C语言库函数大全及应用实例九

函数名: modf
功 能: 把数分为指数和尾数
用 法: double modf(double value, double *iptr);
程序例:

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int main(void)
{
double fraction, integer;
double number = 100000.567;

fraction = modf(number, &integer);
printf("The whole and fractional parts of %lf are %lf and %lf\n",
number, integer, fraction);
return 0;
}

函数名: movedata
功 能: 拷贝字节
用 法: void movedata(int segsrc, int offsrc, int segdest,
int offdest, unsigned numbytes);
程序例:

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#define MONO_BASE 0xB000

/* saves the contents of the monochrome screen in buffer */
void save_mono_screen(char near *buffer)
{
movedata(MONO_BASE, 0, _DS, (unsigned)buffer, 80*25*2);
}

int main(void)
{
char buf[80*25*2];
save_mono_screen(buf);
}

函数名: moverel
功 能: 将当前位置(CP)移动一相对距离
用 法: void far moverel(int dx, int dy);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
char msg[80];

/* 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 */
}

/* move the C.P. to location (20, 30) */
moveto(20, 30);

/* plot a pixel at the C.P. */
putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at (20, 30) */
sprintf(msg, " (%d, %d)", getx(), gety());
outtextxy(20, 30, msg);

/* move to a point a relative distance */
/* away from the current value of C.P. */
moverel(100, 100);

/* plot a pixel at the C.P. */
putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at C.P. */
sprintf(msg, " (%d, %d)", getx(), gety());
outtext(msg);

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

函数名: movetext
功 能: 将屏幕文本从一个矩形区域拷贝到另一个矩形区域
用 法: int movetext(int left, int top, int right, int bottom,
int newleft, int newtop);
程序例:
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int main(void)
{
char *str = "This is a test string";

clrscr();
cputs(str);
getch();

movetext(1, 1, strlen(str), 2, 10, 10);
getch();

return 0;
}

函数名: moveto
功 能: 将CP移到(x, y)
用 法: void far moveto(int x, int y);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
char msg[80];

/* 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 */
}

/* move the C.P. to location (20, 30) */
moveto(20, 30);

/* plot a pixel at the C.P. */
putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at (20, 30) */
sprintf(msg, " (%d, %d)", getx(), gety());
outtextxy(20, 30, msg);

/* move to (100, 100) */
moveto(100, 100);

/* plot a pixel at the C.P. */
putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at C.P. */
sprintf(msg, " (%d, %d)", getx(), gety());
outtext(msg);

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

函数名: movemem
功 能: 移动一块字节
用 法: void movemem(void *source, void *destin, unsigned len);
程序例:

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int main(void)
{
char *source = "Borland International";
char *destination;
int length;

length = strlen(source);
destination = malloc(length + 1);
movmem(source,destination,length);
printf("%s\n",destination);

return 0;
}

函数名: normvideo
功 能: 选择正常亮度字符
用 法: void normvideo(void);
程序例:

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int main(void)
{
normvideo();
cprintf("NORMAL Intensity Text\r\n");
return 0;
}

函数名: nosound
功 能: 关闭PC扬声器
用 法: void nosound(void);
程序例:

/* Emits a 7-Hz tone for 10 seconds.

True story: 7 Hz is the resonant frequency of a chicken's skull cavity.
This was determined empirically in Australia, where a new factory
generating 7-Hz tones was located too close to a chicken ranch:
When the factory started up, all the chickens died.

Your PC may not be able to emit a 7-Hz tone.
*/

int main(void)
{
sound(7);
delay(10000);
nosound();
}

void normvideo(void );
选择正常亮度字符。
将文本属性（前景和背景）置为启动程序时它所具有的值，来选择标准字符。

void nosound(void );
关闭由调用 sound而发声的扬声器。

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:

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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:

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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:

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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:

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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:

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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;
}

函数名: parsfnm
功 能: 分析文件名
用 法: char *parsfnm (char *cmdline, struct fcb *fcbptr, int option);
程序例:

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int main(void)
{
char line[80];
struct fcb blk;

/* get file name */
printf("Enter drive and file name (no path - ie. a:file.dat)\n");
gets(line);

/* put file name in fcb */
if (parsfnm(line, &blk, 1) == NULL)
printf("Error in parsfm call\n");
else
printf("Drive #%d Name: %11s\n", blk.fcb_drive, blk.fcb_name);

return 0;
}

函数名: peek
功 能: 检查存储单元
用 法: int peek(int segment, unsigned offset);
程序例:

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int main(void)
{
int value = 0;

printf("The current status of your keyboard is:\n");
value = peek(0x0040, 0x0017);
if (value & 1)
printf("Right shift on\n");
else
printf("Right shift off\n");

if (value & 2)
printf("Left shift on\n");
else
printf("Left shift off\n");

if (value & 4)
printf("Control key on\n");
else
printf("Control key off\n");

if (value & 8)
printf("Alt key on\n");
else
printf("Alt key off\n");

if (value & 16)
printf("Scroll lock on\n");
else
printf("Scroll lock off\n");

if (value & 32)
printf("Num lock on\n");
else
printf("Num lock off\n");

if (value & 64)
printf("Caps lock on\n");
else
printf("Caps lock off\n");

return 0;
}

函数名: peekb
功 能: 检查存储单元
用 法: char peekb (int segment, unsigned offset);
程序例:

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int main(void)
{
int value = 0;

printf("The current status of your keyboard is:\n");
value = peekb(0x0040, 0x0017);
if (value & 1)
printf("Right shift on\n");
else
printf("Right shift off\n");

if (value & 2)
printf("Left shift on\n");
else
printf("Left shift off\n");

if (value & 4)
printf("Control key on\n");
else
printf("Control key off\n");

if (value & 8)
printf("Alt key on\n");
else
printf("Alt key off\n");

if (value & 16)
printf("Scroll lock on\n");
else
printf("Scroll lock off\n");

if (value & 32)
printf("Num lock on\n");
else
printf("Num lock off\n");

if (value & 64)
printf("Caps lock on\n");
else
printf("Caps lock off\n");

return 0;
}

函数名: perror
功 能: 系统错误信息
用 法: void perror(char *string);
程序例:

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int main(void)
{
FILE *fp;

fp = fopen("perror.dat", "r");
if (!fp)
perror("Unable to open file for reading");
return 0;
}

函数名: pieslice
功 能: 绘制并填充一个扇形
用 法: void far pieslice(int x, int stanle, int endangle, int radius);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy;
int stangle = 45, endangle = 135, 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;

/* set fill style and draw a pie slice */
setfillstyle(EMPTY_FILL, getmaxcolor());
pieslice(midx, midy, stangle, endangle, radius);

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

函数名: putch
功 能: 输出字符到控制台
用 法: int putch(int ch);
程序例:

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int main(void)
{
char ch = 0;

printf(\"Input a string:\");
while ((ch != \'\\r\'))
{
ch = getch();
putch(ch);
}
return 0;
}

函数名: putchar
功 能: 在stdout上输出字符
用 法: int putchar(int ch);
程序例:

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/* define some box-drawing characters */
#define LEFT_TOP 0xDA
#define RIGHT_TOP 0xBF
#define HORIZ 0xC4
#define VERT 0xB3
#define LEFT_BOT 0xC0
#define RIGHT_BOT 0xD9

int main(void)
{
char i, j;

/* draw the top of the box */
putchar(LEFT_TOP);
for (i=0; i<10; i++)
putchar(HORIZ);
putchar(RIGHT_TOP);
putchar(\'\\n\');

/* draw the middle */
for (i=0; i<4; i++)
{
putchar(VERT);
for (j=0; j<10; j++)
putchar(\' \');
putchar(VERT);
putchar(\'\\n\');
}

/* draw the bottom */
putchar(LEFT_BOT);
for (i=0; i<10; i++)
putchar(HORIZ);
putchar(RIGHT_BOT);
putchar(\'\\n\');

return 0;
}

函数名: putenv
功 能: 把字符串加到当前环境中
用 法: int putenv(char *envvar);
程序例:

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int main(void)
{
char *path, *ptr;
int i = 0;

/* get the current path environment */
ptr = getenv(\"PATH\");

/* set up new path */
path = malloc(strlen(ptr)+15);
strcpy(path,\"PATH=\");
strcat(path,ptr);
strcat(path,\";c:\\\\temp\");

/* replace the current path and display current environment */
putenv(path);
while (environ)
printf(\"%s\\n\",environ[i++]);