功能名称: abort
动力 能够: 异常终止的过程的
使用 法国: void abort(void);
程序示例:
#include <stdio.h> #include <stdlib.h> int main(void) { printf("Calling abort() "); 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 <stdio.h> #include <math.h> int main(void) { int number = -1234; printf("number: %d absolute value: %d ", 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 <stdio.h> #include <conio.h> #include <process.h> #include <dos.h> int main(void) { int i, strt, ch_out, sector; char buf[512]; printf("Insert a diskette into drive A and press any key "); getch(); sector = 0; if (absread(0, 1, sector, &buf) != 0) { perror("Disk problem"); exit(1); } printf("Read OK "); strt = 3; for (i=0; i<80; i++) { ch_out = buf[strt+i]; putchar(ch_out); } printf(" "); return(0); }
函数名: access
功 能: 确定文件的訪问权限
用 法: int access(const char *filename, int amode);
程序例:
#include <stdio.h> #include <io.h> int file_exists(char *filename); int main(void) { printf("Does NOTEXIST.FIL exist: %s ", 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 <stdio.h> #include <math.h> int main(void) { double result; double x = 0.5; result = acos(x); printf("The arc cosine of %lf is %lf ", 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 <dos.h> #include <alloc.h> #include <stdio.h> 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 ", segp); else printf("Failed: maximum number of paragraphs available is %u ", 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 <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 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 ", 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 <stdio.h> #include <string.h> #include <time.h> 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 ", str); return 0; }
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> int main(void) { double result; double x = 0.5; result = asin(x); printf("The arc sin of %lf is %lf ", x, result); return(0); }
函数名: assert
功 能: 測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> 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 <stdio.h> #include <math.h> int main(void) { double result; double x = 0.5; result = atan(x); printf("The arc tangent of %lf is %lf ", 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 <stdio.h> #include <math.h> 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 ", (y / x), result); return 0; }
函数名: atexit
功 能: 注冊终止函数
用 法: int atexit(atexit_t func);
程序例:
#include <stdio.h> #include <stdlib.h> void exit_fn1(void) { printf("Exit function #1 called "); } void exit_fn2(void) { printf("Exit function #2 called "); } 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 <stdlib.h> #include <stdio.h> int main(void) { float f; char *str = "12345.67"; f = atof(str); printf("string = %s float = %f ", 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 <stdlib.h> #include <stdio.h> int main(void) { int n; char *str = "12345.67"; n = atoi(str); printf("string = %s integer = %d ", 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 <stdlib.h> #include <stdio.h> int main(void) { long l; char *str = "98765432"; l = atol(lstr); printf("string = %s integer = %ld ", str, l); return(0); }
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