C语言函数 - A开头

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);

}