C语言函数集（一）

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(inti);

程序例:

include
<stdio.h>

#include
<math.h>

int main(void){

 intnumber
= -1234;

 printf("number: %d absolute value: %d\n",number,
abs(number));

 return0;

}

 

函数名:absread,
abswirte

功 能:绝对磁盘扇区读、写数据

用法:int
absread(intdrive,
int nsects,
int sectno,
void *buffer);

int abswrite(intdrive,
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){

 inti,
strt, ch_out,
sector;

 charbuf[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");

 return0;

}

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(doublex);

程序例:

#include
<stdio.h>

#include
<math.h>

int main(void){

 doubleresult;

 doublex
= 0.5;

 result
= acos(x);

 printf("The arc cosine of %lf is %lf\n",x,
result);

 return0;

}

 

 

 

 

函数名:allocmem

功 能:分配DOS存储段

用 法:int
allocmem(unsignedsize,
unsigned*seg);

程序例:

#include
<dos.h>

#include
<alloc.h>

#include
<stdio.h>

int main(void){

 unsigned intsize,
segp;

 intstat;

 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);

 return0;

}

 

 

 

 

函数名:arc

功 能:画一弧线

用 法:void
far arc(intx,
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 */

 intgdriver
= DETECT,gmode,
errorcode;

 intmidx,
midy;

 intstangle
= 45,endangle
= 135;

 intradius
= 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();

 return0;

}

 

 

 

 

函数名:asctime

功 能:转换日期和时间为ASCII码

用 法:char
*asctime(const structtm
*tblock);

程序例:

#include
<stdio.h>

#include
<string.h>

#include
<time.h>

int main(void){

 structtm t;

 charstr[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);

 return0;

}

 

 

 

 

函数名:asin

功 能:反正弦函数

用 法:double
asin(doublex);

程序例:

#include
<stdio.h>

#include
<math.h>

int main(void){

 doubleresult;

 doublex
= 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(inttest);

程序例:#include<assert.h>

#include
<stdio.h>

#include
<stdlib.h>

struct ITEM{

 intkey;

 intvalue;

};/* add item to list, make sure list is not null */

void additem(structITEM
*itemptr) {

 assert(itemptr!=
NULL);

 /* add item to list */

}

int main(void){

 additem(NULL);

 return0;

}

 

 

 

 

 

函数名:atan

功 能:反正切函数

用 法:double
atan(doublex);

程序例:

#include
<stdio.h>

#include
<math.h>

int main(void){

double result;

 doublex
= 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(doubley,
double x);

程序例:

#include
<stdio.h>

#include
<math.h>

int main(void){

 doubleresult;

 doublex
= 90.0,y
= 45.0;

 result
= atan2(y,
x);

 printf("The arc tangent ratio of %lf is %lf\n", (y/
x), result);

 return0;

}

 

 

 

 

 

 

 

 

 

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);

 return0;

}

 

 

 

 

 

 

 

 

 

 

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){

 floatf;

 char*str
= "12345.67";

 f
= atof(str);

 printf("string = %s float = %f\n",str,
f);

 return0;

}

 

 

 

 

 

 

 

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){

 intn;

 char*str
= "12345.67";

 n
= atoi(str);

 printf("string = %s integer = %d\n",str,
n);

 return0;

}

 

 

 

 

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){

 longl;

 char*str
= "98765432";

 l
= atol(lstr);

 printf("string = %s integer = %ld\n",str,
l);

 return(0);

}