C语言的函数!

内财数模协会 · 发表于 2004-5-8 17:19:43

<

>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 <stdio.h>
#include <math.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:20:05

<

>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 <stdio.h>
#include <alloc.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:20:20

<

>函数名: ceil
功能: 向上舍入
用法: double ceil(double x);
程序例: <

>#include <math.h>
#include <stdio.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:20:32

<

>函数名: cgets
功能: 从控制台读字符串
用法: char *cgets(char *str);
程序例: <

>#include <stdio.h>
#include <conio.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:20:42

<

>函数名: chdir
功能: 改变工作目录
用法: int chdir(const char *path);
程序例: <

>#include <stdio.h>
#include <stdlib.h>
#include <dir.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:20:52

<

>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 <sys\stat.h>
#include <stdio.h>
#include <io.h> <

>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);
}

内财数模协会 · 发表于 2004-5-8 17:21:02

<

>函数名: chsize
功能: 改变文件大小
用法: int chsize(int handle, long size);
程序例: <

>#include <string.h>
#include <fcntl.h>
#include <io.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:21:13

<

>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 <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:21:23

<

>函数名: cleardevice
功能: 清除图形屏幕
用法: void far cleardevice(void);
程序例: <

>#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h> <

>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;
}

内财数模协会 · 发表于 2004-5-8 17:21:33

<

>函数名: clearerr
功能: 复位错误标志
用法:void clearerr(FILE *stream);
程序例: <

>#include <stdio.h> <

>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;
}

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