C语言库函数大全及应用实例二

原文:C语言库函数大全及应用实例二

                                             [编程资料]C语言库函数大全及应用实例二

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#define RIGHT 0x01
#define LEFT 0x02
#define CTRL 0x04
#define ALT 0x08

int main(void)
{
int key, modifiers;

/* function 1 returns 0 until a key is pressed */
while (bioskey(1) == 0);

/* function 0 returns the key that is waiting */
key = bioskey(0);

/* use function 2 to determine if shift keys were used */
modifiers = bioskey(2);
if (modifiers)
{
printf("[");
if (modifiers & RIGHT) printf("RIGHT");
if (modifiers & LEFT) printf("LEFT");
if (modifiers & CTRL) printf("CTRL");
if (modifiers & ALT) printf("ALT");
printf("]");
}
/* print out the character read */
if (isalnum(key & 0xFF))
printf("'%c'\n", key);
else
printf("%#02x\n", key);
return 0;
}

函数名: biosmemory
功 能: 返回存储块大小
用 法:int biosmemory(void);
程序例:

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int main(void)
{
int memory_size;

memory_size = biosmemory(); /* returns value up to 640K */
printf("RAM size = %dK\n",memory_size);
return 0;
}

函数名: biosprint
功 能: 直接使用BIOS服务的打印机I/O
用 法: int biosprint(int cmd, int byte, int port);
程序例:

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int main(void)
{
#define STATUS 2 /* printer status command */
#define PORTNUM 0 /* port number for LPT1 */

int status, abyte=0;

printf("Please turn off your printer. Press any key to continue\n");
getch();
status = biosprint(STATUS, abyte, PORTNUM);
if (status & 0x01)
printf("Device time out.\n");
if (status & 0x08)
printf("I/O error.\n");

if (status & 0x10)
printf("Selected.\n");
if (status & 0x20)
printf("Out of paper.\n");

if (status & 0x40)
printf("Acknowledge.\n");
if (status & 0x80)
printf("Not busy.\n");

return 0;
}

函数名: biostime
功 能: 读取或设置BIOS时间
用 法: long biostime(int cmd, long newtime);
程序例:

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int main(void)
{
long bios_time;

clrscr();
cprintf("The number of clock ticks since midnight is:\r\n");
cprintf("The number of seconds since midnight is:\r\n");
cprintf("The number of minutes since midnight is:\r\n");
cprintf("The number of hours since midnight is:\r\n");
cprintf("\r\nPress any key to quit:");
while(!kbhit())
{
bios_time = biostime(0, 0L);

gotoxy(50, 1);
cprintf("%lu", bios_time);

gotoxy(50, 2);
cprintf("%.4f", bios_time / CLK_TCK);

gotoxy(50, 3);
cprintf("%.4f", bios_time / CLK_TCK / 60);

gotoxy(50, 4);
cprintf("%.4f", bios_time / CLK_TCK / 3600);
}
return 0;
}

函数名: brk
功 能: 改变数据段空间分配
用 法: int brk(void *endds);
程序例:

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int main(void)
{
char *ptr;

printf("Changing allocation with brk()\n");
ptr = malloc(1);
printf("Before brk() call: %lu bytes free\n", coreleft());
brk(ptr+1000);
printf(" After brk() call: %lu bytes free\n", coreleft());
return 0;
}

函数名: bsearch
功 能: 二分法搜索
用 法: void *bsearch(const void *key, const void *base, size_t *nelem,
size_t width, int(*fcmp)(const void *, const *));
程序例:

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#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))

int numarray[] = {123, 145, 512, 627, 800, 933};

int numeric (const int *p1, const int *p2)
{
return(*p1 - *p2);
}

int lookup(int key)
{
int *itemptr;

/* The cast of (int(*)(const void *,const void*))
is needed to avoid a type mismatch error at
compile time */
itemptr = bsearch (&key, numarray, NELEMS(numarray),
sizeof(int), (int(*)(const void *,const void *))numeric);
return (itemptr != NULL);
}

int main(void)
{
if (lookup(512))
printf("512 is in the table.\n");
else
printf("512 isn't in the table.\n");

return 0;
}

函数名: cabs
功 能: 计算复数的绝对值
用 法: double cabs(struct complex z);
程序例:

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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:

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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:

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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:

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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:

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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:

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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:

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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:

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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:

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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;
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:

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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:

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#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:

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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:

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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:

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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:

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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:

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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:

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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:

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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:

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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:

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#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:

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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:

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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:

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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:

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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:

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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:

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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:

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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:

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#define ABORT 0

int c_b