a.txt

C语言函数大全

函数名: abort 
功 能: 异常终止一个进程 
用 法: void abort(void); 
程序例: 
#include <stdio.h> 
#include <stdlib.h> 
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 <stdio.h> 
#include <math.h> 

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 <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\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 <stdio.h> 
#include <io.h> 

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 <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\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 <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\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 <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\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 <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\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 <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\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 <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\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 <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\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 <stdio.h> 
#include <stdlib.h> 

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 <stdlib.h> 
#include <stdio.h> 

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 <stdlib.h> 
#include <stdio.h> 

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 <stdlib.h> 
#include <stdio.h> 

int main(void) 
{ 
long l; 
char *str = "98765432"; 

l = atol(lstr); 
printf("string = %s integer = %ld\n", str, l); 
return(0); 
}