
   /* post exit function #2 */
   atexit(exit_fn2);
   return 0;
} 

函数名: atof
功  能: 把字符串转换成浮点数
用  法: double atof(const char *nptr);
程序例:
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
   float f;
   char *str = "12345.67";

   f = atof(str);
   printf("string = %s float = %f\n", str, f);
   return 0;
}
 

函数名: atoi
功  能: 把字符串转换成长整型数
用  法: int atoi(const char *nptr);
程序例:
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
   int n;
   char *str = "12345.67";

   n = atoi(str);
   printf("string = %s integer = %d\n", str, n);
   return 0;
} 

函数名: atol
功  能: 把字符串转换成长整型数
用  法: long atol(const char *nptr);
程序例:

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
   long l;
   char *str = "98765432";

   l = atol(lstr);
   printf("string = %s integer = %ld\n", str, l);
   return(0);
}

函数名: bar
功  能: 画一个二维条形图
用  法: void far bar(int left, int top, int right, int bottom);
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, i;

   /* 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;

   /* loop through the fill patterns */
   for (i=SOLID_FILL; i<USER_FILL; i++)
   {
      /* set the fill style */
      setfillstyle(i, getmaxcolor());

      /* draw the bar */
      bar(midx-50, midy-50, midx+50,
         midy+50);

      getch();
   }

   /* clean up */
   closegraph();
   return 0;
}
 
 
 

函数名: bar3d
功  能: 画一个三维条形图
用  法: void far bar3d(int left, int top, int right, int bottom,
                       int depth, int topflag);
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, i;

   /* initialize graphics, 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 error code */
   }

   midx = getmaxx() / 2;
   midy = getmaxy() / 2;

   /* loop through the fill patterns */
   for (i=EMPTY_FILL; i<USER_FILL; i++)
   {
      /* set the fill style */
      setfillstyle(i, getmaxcolor());

      /* draw the 3-d bar */
      bar3d(midx-50, midy-50, midx+50, midy+50, 10, 1);

      getch();
   }

   /* clean up */
   closegraph();
   return 0;
}
 
 
 

函数名: bdos
功  能: DOS系统调用
用  法: int bdos(int dosfun, unsigned dosdx, unsigned dosal);
程序例:

#include <stdio.h>
#include <dos.h>

/* Get current drive as 'A', 'B', ... */
char current_drive(void)
{
   char curdrive;

   /* Get current disk as 0, 1, ... */
   curdrive = bdos(0x19, 0, 0);
   return('A' + curdrive);
}

int main(void)
{
   printf("The current drive is %c:\n", current_drive());
   return 0;
}
 
 
 

函数名: bdosptr
功  能: DOS系统调用
用  法: int bdosptr(int dosfun, void *argument, unsigned dosal);
程序例:

#include <string.h>
#include <stdio.h>
#include <dir.h>
#include <dos.h>
#include <errno.h>
#include <stdlib.h>

#define  BUFLEN  80

int main(void)
{
   char  buffer[BUFLEN];
   int   test;

   printf("Enter full pathname of a directory\n");
   gets(buffer);

   test = bdosptr(0x3B,buffer,0);
      if(test)
      {
  printf("DOS error message: %d\n", errno);
  /* See errno.h for error listings */
  exit (1);
      }

   getcwd(buffer, BUFLEN);
   printf("The current directory is: %s\n", buffer);

   return 0;
}
 
 
 

函数名: bioscom
功  能: 串行I/O通信
用  法: int bioscom(int cmd, char abyte, int port);
程序例:

#include <bios.h>
#include <conio.h>

#define COM1       0
#define DATA_READY 0x100
#define TRUE       1
#define FALSE      0

#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)

int main(void)
{
   int in, out, status, DONE = FALSE;

   bioscom(0, SETTINGS, COM1);
   cprintf("... BIOSCOM [ESC] to exit ...\n");
   while (!DONE)
   {
      status = bioscom(3, 0, COM1);
      if (status & DATA_READY)
  if ((out = bioscom(2, 0, COM1) & 0x7F) != 0)
     putch(out);
  if (kbhit())
  {
     if ((in = getch()) == '\x1B')
        DONE = TRUE;
     bioscom(1, in, COM1);
  }
   }
   return 0;
}
 
 
 

函数名: biosdisk
功  能: 软硬盘I/O
用  法: int biosdisk(int cmd, int drive, int head, int track, int sector
       int nsects, void *buffer);
程序例:

#include <bios.h>
#include <stdio.h>

int main(void)
{
   int result;
   char buffer[512];

   printf("Testing to see if drive a: is ready\n");
   result = biosdisk(4,0,0,0,0,1,buffer);
   result &= 0x02;
   (result) ? (printf("Drive A: Ready\n")) :
       (printf("Drive A: Not Ready\n"));

   return 0;
}
 
 
 

函数名: biosequip
功  能: 检查设备
用  法: int biosequip(void);
程序例:

#include <bios.h>
#include <stdio.h>

int main(void)
{
   int result;
   char buffer[512];

   printf("Testing to see if drive a: is ready\n");
   result = biosdisk(4,0,0,0,0,1,buffer);
   result &= 0x02;
   (result) ? (printf("Drive A: Ready\n")) :
       (printf("Drive A: Not Ready\n"));

   return 0;
}
 
 
 

函数名: bioskey
功  能: 直接使用BIOS服务的键盘接口
用  法: int bioskey(int cmd);
程序例:

#include <stdio.h>
#include <bios.h>
#include <ctype.h>

#define RIGHT  0x01
#define LEFT   0x02
#define CTRL   0x04
#define ALT    0x08

int main(void)
{
   int key, modifiers;

   /* function 1 returns 0 until a key is pressed */
   while (bioskey(1) == 0);

   /* function 0 returns the key that is waiting */
   key = bioskey(0);

   /* use function 2 to determine if shift keys were used */
   modifiers = bioskey(2);
   if (modifiers)
   {
      printf("[");
      if (modifiers & RIGHT) printf("RIGHT");
      if (modifiers & LEFT)  printf("LEFT");
      if (modifiers & CTRL)  printf("CTRL");
      if (modifiers & ALT)   printf("ALT");
      printf("]");
   }
   /* print out the character read */
   if (isalnum(key & 0xFF))
      printf("'%c'\n", key);
   else
      printf("%#02x\n", key);
   return 0;
}
 
 

函数名: biosmemory
功  能: 返回存储块大小
用  法:int biosmemory(void);
程序例:

#include <stdio.h>
#include <bios.h>

int main(void)
{
   int memory_size;

   memory_size = biosmemory();  /* returns value up to 640K */
   printf("RAM size = %dK\n",memory_size);
   return 0;
}
 
 
 

函数名: biosprint
功  能: 直接使用BIOS服务的打印机I/O
用  法: int biosprint(int cmd, int byte, int port);
程序例:

#include <stdio.h>
#include <conio.h>
#include <bios.h>

int main(void)
{
   #define STATUS  2    /* printer status command */
   #define PORTNUM 0    /* port number for LPT1 */

   int status, abyte=0;

   printf("Please turn off your printer.  Press any key to continue\n");
   getch();
   status = biosprint(STATUS, abyte, PORTNUM);
   if (status & 0x01)
      printf("Device time out.\n");
   if (status & 0x08)
      printf("I/O error.\n");

   if (status & 0x10)
      printf("Selected.\n");
   if (status & 0x20)
      printf("Out of paper.\n");

   if (status & 0x40)
      printf("Acknowledge.\n");
   if (status & 0x80)
      printf("Not busy.\n");

   return 0;
}
 
 
 

函数名: biostime
功  能: 读取或设置BIOS时间
用  法: long biostime(int cmd, long newtime);
程序例:

#include <stdio.h>
#include <bios.h>
#include <time.h>
#include <conio.h>

int main(void)
{
   long bios_time;

   clrscr();
   cprintf("The number of clock ticks since midnight is:\r\n");
   cprintf("The number of seconds since midnight is:\r\n");
   cprintf("The number of minutes since midnight is:\r\n");
   cprintf("The number of hours since midnight is:\r\n");
   cprintf("\r\nPress any key to quit:");
   while(!kbhit())
   {
      bios_time = biostime(0, 0L);

      gotoxy(50, 1);
      cprintf("%lu", bios_time);

      gotoxy(50, 2);
      cprintf("%.4f", bios_time / CLK_TCK);

      gotoxy(50, 3);
      cprintf("%.4f", bios_time / CLK_TCK / 60);

      gotoxy(50, 4);
      cprintf("%.4f", bios_time / CLK_TCK / 3600);
   }
   return 0;
}
 
 
 

函数名: brk
功  能: 改变数据段空间分配
用  法: int brk(void *endds);
程序例:

#include <stdio.h>
#include <alloc.h>

int main(void)
{
   char *ptr;

   printf("Changing allocation with brk()\n");
   ptr = malloc(1);
   printf("Before brk() call: %lu bytes free\n", coreleft());
   brk(ptr+1000);
   printf(" After brk() call: %lu bytes free\n", coreleft());
   return 0;
}
 
 
 

函数名: bsearch
功  能: 二分法搜索
用  法: void *bsearch(const void *key, const void *base, size_t *nelem,  size_t width, int(*fcmp)(const void *, const *));
程序例:

#include <stdlib.h>
#include <stdio.h>

#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))

int numarray[] = {123, 145, 512, 627, 800, 933};

int numeric (const int *p1, const int *p2)
{
   return(*p1 - *p2);
}

int lookup(int key)
{
   int *itemptr;

   /* The cast of (int(*)(const void *,const void*))
      is needed to avoid a type mismatch error at
      compile time */
   itemptr = bsearch (&key, numarray, NELEMS(numarray),
      sizeof(int), (int(*)(const void *,const void *))numeric);
   return (itemptr != NULL);
}

int main(void)
{
   if (lookup(512))
      printf("512 is in the table.\n");
   else
      printf("512 isn't in the table.\n");

   return 0;
}

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;
}