功能名称: abort

动力 能够: 异常终止的过程的

使用 法国: void abort(void);

程序示例:

#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: 确定文件的訪问权限

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: 測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: 注冊终止函数

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);

} 

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