C语言库函数(O类字母)

函数名: open
功  能: 打开一个文件用于读或写
用  法: int open(char *pathname, int Access[, int permiss]);
程序例:
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>

int main(void)
{
   int handle;
   char msg[] = "Hello world";

   if ((handle = open("TEST.$$$", O_CREAT  O_TEXT)) == -1)
   {
      perror("Error:");
      return 1;
   }
   write(handle, msg, strlen(msg));
   close(handle);
   return 0;
}



函数名: outport
功  能: 输出整数到硬件端口中
用  法: void outport(int port, int value);
程序例:

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

int main(void)
{
   int value = 64;
   int port = 0;

   outportb(port, value);
   printf("Value %d sent to port number %d\n", value, port);
   return 0;
}



函数名: outportb
功  能: 输出字节到硬件端口中
用  法: void outportb(int port, char byte);
程序例:

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

int main(void)
{
   int value = 64;
   int port = 0;

   outportb(port, value);
   printf("Value %d sent to port number %d\n", value, port);
   return 0;
}



函数名: outtext
功  能: 在视区显示一个字符串
用  法: void far outtext(char far *textstring);
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;

   /* move the C.P. to the center of the screen */
   moveto(midx, midy);

   /* output text starting at the C.P. */
   outtext("This ");
   outtext("is ");
   outtext("a ");
   outtext("test.");

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



函数名: outtextxy
功  能: 在指定位置显示一字符串
用  法: void far outtextxy(int x, int y, char *textstring);
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;

   /* output text at the center of the screen*/
   /* Note: the C.P. doesn't get changed.*/
   outtextxy(midx, midy, "This is a test.");

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