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Turbo C 2.0、Borland C++库函数及用例(12) }
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()
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