函數名: cabs
功 能: 計算復數的絕對值
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;
}
函數名: calloc
功 能: 分配主存儲器
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
", str);
/* free memory */
free(str);
return 0;
}
函數名: ceil
功 能: 向上捨入
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
", number);
printf("number rounded down %5.2lf
", down);
printf("number rounded up %5.2lf
", up);
return 0;
}
函數名: cgets
功 能: 從控制台讀字符串
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("
cgets read %d characters: "%s"
", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p
", p, &buffer);
/* Leave room for 5 characters plus the NULL terminator */
buffer[0] = 6;
printf("Input some chars:");
p = cgets(buffer);
printf("
cgets read %d characters: "%s"
", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p
", p, &buffer);
return 0;
}
函數名: chdir
功 能: 改變工作目錄
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
", old_dir);
if (chdir("\"))
{
perror("chdir()");
exit(1);
}
if (getcurdir(0, new_dir))
{
perror("getcurdir()");
exit(1);
}
printf("Current directory is now: \%s
", new_dir);
printf("
Changing back to orignal directory: \%s
", old_dir);
if (chdir(old_dir))
{
perror("chdir()");
exit(1);
}
return 0;
}
函數名: _chmod, chmod
功 能: 改變文件的訪問方式
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
", filename);
else
printf("Made %s read-only
", filename);
}
函數名: chsize
功 能: 改變文件大小
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;
}
函數名: circle
功 能: 在給定半徑以(x, y)為圓心畫圓
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
", 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;
}
函數名: cleardevice
功 能: 清除圖形屏幕
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
", 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;
}
函數名: clearerr
功 能: 復位錯誤標志
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
",ch);
if (ferror(fp))
{
/* display an error message */
printf("Error reading from DUMMY.FIL
");
/* reset the error and EOF indicators */
clearerr(fp);
}
fclose(fp);
return 0;
}
函數名: clearviewport
功 能: 清除圖形視區
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
", 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;
}
函數名: _close, close
功 能: 關閉文件句柄
用 法: int close(int handle);
程序例:
#include<
