标题: 常用C语言库函数 [打印本页]
作者: starlight 时间: 2005-5-9 01:36 标题: 常用C语言库函数
函数名: abort
功 能: 异常终止一个进程
用 法: void abort(void);
程序例:
#include
#include
int main(void)
{
printf("Calling abort()\n");
abort();
return 0; /* This is never reached */
}
函数名: abs
功 能: 求整数的绝对值
用 法: int abs(int i);
程序例:
#include
#include
int main(void)
{
int number = -1234;
printf("number: %d absolute value: %d\n", number, abs(number));
return 0;
}
函数名: absread, abswirte
功 能: 绝对磁盘扇区读、写数据
用 法: int absread(int drive, int nsects, int sectno, void *buffer);
int abswrite(int drive, int nsects, in tsectno, void *buffer);
程序例:
/* absread example */
#include
#include
#include
#include
int main(void)
{
int i, strt, ch_out, sector;
char buf[512];
printf("Insert a diskette into drive A and press any key\n");
getch();
sector = 0;
if (absread(0, 1, sector, &buf) != 0)
{
perror("Disk problem");
exit(1);
}
printf("Read OK\n");
strt = 3;
for (i=0; i<80; i++)
{
ch_out = buf[strt+i];
putchar(ch_out);
}
printf("\n");
return(0);
}
函数名: access
功 能: 确定文件的访问权限
用 法: int access(const char *filename, int amode);
程序例:
#include
#include
int file_exists(char *filename);
int main(void)
{
printf("Does NOTEXIST.FIL exist: %s\n",
file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
return 0;
}
int file_exists(char *filename)
{
return (access(filename, 0) == 0);
}
函数名: acos
功 能: 反余弦函数
用 法: double acos(double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 0.5;
result = acos(x);
printf("The arc cosine of %lf is %lf\n", x, result);
return 0;
}
函数名: allocmem
功 能: 分配DOS存储段
用 法: int allocmem(unsigned size, unsigned *seg);
程序例:
#include
#include
#include
int main(void)
{
unsigned int size, segp;
int stat;
size = 64; /* (64 x 16) = 1024 bytes */
stat = allocmem(size, &segp);
if (stat == -1)
printf("Allocated memory at segment: %x\n", segp);
else
printf("Failed: maximum number of paragraphs available is %u\n",
stat);
return 0;
}
函数名: arc
功 能: 画一弧线
用 法: void far arc(int x, int y, int stangle, int endangle, int radius);
程序例:
#include
#include
#include
#include
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy;
int stangle = 45, endangle = 135;
int radius = 100;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult(); /* an error occurred */
if (errorcode != grOk)
{
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 arc */
arc(midx, midy, stangle, endangle, radius);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: asctime
功 能: 转换日期和时间为ASCII码
用 法: char *asctime(const struct tm *tblock);
程序例:
#include
#include
#include
int main(void)
{
struct tm t;
char str[80];
/* sample loading of tm structure */
t.tm_sec = 1; /* Seconds */
t.tm_min = 30; /* Minutes */
t.tm_hour = 9; /* Hour */
t.tm_mday = 22; /* Day of the Month */
t.tm_mon = 11; /* Month */
t.tm_year = 56; /* Year - does not include century */
t.tm_wday = 4; /* Day of the week */
t.tm_yday = 0; /* Does not show in asctime */
t.tm_isdst = 0; /* Is Daylight SavTime; does not show in asctime */
/* converts structure to null terminated string */
strcpy(str, asctime(&t));
printf("%s\n", str);
return 0;
}
函数名: asin
功 能: 反正弦函数
用 法: double asin(double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 0.5;
result = asin(x);
printf("The arc sin of %lf is %lf\n", x, result);
return(0);
}
函数名: assert
功 能: 测试一个条件并可能使程序终止
用 法: void assert(int test);
程序例:
#include
#include
#include
struct ITEM {
int key;
int value;
};
/* add item to list, make sure list is not null */
void additem(struct ITEM *itemptr) {
assert(itemptr != NULL);
/* add item to list */
}
int main(void)
{
additem(NULL);
return 0;
}
函数名: atan
功 能: 反正切函数
用 法: double atan(double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 0.5;
result = atan(x);
printf("The arc tangent of %lf is %lf\n", x, result);
return(0);
}
函数名: atan2
功 能: 计算Y/X的反正切值
用 法: double atan2(double y, double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 90.0, y = 45.0;
result = atan2(y, x);
printf("The arc tangent ratio of %lf is %lf\n", (y / x), result);
return 0;
}
函数名: atexit
功 能: 注册终止函数
用 法: int atexit(atexit_t func);
程序例:
#include
#include
void exit_fn1(void)
{
printf("Exit function #1 called\n");
}
void exit_fn2(void)
{
printf("Exit function #2 called\n");
}
int main(void)
{
/* post exit function #1 */
atexit(exit_fn1);
/* post exit function #2 */
atexit(exit_fn2);
return 0;
}
函数名: atof
功 能: 把字符串转换成浮点数
用 法: double atof(const char *nptr);
程序例:
#include
#include
int main(void)
{
float f;
char *str = "12345.67";
f = atof(str);
printf("string = %s float = %f\n", str, f);
return 0;
}
函数名: atoi
功 能: 把字符串转换成长整型数
用 法: int atoi(const char *nptr);
程序例:
#include
#include
int main(void)
{
int n;
char *str = "12345.67";
n = atoi(str);
printf("string = %s integer = %d\n", str, n);
return 0;
}
函数名: atol
功 能: 把字符串转换成长整型数
用 法: long atol(const char *nptr);
程序例:
#include
#include
int main(void)
{
long l;
char *str = "98765432";
l = atol(lstr);
printf("string = %s integer = %ld\n", str, l);
return(0);
}
作者: starlight 时间: 2005-5-9 01:37 标题: 常用C语言库函数
函数名: bar
功 能: 画一个二维条形图
用 法: void far bar(int left, int top, int right, int bottom);
程序例:
#include
#include
#include
#include
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy, i;
/* initialize graphics and local variables */
nitgraph(&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;
/* loop through the fill patterns */
for (i=SOLID_FILL; i
#include
#include
#include
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy, i;
/* initialize graphics, 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 error code */
}
midx = getmaxx() / 2; midy = getmaxy() / 2;
/* loop through the fill patterns */
for (i=EMPTY_FILL; i
#include
/* Get current drive as ';A';, ';B';, ... */
char current_drive(void)
{
char curdrive; /* Get current disk as 0, 1, ... */
curdrive = bdos(0x19, 0, 0);
return(';A'; + curdrive);
}
int main(void)
{
printf("The current drive is %c:\n", current_drive());
return 0;
}
函数名: bdosptr
功 能: DOS系统调用
用 法:
int bdosptr(int dosfun, void *argument, unsigned dosal);
程序例:
#include
#include
#include
#include
#include
#include
#define BUFLEN 80
int main(void)
{
char buffer[BUFLEN];
int test;
printf("Enter full pathname of a directory\n");
gets(buffer);
test = bdosptr(0x3B,buffer,0);
if(test)
{
printf("DOS error message: %d\n", errno); /* See errno.h for error listings */
exit (1);
}
getcwd(buffer, BUFLEN);
printf("The current directory is: %s\n", buffer);
return 0;
}
函数名: bioscom
功 能: 串行I/O通信
用 法: int bioscom(int cmd, char abyte, int port);
程序例:
#include
#include
#define COM1 0
#define DATA_READY 0x100
#define TRUE 1
#define FALSE 0
#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)
int main(void)
{
int in, out, status, DONE = FALSE;
bioscom(0, SETTINGS, COM1);
cprintf("... BIOSCOM [ESC] to exit ...\n");
while (!DONE)
{
status = bioscom(3, 0, COM1);
if (status & DATA_READY)
if ((out = bioscom(2, 0, COM1) & 0x7F) != 0)
putch(out);
if (kbhit())
{
if ((in = getch()) == ';\x1B';)
DONE = TRUE;
bioscom(1, in, COM1);
}
}
return 0;
}
函数名: biosdisk
功 能: 软硬盘I/O
用 法: int biosdisk(int cmd, int drive, int head, int track, int sector int nsects, void *buffer);
程序例:
#include
#include
int main(void)
{
int result;
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) : (printf("Drive A: Not Ready\n"));
return 0;
}
函数名: biosequip
功 能: 检查设备
用 法: int biosequip(void);
程序例:
#include
#include
int main(void)
{
int result;
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) : (printf("Drive A: Not Ready\n"));
return 0;
}
函数名: bioskey
功 能: 直接使用BIOS服务的键盘接口
用 法: int bioskey(int cmd);
程序例:
#include
#include
#include
#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:
#include
#include i
nt 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:
#include
#include
#include
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:
#include
#include
#include
#include
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:
#include
#include
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:
#include
#include
#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;
}
作者: starlight 时间: 2005-5-9 01:39 标题: 常用C语言库函数
函数名: cabs
功 能: 计算复数的绝对值
用 法: double cabs(struct complex z);
程序例:
#include
#include
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:
#include
#include
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:
#include
#include
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:
#include
#include
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:
#include
#include
#include
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:
#include
#include
#include
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:
#include
#include
#include
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:
#include
#include
#include
#include
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:
#include
#include
#include
#include
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:
#include
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
#include
#include
#include
#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
#include
#include
#include
int 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:
#include
#include
#include
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
#include
#include
#include
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
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
int main(void)
{
int i;
clrscr();
or (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
#include
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
#include
nt 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
#include
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
#include
#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
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
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
#include
#include
#include
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
#include
#include
#include
#include
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;
}
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
#include
#include
int main(void)
{
nt 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
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
#include
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
#include
#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 to quit:\n");
}
return 0;
}
作者: starlight 时间: 2005-5-9 01:40 标题: 常用C语言库函数
函数名: delay
功 能: 将程序的执行暂停一段时间(毫秒)
用 法: void delay(unsigned milliseconds);
程序例:
/* Emits a 440-Hz tone for 500 milliseconds */
#include
int main(void)
{
sound(440);
delay(500);
nosound();
return 0;
}
函数名: delline
功 能: 在文本窗口中删去一行
用 法: void delline(void);
程序例:
#include
int main(void)
{
clrscr();
cprintf("The function DELLINE deletes the line containing the\r\n");
cprintf("cursor and moves all lines below it one line up.\r\n");
cprintf("DELLINE operates within the currently active text\r\n");
cprintf("window. Press any key to continue . . .");
gotoxy(1,2); /* Move the cursor to the second line and first column */
getch();
delline();
getch();
return 0;
}
函数名: detectgraph
功 能: 通过检测硬件确定图形驱动程序和模式
用 法: void far detectgraph(int far *graphdriver, int far *graphmode);
程序例:
#include
#include
#include
#include
/* names of the various cards supported */
char *dname[] = { "requests detection",
"a CGA",
"an MCGA",
"an EGA",
"a 64K EGA",
"a monochrome EGA",
"an IBM 8514",
"a Hercules monochrome",
"an AT&T 6300 PC",
"a VGA",
"an IBM 3270 PC"
};
int main(void)
{
/* returns detected hardware info. */
int gdriver, gmode, errorcode;
/* detect graphics hardware available */
detectgraph(&gdriver, &gmode);
/* read result of detectgraph call */
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 */
}
/* display the information detected */
clrscr();
printf("You have %s video display \
card.\n", dname[gdriver]);
printf("Press any key to halt:");
getch();
return 0;
}
函数名: difftime
功 能: 计算两个时刻之间的时间差
用 法: double difftime(time_t time2, time_t time1);
程序例:
#include
#include
#include
#include
int main(void)
{
time_t first, second;
clrscr();
first = time(NULL); /* Gets system time */
delay(2000); /* Waits 2 secs */
second = time(NULL); /* Gets system time again */
printf("The difference is: %f \
seconds\n",difftime(second,first));
getch();
return 0;
}
函数名: disable
功 能: 屏蔽中断
用 法: void disable(void);
程序例:
/***NOTE: This is an interrupt service
routine. You cannot compile this program
with Test Stack Overflow turned on and
get an executable file that operates
correctly. */
#include
#include
#include
#define INTR 0X1C /* The clock tick interrupt */
void interrupt ( *oldhandler)(void);
int count=0;
void interrupthandler(void)
{
/* disable interrupts during the handling of the interrupt */
disable();
/* increase the global counter */
count++;
/* reenable interrupts at the end of the handler */
enable();
/* call the old routine */
oldhandler();
}
int main(void)
{
/* save the old interrupt vector */
oldhandler = getvect(INTR);
/* install the new interrupt handler */
setvect(INTR, handler);
/* loop until the counter exceeds 20 */
while (count < 20)
printf("count is %d\n",count);
/* reset the old interrupt handler */
setvect(INTR, oldhandler);
return 0;
}
函数名: div
功 能: 将两个整数相除, 返回商和余数
用 法: div_t (int number, int denom);
程序例:
#include
#include
div_t x;
int main(void)
{
x = div(10,3);
printf("10 div 3 = %d remainder %d\n", x.quot, x.rem);
return 0;
}
函数名: dosexterr
功 能: 获取扩展DOS错误信息
用 法: int dosexterr(struct DOSERR *dblkp);
程序例:
#include
#include
int main(void)
{
FILE *fp;
struct DOSERROR info;
fp = fopen("perror.dat","r");
if (!fp) perror("Unable to open file for reading");
dosexterr(&info);
printf("Extended DOS error information:\n");
printf(" Extended error: %d\n",info.exterror);
printf(" Class: %x\n",info.class);
printf(" Action: %x\n",info.action);
printf(" Error Locus: %x\n",info.locus);
return 0;
}
函数名: dostounix
功 能: 转换日期和时间为UNIX时间格式
用 法: long dostounix(struct date *dateptr, struct time *timeptr);
程序例:
#include
#include
#include
#include
int main(void)
{
time_t t;
struct time d_time;
struct date d_date;
struct tm *local;
getdate(&d_date);
gettime(&d_time);
t = dostounix(&d_date, &d_time);
local = localtime(&t);
printf("Time and Date: %s\n", \
asctime(local));
return 0;
}
函数名: drawpoly
功 能: 画多边形
用 法: void far drawpoly(int numpoints, int far *polypoints);
程序例:
#include
#include
#include
#include
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int maxx, maxy;
/* our polygon array */
int poly[10];
/* 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();
/* terminate with an error code */
exit(1);
}
maxx = getmaxx();
maxy = getmaxy();
poly[0] = 20; /* 1st vertext */
poly[1] = maxy / 2;
poly[2] = maxx - 20; /* 2nd */
poly[3] = 20;
poly[4] = maxx - 50; /* 3rd */
poly[5] = maxy - 20;
poly[6] = maxx / 2; /* 4th */
poly[7] = maxy / 2;
/* drawpoly doesn';t automatically close the polygon, so we close it. */
poly[8] = poly[0];
poly[9] = poly[1];
/* draw the polygon */
drawpoly(5, poly);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: dup
功 能: 复制一个文件句柄
用 法: int dup(int handle);
程序例:
#include
#include
#include
#include
void flush(FILE *stream);
int main(void)
{
FILE *fp;
char msg[] = "This is a test";
/* create a file */
fp = fopen("DUMMY.FIL", "w");
/* write some data to the file */
fwrite(msg, strlen(msg), 1, fp);
clrscr();
printf("Press any key to flush \
DUMMY.FIL:");
getch();
/* flush the data to DUMMY.FIL without closing it */
flush(fp);
printf("\nFile was flushed, Press any \
key to quit:");
getch();
return 0;
}
void flush(FILE *stream)
{
int duphandle;
/* flush TC';s internal buffer */
fflush(stream);
/* make a duplicate file handle */
duphandle = dup(fileno(stream));
/* close the duplicate handle to flush the
DOS buffer */
close(duphandle);
}
函数名: dup2
功 能: 复制文件句柄
用 法: int dup2(int oldhandle, int newhandle);
程序例:
#include
#include
#include
#include
int main(void)
{
#define STDOUT 1
int nul, oldstdout;
char msg[] = "This is a test";
/* create a file */
nul = open("DUMMY.FIL", O_CREAT | O_RDWR,
S_IREAD | S_IWRITE);
/* create a duplicate handle for standard output */
oldstdout = dup(STDOUT);
/* redirect standard output to DUMMY.FIL by duplicating the file handle onto the file handle for standard output. */
dup2(nul, STDOUT);
/* close the handle for DUMMY.FIL */
close(nul);
/* will be redirected into DUMMY.FIL */
write(STDOUT, msg, strlen(msg));
/* restore original standard output
handle */
dup2(oldstdout, STDOUT);
/* close duplicate handle for STDOUT */
close(oldstdout);
return 0;
}
作者: starlight 时间: 2005-5-9 01:40 标题: 常用C语言库函数
函数名: ecvt
功 能: 把一个浮点数转换为字符串
用 法: char ecvt(double value, int ndigit, int *decpt, int *sign);
程序例:
#include
#include
#include
int main(void)
{
char *string;
double value;
nt dec, sign;
int ndig = 10;
clrscr();
value = 9.876;
string = ecvt(value, ndig, &dec, &sign);
printf("string = %s dec = %d \ sign = %d\n", string, dec, sign);
value = -123.45;
ndig= 15;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d sign = %d\n", string, dec, sign);
value = 0.6789e5;
/* scientific notation */
ndig = 5;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d\ sign = %d\n", string, dec, sign);
return 0;
}
函数名: ellipse
功 能: 画一椭圆
用 法: void far ellipse(int x, int y, int stangle, int endangle, int xradius, int yradius); 程序例:
#include
#include
#include
#include
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy;
int stangle = 0, endangle = 360;
int xradius = 100, yradius = 50;
/* initialize graphics, 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 ellipse */
ellipse(midx, midy, stangle, endangle, xradius, yradius);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: enable
功 能: 开放硬件中断
用 法: void enable(void);
程序例:
/* ** NOTE: This is an interrupt service routine. You can NOT compile this program with Test Stack Overflow turned on and get an executable file which will operate correctly. */
#include
#include
#include
/* The clock tick interrupt */
#define INTR 0X1C
void interrupt ( *oldhandler)(void);
int count=0;
void interrupt handler(void)
{
/*disable interrupts during the handling of the interrupt */
disable();
/* increase the global counter */
count++;
/* re enable interrupts at the end of the handler */
enable();
/* call the old routine */
oldhandler();
}
int main(void)
{
/* save the old interrupt vector */
oldhandler = getvect(INTR);
/* install the new interrupt handler */
setvect(INTR, handler);
/* loop until the counter exceeds 20 */
while (count < 20)
printf("count is %d\n",count);
/* reset the old interrupt handler */
setvect(INTR, oldhandler);
return 0;
}
函数名: eof
功 能: 检测文件结束
用 法: int eof(int *handle);
程序例:
#include
#include
#include
#include
#include
int main(void)
{
int handle;
char msg[] = "This is a test";
char ch;
/* create a file */
handle = open("DUMMY.FIL", O_CREAT | O_RDWR, S_IREAD | S_IWRITE);
/* write some data to the file */
write(handle, msg, strlen(msg));
/* seek to the beginning of the file */
lseek(handle, 0L, SEEK_SET);
/* reads chars from the file until hit EOF */
do { read(handle, &ch, 1); printf("%c", ch); }
while (!eof(handle));
close(handle);
return 0;
}
函数名: exec...
功 能: 装入并运行其它程序的函数
用 法:
int execl(char *pathname, char *arg0, arg1, ..., argn, NULL);
int execle(char *pathname, char *arg0, arg1, ..., argn, NULL, char *envp[]); int execlp(char *pathname, char *arg0, arg1, .., NULL);
int execple(char *pathname, char *arg0, arg1, ..., NULL, char *envp[]);
int execv(char *pathname, char *argv[]);
int execve(char *pathname, char *argv[], char *envp[]);
int execvp(char *pathname, char *argv[]);
int execvpe(char *pathname, char *argv[], char *envp[]);
程序例: /* execv example */
#include
#include
#include
void main(int argc, char *argv[])
{
nt i;
printf("Command line arguments:\n");
for (i=0; i);
printf("About to exec child with arg1 arg2 ...\n");
execv("CHILD.EXE", argv);
perror("exec error");
exit(1);
}
函数名: exit 功 能: 终止程序
用 法: void exit(int status);
程序例:
#include
#include
#include
int main(void)
{
int status;
printf("Enter either 1 or 2\n");
status = getch();
/* Sets DOS errorlevel */
exit(status - ';0';);
/* Note: this line is never reached */
return 0;
}
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
程序例:
#include
#include
int main(void)
{
double result;
double x = 4.0;
result = exp(x);
printf("';e'; raised to the power \ of %lf (e ^ %lf) = %lf\n", x, x, result);
return 0;
}
作者: starlight 时间: 2005-5-9 01:43 标题: 常用C语言库函数
函数名: fabs
功 能: 返回浮点数的绝对值
用 法: double fabs(double x);
程序例:
#include
#include
int main(void)
{
float number = -1234.0;
printf("number: %f absolute value: %f\n",
number, fabs(number));
return 0;
}
函数名: farcalloc
功 能: 从远堆栈中申请空间
用 法: void far *farcalloc(unsigned long units, unsigned ling unitsz);
程序例:
#include
#include
#include
#include
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
/* Note: movedata is used because you might be in a small data model, in
which case a normal string copy routine can not be used since it assumes the pointer size is near. */
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farcoreleft
功 能: 返回远堆中未作用存储区大小
用 法: long farcoreleft(void);
程序例:
#include
#include
int main(void)
{
printf("The difference between the highest allocated block in the far\n");
printf("heap and the top of the far heap is: %lu bytes\n", farcoreleft());
return 0;
}
函数名: farfree
功 能: 从远堆中释放一块
用 法: void farfree(void);
程序例:
#include
#include
#include
#include
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
/* Note: movedata is used because you might be in a small data model, in which case a normal string copy routine can';t be used since it assumes the pointer size is near. */
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farmalloc
功 能: 从远堆中分配存储块
用 法: void far *farmalloc(unsigned long size);
程序例:
#include
#include
#include
#include
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farmalloc(10);
/* copy "Hello" into allocated memory */
/* Note: movedata is used because we might be in a small data model, in which case a normal string copy routine can not be used since it assumes the pointer size is near. */
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farrealloc
功 能: 调整远堆中的分配块
用 法: void far *farrealloc(void far *block, unsigned long newsize);
程序例:
#include
#include
int main(void)
{
char far *fptr;
fptr = farmalloc(10);
printf("First address: %Fp\n", fptr);
fptr = farrealloc(fptr,20);
printf("New address : %Fp\n", fptr);
farfree(fptr);
return 0;
}
函数名: fclose
功 能: 关闭一个流
用 法: int fclose(FILE *stream);
程序例:
#include
#include
int main(void)
{
FILE *fp;
char buf[11] = "0123456789";
/* create a file containing 10 bytes */
fp = fopen("DUMMY.FIL", "w");
fwrite(&buf, strlen(buf), 1, fp);
/* close the file */
fclose(fp);
return 0;
}
函数名: fcloseall
功 能: 关闭打开流
用 法: int fcloseall(void);
程序例:
#include
int main(void)
{
int streams_closed;
/* open two streams */
fopen("DUMMY.ONE", "w");
fopen("DUMMY.TWO", "w");
/* close the open streams */
streams_closed = fcloseall();
if (streams_closed == EOF)
/* issue an error message */
perror("Error");
else
/* print result of fcloseall() function */
printf("%d streams were closed.\n", streams_closed);
return 0;
}
函数名: fcvt
功 能: 把一个浮点数转换为字符串
用 法: char *fcvt(double value, int ndigit, int *decpt, int *sign);
程序例:
#include
#include
#include
int main(void)
{
char *string;
double value;
int dec, sign;
int ndig = 10;
clrscr();
value = 9.876;
string = ecvt(value, ndig, &dec, &sign);
printf("string = %s dec = %d \
sign = %d\n", string, dec, sign);
value = -123.45;
ndig= 15;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d sign = %d\n",
string, dec, sign);
value = 0.6789e5; /* scientific
notation */
ndig = 5;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d\
sign = %d\n", string, dec, sign);
return 0;
}
函数名: fdopen
功 能: 把流与一个文件句柄相接
用 法: FILE *fdopen(int handle, char *type);
程序例:
#include
#include
#include
#include
int main(void)
{
int handle;
FILE *stream;
/* open a file */
handle = open("DUMMY.FIL", O_CREAT,
S_IREAD | S_IWRITE);
/* now turn the handle into a stream */
stream = fdopen(handle, "w");
if (stream == NULL)
printf("fdopen failed\n");
else
{
fprintf(stream, "Hello world\n");
fclose(stream);
}
return 0;
}
函数名: feof
功 能: 检测流上的文件结束符
用 法: int feof(FILE *stream);
程序例:
#include
int main(void)
{
FILE *stream;
/* open a file for reading */
stream = fopen("DUMMY.FIL", "r");
/* read a character from the file */
fgetc(stream);
/* check for EOF */
if (feof(stream))
printf("We have reached end-of-file\n");
/* close the file */
fclose(stream);
return 0;
}
函数名: ferror
功 能: 检测流上的错误
用 法: int ferror(FILE *stream);
程序例:
#include
int main(void)
{
FILE *stream;
/* open a file for writing */
stream = fopen("DUMMY.FIL", "w");
/* force an error condition by attempting to read */
(void) getc(stream);
if (ferror(stream)) /* test for an error on the stream */
{
/* display an error message */
printf("Error reading from DUMMY.FIL\n");
/* reset the error and EOF indicators */
clearerr(stream);
}
fclose(stream);
return 0;
}
函数名: fflush
功 能: 清除一个流
用 法: int fflush(FILE *stream);
程序例:
#include
#include
#include
#include
void flush(FILE *stream);
int main(void)
{
FILE *stream;
char msg[] = "This is a test";
/* create a file */
stream = fopen("DUMMY.FIL", "w");
/* write some data to the file */
fwrite(msg, strlen(msg), 1, stream);
clrscr();
printf("Press any key to flush\
DUMMY.FIL:");
getch();
/* flush the data to DUMMY.FIL without\
closing it */
flush(stream);
printf("\nFile was flushed, Press any key\
to quit:");
getch();
return 0;
}
void flush(FILE *stream)
{
int duphandle;
/* flush the stream';s internal buffer */
fflush(stream);
/* make a duplicate file handle */
duphandle = dup(fileno(stream));
/* close the duplicate handle to flush\
the DOS buffer */
close(duphandle);
}
函数名: fgetc
功 能: 从流中读取字符
用 法: int fgetc(FILE *stream);
程序例:
#include
#include
#include
int main(void)
{
FILE *stream;
char string[] = "This is a test";
char ch;
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* seek to the beginning of the file */
fseek(stream, 0, SEEK_SET);
do
{
/* read a char from the file */
ch = fgetc(stream);
/* display the character */
putch(ch);
} while (ch != EOF);
fclose(stream);
return 0;
}
函数名: fgetchar
功 能: 从流中读取字符
用 法: int fgetchar(void);
程序例:
#include
int main(void)
{
char ch;
/* prompt the user for input */
printf("Enter a character followed by : ");
/* read the character from stdin */
ch = fgetchar();
/* display what was read */
printf("The character read is: ';%c';\n", ch);
return 0;
}
函数名: fgetpos
功 能: 取得当前文件的句柄
用 法: int fgetpos(FILE *stream);
程序例:
#include
#include
int main(void)
{
FILE *stream;
char string[] = "This is a test";
fpos_t filepos;
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* report the file pointer position */
fgetpos(stream, &filepos);
printf("The file pointer is at byte %ld\n", filepos);
fclose(stream);
return 0;
}
函数名: fgets
功 能: 从流中读取一字符串
用 法: char *fgets(char *string, int n, FILE *stream);
程序例:
#include
#include
int main(void)
{
FILE *stream;
char string[] = "This is a test";
char msg[20];
/* open a file for update */
stream = fopen("DUMMY.FIL", "w+");
/* write a string into the file */
fwrite(string, strlen(string), 1, stream);
/* seek to the start of the file */
fseek(stream, 0, SEEK_SET);
/* read a string from the file */
fgets(msg, strlen(string)+1, stream);
/* display the string */
printf("%s", msg);
fclose(stream);
return 0;
}
函数名: filelength
功 能: 取文件长度字节数
用 法: long filelength(int handle);
程序例:
#include
#include
#include
#include
int main(void)
{
int handle;
char buf[11] = "0123456789";
/* create a file containing 10 bytes */
handle = open("DUMMY.FIL", O_CREAT);
write(handle, buf, strlen(buf));
/* display the size of the file */
printf("file length in bytes: %ld\n",
filelength(handle));
/* close the file */
close(handle);
return 0;
}
函数名: fillellipse
功 能: 画出并填充一椭圆
用 法: void far fillellipse(int x, int y, int xradius, int yradius);
程序例:
#include
#include
int main(void)
{
int gdriver = DETECT, gmode;
int xcenter, ycenter, i;
initgraph(&gdriver,&gmode,"");
xcenter = getmaxx() / 2;
ycenter = getmaxy() / 2;
for (i=0; i<13; i++)
{
setfillstyle(i,WHITE);
fillellipse(xcenter,ycenter,100,50);
getch();
}
closegraph();
return 0;
}
函数名: fillpoly
功 能: 画并填充一个多边形
用 法: void far fillpoly(int numpoints, int far *polypoints);
程序例:
#include