C语言高级函数实例.doc

下面为C标准库中的一些函数：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 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: 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: 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(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: %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, 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: %sn, 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 str80; /* 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 Dayligh