C语言的函数!
**** Hidden Message *****[此贴子已经被作者于2004-5-10 9:01:54编辑过]
<P>函数名: abs
功能: 求整数的绝对值
用法: int abs(int i);
程序例:
#include <stdio.h>
#include <math.h> <P>int main(void)
{
int number = -1234; <P>printf("number: %dabsolute value: %d\n", number, abs(number));
return 0;
}
</P> <P>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 */ <P>#include <stdio.h>
#include <conio.h>
#include <process.h>
#include <dos.h> <P>int main(void)
{
int i, strt, ch_out, sector;
char buf; <P>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;
putchar(ch_out);
}
printf("\n");
return(0);
}
</P> <P>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 <stdio.h>
#include <io.h> <P>int file_exists(char *filename); <P>int main(void)
{
printf("Does NOTEXIST.FIL exist: %s\n",
file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
return 0;
} <P>int file_exists(char *filename)
{
return (access(filename, 0) == 0);
}
</P> <P>函数名: acos
功能: 反余弦函数
用法: double acos(double x);
程序例:
#include <stdio.h>
#include <math.h> <P>int main(void)
{
double result;
double x = 0.5; <P>result = acos(x);
printf("The arc cosine of %lf is %lf\n", x, result);
return 0;
}
</P> <P>函数名: allocmem
功能: 分配DOS存储段
用法: int allocmem(unsigned size, unsigned *seg);
程序例:
#include <dos.h>
#include <alloc.h>
#include <stdio.h> <P>int main(void)
{
unsigned int size, segp;
int stat; <P>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); <P>return 0;
}
</P> <P>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 <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h> <P>int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int midx, midy;
int stangle = 45, endangle = 135;
int radius = 100; <P> /* initialize graphics and local variables */
initgraph(&gdriver, &gmode, ""); <P> /* 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(); <P> exit(1); /* terminate with an error code */
} <P> midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor()); <P> /* draw arc */
arc(midx, midy, stangle, endangle, radius); <P> /* clean up */
getch();
closegraph();
return 0;
}
</P> <P>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 <stdio.h>
#include <string.h>
#include <time.h> <P>int main(void)
{
struct tm t;
char str; <P> /* sample loading of tm structure*/ <P> 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 */ <P> /* converts structure to null terminated
string */ <P> strcpy(str, asctime(&t));
printf("%s\n", str); <P> return 0;
}
</P> <P>函数名: asin
功能: 反正弦函数
用法: double asin(double x);
程序例:
#include <stdio.h>
#include <math.h> <P>int main(void)
{
double result;
double x = 0.5; <P> result = asin(x);
printf("The arc sin of %lf is %lf\n", x, result);
return(0);
}
</P> <P>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 <assert.h>
#include <stdio.h>
#include <stdlib.h> <P>struct ITEM {
int key;
int value;
}; <P>/* add item to list, make sure list is not null */
void additem(struct ITEM *itemptr) {
assert(itemptr != NULL);
/* add item to list */
} <P>int main(void)
{
additem(NULL);
return 0;
}
</P>