c.txt

c语言函数以及它的相关只是的学习

   }
   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;
}