C预言库函数示例A.docx

1、C预言库函数示例A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 valu

2、e: %dn, 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,

3、ch_out, sector; char buf512; printf(Insert a diskette into drive A and press any keyn); getch(); sector = 0; if (absread(0, 1, sector, &buf) != 0) perror(Disk problem); exit(1); printf(Read OKn); strt = 3; for (i=0; i80; i+) ch_out = bufstrt+i; putchar(ch_out); printf(n); return(0); 函数名: access 功 能:

4、 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: %sn, file_exists(NOTEXISTS.FIL) ? YES : NO); return 0; int file_exists(char *filename) return (access(filename, 0) = 0); 函数名: acos 功 能:

5、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 %lfn, 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(v

6、oid) 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: %xn, segp); else printf(Failed: maximum number of paragraphs available is %un, stat); return 0; 函数名: arc 功 能: 画一弧线 用 法: void far arc(int x,

7、 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(&gd

8、river, &gmode, ); /* read result of initialization */ errorcode = graphresult(); /* an error occurred */ if (errorcode != grOk) printf(Graphics error: %sn, grapherrormsg(errorcode); printf(Press any key to halt:); getch(); exit(1); /* terminate with an error code */ midx = getmaxx() / 2; midy = getm

9、axy() / 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 str80; /* sampl

10、e 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

11、 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(%sn, 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 =

12、0.5; result = asin(x); printf(The arc sin of %lf is %lfn, 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(

13、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 %lfn, x, result); return(0); 函数名: atan2 功 能: 计算Y/X

14、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 %lfn, (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 v

15、oid exit_fn1(void) printf(Exit function #1 calledn); void exit_fn2(void) printf(Exit function #2 calledn); 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

16、#include int main(void) float f; char *str = 12345.67; f = atof(str); printf(string = %s float = %fn, 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 = %dn, 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 = %ldn, str, l); return(0);