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C语言库函数 (C类字母)

2008-06-01 02:09:01  編輯來源:互聯網  简体版  手機版  評論  字體: ||
 
 
  [ 发表日期:2002-1-4 9:28:46 ]

  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;

  }
 
 
 
  [ 发表日期:2002-1-4 9:28:46 ] 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; }
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