怎么求c语言函数 用c语言求函数

求C语言函数大全

函数名: abort

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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; i80; 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);

}

求C语言的基本函数？

函数名:

difftime

功

能:

计算两个时刻之间的时间差

用

法:

double

difftime(time_t

time2,

time_t

time1);

程序例:

#include

#include

#include

#include

int

main(void)

{

time_t

first,

second;

clrscr();

first

=

time(NULL);

/*

Gets

system

time

*/

delay(2000);

/*

Waits

2

secs

*/

second

=

time(NULL);

/*

Gets

system

time

again

*/

printf("The

difference

is:

%f

\

seconds\n",difftime(second,first));

getch();

return

0;

}

函数名:

disable

功

能:

屏蔽中断

用

法:

void

disable(void);

程序例:

/***NOTE:

This

is

an

interrupt

service

routine.

You

cannot

compile

this

program

with

Test

Stack

Overflow

turned

on

and

get

an

executable

file

that

operates

correctly.

*/

#include

#include

#include

#define

INTR

0X1C

/*

The

clock

tick

interrupt

*/

void

interrupt

(

*oldhandler)(void);

int

count=0;

void

interrupt

handler(void)

{

/*

disable

interrupts

during

the

handling

of

the

interrupt

*/

disable();

/*

increase

the

global

counter

*/

count++;

/*

reenable

interrupts

at

the

end

of

the

handler

*/

enable();

/*

call

the

old

routine

*/

oldhandler();

}

int

main(void)

{

/*

save

the

old

interrupt

vector

*/

oldhandler

=

getvect(INTR);

/*

install

the

new

interrupt

handler

*/

setvect(INTR,

handler);

/*

loop

until

the

counter

exceeds

20

*/

while

(count

20)

printf("count

is

%d\n",count);

/*

reset

the

old

interrupt

handler

*/

setvect(INTR,

oldhandler);

return

0;

}

c语言求函数值

int fun(int x )

{

if(x0  x!=3)

return x*x+x+6;

if((x=0  x10)  (x!=2)  (x!=3))

return  x*x - 5*x+6;

return x*x-x-1;

}

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C语言问题之求函数

#include stdio.h

int main()

{

int repeat,i,m,n,sum;

for(scanf("%d",repeat);repeat0;repeat--)

{

for(scanf("%d%d",m,n);mn;m++)

{

for(sum=0,i=1;im;++i)

{

if(m%i==0)

{

sum+=i;

}

}

if(sum==m)

{

printf("%d ",m);

}

}

printf("\n");

}

return 0;

}