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<title>网上学堂 --> C语言编程宝典之一 -->函数名: c</title>
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<td bgcolor="#FFE6B0" bordercolor="#8080FF" class="p9"><font
color="#BB0000">导航条：--></font> <a
href="../../index.html">网上学堂</a> --> <a
href="../tcindex.htm"><font face="宋体">C</font>语言编程宝典之一</a>
-->函数名: c</td>
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<td bordercolor="#8080FF" class="p9">函数名: cabs <br>
功 能: 计算复数的绝对值 <br>
用 法: double cabs(struct complex z); <br>
程序例: <p>#include <stdio.h> <br>
#include <math.h> </p>
<p>int main(void) <br>
{ <br>
struct complex z; <br>
double val; </p>
<p> z.x = 2.0; <br>
z.y = 1.0; <br>
val = cabs(z); </p>
<p> printf("The absolute value of %.2lfi
%.2lfj is %.2lf", z.x, z.y, val); <br>
return 0; <br>
} <br>
<br>
<br>
</p>
<p>函数名: calloc <br>
功 能: 分配主存储器 <br>
用 法: void *calloc(size_t nelem, size_t elsize);
<br>
程序例: </p>
<p>#include <stdio.h> <br>
#include <alloc.h> </p>
<p>int main(void) <br>
{ <br>
char *str = NULL; </p>
<p> /* allocate memory for string */ <br>
str = calloc(10, sizeof(char)); </p>
<p> /* copy "Hello" into string */ <br>
strcpy(str, "Hello"); </p>
<p> /* display string */ <br>
printf("String is %s\n", str); </p>
<p> /* free memory */ <br>
free(str); </p>
<p> return 0; <br>
} <br>
<br>
<br>
</p>
<p>函数名: ceil <br>
功 能: 向上舍入 <br>
用 法: double ceil(double x); <br>
程序例: </p>
<p>#include <math.h> <br>
#include <stdio.h> </p>
<p>int main(void) <br>
{ <br>
double number = 123.54; <br>
double down, up; </p>
<p> down = floor(number); <br>
up = ceil(number); </p>
<p> printf("original number
%5.2lf\n", number); <br>
printf("number rounded down
%5.2lf\n", down); <br>
printf("number rounded up
%5.2lf\n", up); </p>
<p> return 0; <br>
} <br>
<br>
<br>
</p>
<p>函数名: cgets <br>
功 能: 从控制台读字符串 <br>
用 法: char *cgets(char *str); <br>
程序例: </p>
<p>#include <stdio.h> <br>
#include <conio.h> </p>
<p>int main(void) <br>
{ <br>
char buffer[83]; <br>
char *p; </p>
<p> /* There's space for 80 characters plus
the NULL terminator */ <br>
buffer[0] = 81; </p>
<p> printf("Input some chars:"); <br>
p = cgets(buffer); <br>
printf("\ncgets read %d characters:
\"%s\"\n", buffer[1], p); <br>
printf("The returned pointer is %p,
buffer[0] is at %p\n", p, &buffer); </p>
<p> /* Leave room for 5 characters plus the
NULL terminator */ <br>
buffer[0] = 6; </p>
<p> printf("Input some chars:"); <br>
p = cgets(buffer); <br>
printf("\ncgets read %d characters:
\"%s\"\n", buffer[1], p); <br>
printf("The returned pointer is %p,
buffer[0] is at %p\n", p, &buffer); <br>
return 0; <br>
} <br>
<br>
<br>
</p>
<p>函数名: chdir <br>
功 能: 改变工作目录 <br>
用 法: int chdir(const char *path); <br>
程序例: </p>
<p>#include <stdio.h> <br>
#include <stdlib.h> <br>
#include <dir.h> </p>
<p>char old_dir[MAXDIR]; <br>
char new_dir[MAXDIR]; </p>
<p>int main(void) <br>
{ <br>
if (getcurdir(0, old_dir)) <br>
{ <br>
perror("getcurdir()"); <br>
exit(1); <br>
} <br>
printf("Current directory is:
\\%s\n", old_dir); </p>
<p> if (chdir("\\")) <br>
{ <br>
perror("chdir()"); <br>
exit(1); <br>
} </p>
<p> if (getcurdir(0, new_dir)) <br>
{ <br>
perror("getcurdir()"); <br>
exit(1); <br>
} <br>
printf("Current directory is now:
\\%s\n", new_dir); </p>
<p> printf("\nChanging back to orignal
directory: \\%s\n", old_dir); <br>
if (chdir(old_dir)) <br>
{ <br>
perror("chdir()"); <br>
exit(1); <br>
} </p>
<p> return 0; <br>
} <br>
<br>
</p>
<p>函数名: _chmod, chmod <br>
功 能: 改变文件的访问方式 <br>
用 法: int chmod(const char *filename, int
permiss); <br>
程序例: </p>
<p>#include <sys\stat.h> <br>
#include <stdio.h> <br>
#include <io.h> </p>
<p>void make_read_only(char *filename); </p>
<p>int main(void) <br>
{ <br>
make_read_only("NOTEXIST.FIL"); <br>
make_read_only("MYFILE.FIL"); <br>
return 0; <br>
} </p>
<p>void make_read_only(char *filename) <br>
{ <br>
int stat; </p>
<p> stat = chmod(filename, S_IREAD); <br>
if (stat) <br>
printf("Couldn't make
%s read-only\n", filename); <br>
else <br>
printf("Made %s
read-only\n", filename); <br>
} <br>
<br>
<br>
</p>
<p>函数名: chsize <br>
功 能: 改变文件大小 <br>
用 法: int chsize(int handle, long size); <br>
程序例: </p>
<p>#include <string.h> <br>
#include <fcntl.h> <br>
#include <io.h> </p>
<p>int main(void) <br>
{ <br>
int handle; <br>
char buf[11] = "0123456789"; </p>
<p> /* create text file containing 10 bytes
*/ <br>
handle = open("DUMMY.FIL",
O_CREAT); <br>
write(handle, buf, strlen(buf)); </p>
<p> /* truncate the file to 5 bytes in size
*/ <br>
chsize(handle, 5); </p>
<p> /* close the file */ <br>
close(handle); <br>
return 0; <br>
} <br>
<br>
</p>
<p>函数名: circle <br>
功 能: 在给定半径以(x, y)为圆心画圆 <br>
用 法: void far circle(int x, int y, int radius);
<br>
程序例: </p>
<p>#include <graphics.h> <br>
#include <stdlib.h> <br>
#include <stdio.h> <br>
#include <conio.h> </p>
<p>int main(void) <br>
{ <br>
/* request auto detection */ <br>
int gdriver = DETECT, gmode, errorcode; <br>
int midx, midy; <br>
int radius = 100; </p>
<p> /* initialize graphics and local
variables */ <br>
initgraph(&gdriver, &gmode,
""); </p>
<p> /* read result of initialization */ <br>
errorcode = graphresult(); <br>
if (errorcode != grOk) /* an error
occurred */ <br>
{ <br>
printf("Graphics
error: %s\n", grapherrormsg(errorcode)); <br>
printf("Press any key
to halt:"); <br>
getch(); <br>
exit(1); /* terminate with
an error code */ <br>
} </p>
<p> midx = getmaxx() / 2; <br>
midy = getmaxy() / 2; <br>
setcolor(getmaxcolor()); </p>
<p> /* draw the circle */ <br>
circle(midx, midy, radius); </p>
<p> /* clean up */ <br>
getch(); <br>
closegraph(); <br>
return 0; <br>
} <br>
<br>
<br>
</p>
<p>函数名: cleardevice <br>
功 能: 清除图形屏幕 <br>
用 法: void far cleardevice(void); <br>
程序例: </p>
<p>#include <graphics.h> <br>
#include <stdlib.h> <br>
#include <stdio.h> <br>
#include <conio.h> </p>
<p>int main(void) <br>
{ <br>
/* request auto detection */ <br>
int gdriver = DETECT, gmode, errorcode; <br>
int midx, midy; </p>
<p> /* initialize graphics and local
variables */ <br>
initgraph(&gdriver, &gmode,
""); </p>
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