C语言函数大全（包含大部分的函数，每个函数包括函数名，功能，用法，举例。）
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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, int 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);
}
函数名: bar
功 能: 画一个二维条形图
用 法: void far bar(int left, int top, int right, int bottom);
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, i;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
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;
/* loop through the fill patterns */
for (i=SOLID_FILL; i<USER_FILL; i++)
{
/* set the fill style */
setfillstyle(i, getmaxcolor());
/* draw the bar */
bar(midx-50, midy-50, midx+50,
midy+50);
getch();
}
/* clean up */
closegraph();
return 0;
}
函数名: bar3d
功 能: 画一个三维条形图
用 法: void far bar3d(int left, int top, int right, int bottom, int depth, int t
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, i;
/* initialize graphics, local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1); /* terminate with error code */
}
midx = getmaxx() / 2;
midy = getmaxy() / 2;
/* loop through the fill patterns */
for (i=EMPTY_FILL; i<USER_FILL; i++)
{
/* set the fill style */
setfillstyle(i, getmaxcolor());
/* draw the 3-d bar */
bar3d(midx-50, midy-50, midx+50, midy+50, 10, 1);
getch();
}
/* clean up */
closegraph();
return 0;
}
函数名: bdos
功 能: DOS系统调用
用 法: int bdos(int dosfun, unsigned dosdx, unsigned dosal);
程序例:
#include <stdio.h>
#include <dos.h>
/* Get current drive as 'A', 'B', ... */
char current_drive(void)
{
char curdrive;
/* Get current disk as 0, 1, ... */
curdrive = bdos(0x19, 0, 0);
return('A' + curdrive);
}
int main(void)
{
printf("The current drive is %c:\n", current_drive());
return 0;
}
函数名: bdosptr
功 能: DOS系统调用
用 法: int bdosptr(int dosfun, void *argument, unsigned dosal);
程序例:
#include <string.h>
#include <stdio.h>
#include <dir.h>
#include <dos.h>
#include <errno.h>
#include <stdlib.h>
#define BUFLEN 80
int main(void)
{
char buffer[BUFLEN];
int test;
printf("Enter full pathname of a directory\n");
gets(buffer);
test = bdosptr(0x3B,buffer,0);
if(test)
{
printf("DOS error message: %d\n", errno);
/* See errno.h for error listings */
exit (1);
}
getcwd(buffer, BUFLEN);
printf("The current directory is: %s\n", buffer);
return 0;
}
函数名: bioscom
功 能: 串行I/O通信
用 法: int bioscom(int cmd, char abyte, int port);
程序例:
#include <bios.h>
#include <conio.h>
#define COM1
#define DATA_READY 0x100
0
#define TRUE
#define FALSE
1
0
#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)
int main(void)
{
int in, out, status, DONE = FALSE;
bioscom(0, SETTINGS, COM1);
cprintf("... BIOSCOM [ESC] to exit ...\n");
while (!DONE)
{
status = bioscom(3, 0, COM1);
if (status & DATA_READY)
if ((out = bioscom(2, 0, COM1) & 0x7F) != 0)
putch(out);
if (kbhit())
{
if ((in = getch()) == '\x1B')
DONE = TRUE;
bioscom(1, in, COM1);
}
}
return 0;
}
函数名: biosdisk
功 能: 软硬盘I/O
用 法: int biosdisk(int cmd, int drive, int head, int track, int sector
int nsects, void *buffer);
程序例:
#include <bios.h>
#include <stdio.h>
int main(void)
{
int result;
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) :
(printf("Drive A: Not Ready\n"));
return 0;
}
函数名: biosequip
功 能: 检查设备
用 法: int biosequip(void);
程序例:
#include <bios.h>
#include <stdio.h>
int main(void)
{
int result;
char buffer[512];
printf("Testing to see if drive a: is ready\n");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Ready\n")) :
(printf("Drive A: Not Ready\n"));
return 0;
}
函数名: bioskey
功 能: 直接使用BIOS服务的键盘接口
用 法: int bioskey(int cmd);
程序例:
#include <stdio.h>
#include <bios.h>
#include <ctype.h>
#define RIGHT 0x01
#define LEFT 0x02
#define CTRL 0x04
#define ALT 0x08
int main(void)
{
int key, modifiers;
/* function 1 returns 0 until a key is pressed */
while (bioskey(1) == 0);
/* function 0 returns the key that is waiting */
key = bioskey(0);
/* use function 2 to determine if shift keys were used */
modifiers = bioskey(2);
if (modifiers)
{
printf("[");
if (modifiers & RIGHT) printf("RIGHT");
if (modifiers & LEFT) printf("LEFT");
if (modifiers & CTRL) printf("CTRL");
if (modifiers & ALT) printf("ALT");
printf("]");
}
/* print out the character read */
if (isalnum(key & 0xFF))
printf("'%c'\n", key);
else
printf("%#02x\n", key);
return 0;
}
函数名: biosmemory
功 能: 返回存储块大小
用 法:int biosmemory(void);
程序例:
#include <stdio.h>
#include <bios.h>
int main(void)
{
int memory_size;
memory_size = biosmemory(); /* returns value up to 640K */
printf("RAM size = %dK\n",memory_size);
return 0;
}
函数名: biosprint
功 能: 直接使用BIOS服务的打印机I/O
用 法: int biosprint(int cmd, int byte, int port);
程序例:
#include <stdio.h>
#include <conio.h>
#include <bios.h>
int main(void)
{
#define STATUS 2 /* printer status command */
#define PORTNUM 0 /* port number for LPT1 */
int status, abyte=0;
printf("Please turn off your printer. Press any key to continue\n");
getch();
status = biosprint(STATUS, abyte, PORTNUM);
if (status & 0x01)
printf("Device time out.\n");
if (status & 0x08)
printf("I/O error.\n");
if (status & 0x10)
printf("Selected.\n");
if (status & 0x20)
printf("Out of paper.\n");
if (status & 0x40)
printf("Acknowledge.\n");
if (status & 0x80)
printf("Not busy.\n");
return 0;
}
函数名: biostime
功 能: 读取或设置BIOS时间
用 法: long biostime(int cmd, long newtime);
程序例:
#include <stdio.h>
#include <bios.h>
#include <time.h>
#include <conio.h>
int main(void)
{
long bios_time;
clrscr();
cprintf("The number of clock ticks since midnight is:\r\n");
cprintf("The number of seconds since midnight is:\r\n");
cprintf("The number of minutes since midnight is:\r\n");
cprintf("The number of hours since midnight is:\r\n");
cprintf("\r\nPress any key to quit:");
while(!kbhit())
{
bios_time = biostime(0, 0L);
gotoxy(50, 1);
cprintf("%lu", bios_time);
gotoxy(50, 2);
cprintf("%.4f", bios_time / CLK_TCK);
gotoxy(50, 3);
cprintf("%.4f", bios_time / CLK_TCK / 60);
gotoxy(50, 4);
cprintf("%.4f", bios_time / CLK_TCK / 3600);
}
return 0;
}
函数名: brk
功 能: 改变数据段空间分配
用 法: int brk(void *endds);
程序例:
#include <stdio.h>
#include <alloc.h>
int main(void)
{
char *ptr;
printf("Changing allocation with brk()\n");
ptr = malloc(1);
printf("Before brk() call: %lu bytes free\n", coreleft());
brk(ptr+1000);
printf(" After brk() call: %lu bytes free\n", coreleft());
return 0;
}
函数名: bsearch
功 能: 二分法搜索
用 法: void *bsearch(const void *key, const void *base, size_t *nelem, size_t w
程序例:
#include <stdlib.h>
#include <stdio.h>
#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
int numarray[] = {123, 145, 512, 627, 800, 933};
int numeric (const int *p1, const int *p2)
{
return(*p1 - *p2);
}
int lookup(int key)
{
int *itemptr;
/* The cast of (int(*)(const void *,const void*))
is needed to avoid a type mismatch error at
compile time */
itemptr = bsearch (&key, numarray, NELEMS(numarray),
sizeof(int), (int(*)(const void *,const void *))numeric);
return (itemptr != NULL);
}
int main(void)
{
if (lookup(512))
printf("512 is in the table.\n");
else
printf("512 isn't in the table.\n");
return 0;
}
函数名: cabs
功 能: 计算复数的绝对值
用 法: double cabs(struct complex z);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
struct complex z;
double val;
z.x = 2.0;
z.y = 1.0;
val = cabs(z);
printf("The absolute value of %.2lfi %.2lfj is %.2lf", z.x, z.y, val);
return 0;
}
函数名: calloc
功 能: 分配主存储器
用 法: void *calloc(size_t nelem, size_t elsize);
程序例:
#include <stdio.h>
#include <alloc.h>
int main(void)
{
char *str = NULL;
/* allocate memory for string */
str = calloc(10, sizeof(char));
/* copy "Hello" into string */
strcpy(str, "Hello");
/* display string */
printf("String is %s\n", str);
/* free memory */
free(str);
return 0;
}
函数名: ceil
功 能: 向上舍入
用 法: double ceil(double x);
程序例:
#include <math.h>
#include <stdio.h>
int main(void)
{
double number = 123.54;
double down, up;
down = floor(number);
up = ceil(number);
printf("original number
%5.2lf\n", number);
printf("number rounded down %5.2lf\n", down);
printf("number rounded up %5.2lf\n", up);
return 0;
}
函数名: cgets
功 能: 从控制台读字符串
用 法: char *cgets(char *str);
程序例:
#include <stdio.h>
#include <conio.h>
int main(void)
{
char buffer[83];
char *p;
/* There's space for 80 characters plus the NULL terminator */
buffer[0] = 81;
printf("Input some chars:");
p = cgets(buffer);
printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);
/* Leave room for 5 characters plus the NULL terminator */
buffer[0] = 6;
printf("Input some chars:");
p = cgets(buffer);
printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);
printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);
return 0;
}
函数名: chdir
功 能: 改变工作目录
用 法: int chdir(const char *path);
程序例:
#include <stdio.h>
#include <stdlib.h>
#include <dir.h>
char old_dir[MAXDIR];
char new_dir[MAXDIR];
int main(void)
{
if (getcurdir(0, old_dir))
{
perror("getcurdir()");
exit(1);
}
printf("Current directory is: \\%s\n", old_dir);
if (chdir("\\"))
{
perror("chdir()");
exit(1);
}
if (getcurdir(0, new_dir))
{
perror("getcurdir()");
exit(1);
}
printf("Current directory is now: \\%s\n", new_dir);
printf("\nChanging back to orignal directory: \\%s\n", old_dir);
if (chdir(old_dir))
{
perror("chdir()");
exit(1);
}
return 0;
}
函数名: _chmod, chmod
功 能: 改变文件的访问方式
用 法: int chmod(const char *filename, int permiss);
程序例:
#include <sys\stat.h>
#include <stdio.h>
#include <io.h>
void make_read_only(char *filename);
int main(void)
{
make_read_only("NOTEXIST.FIL");
make_read_only("MYFILE.FIL");
return 0;
}
void make_read_only(char *filename)
{
int stat;
stat = chmod(filename, S_IREAD);
if (stat)
printf("Couldn't make %s read-only\n", filename);
else
printf("Made %s read-only\n", filename);
}
函数名: chsize
功 能: 改变文件大小
用 法: int chsize(int handle, long size);
程序例:
#include <string.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
char buf[11] = "0123456789";
/* create text file containing 10 bytes */
handle = open("DUMMY.FIL", O_CREAT);
write(handle, buf, strlen(buf));
/* truncate the file to 5 bytes in size */
chsize(handle, 5);
/* close the file */
close(handle);
return 0;
}
函数名: circle
功 能: 在给定半径以(x, y)为圆心画圆
用 法: void far circle(int x, int y, 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 radius = 100;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
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 the circle */
circle(midx, midy, radius);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: cleardevice
功 能: 清除图形屏幕
用 法: void far cleardevice(void);
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;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
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());
/* for centering screen messages */
settextjustify(CENTER_TEXT, CENTER_TEXT);
/* output a message to the screen */
outtextxy(midx, midy, "press any key to clear the screen:");
/* wait for a key */
getch();
/* clear the screen */
cleardevice();
/* output another message */
outtextxy(midx, midy, "press any key to quit:");
/* clean up */
getch();
closegraph();
return 0;
}
函数名: clearerr
功 能: 复位错误标志
用 法:void clearerr(FILE *stream);
程序例:
#include <stdio.h>
int main(void)
{
FILE *fp;
char ch;
/* open a file for writing */
fp = fopen("DUMMY.FIL", "w");
/* force an error condition by attempting to read */
ch = fgetc(fp);
printf("%c\n",ch);
if (ferror(fp))
{
/* display an error message */
printf("Error reading from DUMMY.FIL\n");
/* reset the error and EOF indicators */
clearerr(fp);
}
fclose(fp);
return 0;
}
函数名: clearviewport
功 能: 清除图形视区
用 法: void far clearviewport(void);
程序例:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
#define CLIP_ON 1 /* activates clipping in viewport */
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int ht;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error occurred */
{
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1); /* terminate with an error code */
}
setcolor(getmaxcolor());
ht = textheight("W");
/* message in default full-screen viewport */
outtextxy(0, 0, "* <-- (0, 0) in default viewport");
/* create a smaller viewport */
setviewport(50, 50, getmaxx()-50, getmaxy()-50, CLIP_ON);
/* display some messages */
outtextxy(0, 0, "* <-- (0, 0) in smaller viewport");
outtextxy(0, 2*ht, "Press any key to clear viewport:");
/* wait for a key */
getch();
/* clear the viewport */
clearviewport();
/* output another message */
outtextxy(0, 0, "Press any key to quit:");
/* clean up */
getch();
closegraph();
return 0;
}
函数名: _close, close
功 能: 关闭文件句柄
用 法: int close(int handle);
程序例:
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
main()
{
int handle;
char buf[11] = "0123456789";
/* create a file containing 10 bytes */
handle = open("NEW.FIL", O_CREAT);
if (handle > -1)
{
write(handle, buf, strlen(buf));
/* close the file */
close(handle);
}
else
{
printf("Error opening file\n");
}
return 0;
}
函数名: clock
功 能: 确定处理器时间
用 法: clock_t clock(void);
程序例:
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
{
clock_t start, end;
start = clock();
delay(2000);
end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
return 0;
}
函数名: closegraph
功 能: 关闭图形系统
用 法: void far closegraph(void);
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 x, y;
/* initialize graphics mode */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk) /* an error
occurred */
{
printf("Graphics error: %s\n", grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1); /* terminate with an error code */
}
x = getmaxx() / 2;
y = getmaxy() / 2;
/* output a message */
settextjustify(CENTER_TEXT, CENTER_TEXT);
outtextxy(x, y, "Press a key to close the graphics system:");
/* wait for a key */
getch();
/* closes down the graphics system */
closegraph();
printf("We're now back in text mode.\n");
printf("Press any key to halt:");
getch();
return 0;
}
函数名: clreol
功 能: 在文本窗口中清除字符到行末
用 法: void clreol(void);
程序例:
#include <conio.h>
int main(void)
{
clrscr();
cprintf("The function CLREOL clears all characters from the\r\n");
cprintf("cursor position to the end of the line within the\r\n");
cprintf("current text window, without moving the cursor.\r\n");
cprintf("Press any key to continue . . .");
gotoxy(14, 4);
getch();
clreol();
getch();
return 0;
}
函数名: clrscr
功 能: 清除文本模式窗口
用 法: void clrscr(void);
程序例:
#include <conio.h>
int main(void)
{
int i;
clrscr();
for (i = 0; i < 20; i++)
cprintf("%d\r\n", i);
cprintf("\r\nPress any key to clear screen");
getch();
clrscr();
cprintf("The screen has been cleared!");
getch();
return 0;
}
函数名: coreleft
功 能: 返回未使用内存的大小
用 法: unsigned coreleft(void);
程序例:
#include <stdio.h>
#include <alloc.h>
int main(void)
{
printf("The difference between the highest allocated block and\n");
printf("the top of the heap is: %lu bytes\n", (unsigned long) coreleft());
return 0;
}
函数名: cos
功 能: 余弦函数
用 法: double cos(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double result;
double x = 0.5;
result = cos(x);
printf("The cosine of %lf is %lf\n", x, result);
return 0;
}
函数名: cosh
功 能: 双曲余弦函数
用 法: dluble cosh(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double result;
double x = 0.5;
result = cosh(x);
printf("The hyperboic cosine of %lf is %lf\n", x, result);
return 0;
}
函数名: country
功 能: 返回与国家有关的信息
用 法: struct COUNTRY *country(int countrycode, struct country *country);
程序例:
#include <dos.h>
#include <stdio.h>
#define USA 0
int main(void)
{
struct COUNTRY country_info;
country(USA, &country_info);
printf("The currency symbol for the USA is: %s\n",
country_info.co_curr);
return 0;
}
函数名: cprintf
功 能: 送格式化输出至屏幕
用 法: int cprintf(const char *format[, argument, ...]);
程序例:
#include <conio.h>
int main(void)
{
/* clear the screen */
clrscr();
/* create a text window */
window(10, 10, 80, 25);
/* output some text in the window */
cprintf("Hello world\r\n");
/* wait for a key */
getch();
return 0;
}
函数名: cputs
功 能: 写字符到屏幕
用 法: void cputs(const char *string);
程序例:
#include <conio.h>
int main(void)
{
/* clear the screen */
clrscr();
/* create a text window */
window(10, 10, 80, 25);
/* output some text in the window */
cputs("This is within the window\r\n");
/* wait for a key */
getch();
return 0;
}
函数名: _creat creat
功 能: 创建一个新文件或重写一个已存在的文件
用 法: int creat (const char *filename, int permiss);
程序例:
#include <sys\stat.h>
#include <string.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
char buf[11] = "0123456789";
/* change the default file mode from text to binary */
_fmode = O_BINARY;
/* create a binary file for reading and writing */
handle = creat("DUMMY.FIL", S_IREAD | S_IWRITE);
/* write 10 bytes to the file */
write(handle, buf, strlen(buf));
/* close the file */
close(handle);
return 0;
}
函数名: creatnew
功 能: 创建一个新文件
用 法: int creatnew(const char *filename, int attrib);
程序例:
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <dos.h>
#include <io.h>
int main(void)
{
int handle;
char buf[11] = "0123456789";
/* attempt to create a file that doesn't already exist */
handle = creatnew("DUMMY.FIL", 0);
if (handle == -1)
printf("DUMMY.FIL already exists.\n");
else
{
printf("DUMMY.FIL successfully created.\n");
write(handle, buf, strlen(buf));
close(handle);
}
return 0;
}
函数名: creattemp
功 能: 创建一个新文件或重写一个已存在的文件
用 法: int creattemp(const char *filename, int attrib);
程序例:
#include <string.h>
#include <stdio.h>
#include <io.h>
int main(void)
{
int handle;
char pathname[128];
strcpy(pathname, "\\");
/* create a unique file in the root directory */
handle = creattemp(pathname, 0);
printf("%s was the unique file created.\n", pathname);
close(handle);
return 0;
}
函数名: cscanf
功 能: 从控制台执行格式化输入
用 法: int cscanf(char *format[,argument, ...]);
程序例:
#include <conio.h>
int main(void)
{
char string[80];
/* clear the screen */
clrscr();
/* Prompt the user for input */
cprintf("Enter a string with no spaces:");
/* read the input */
cscanf("%s", string);
/* display what was read */
cprintf("\r\nThe string entered is: %s", string);
return 0;
}
函数名: ctime
功 能: 把日期和时间转换为字符串
用 法: char *ctime(const time_t *time);
程序例:
#include <stdio.h>
#include <time.h>
int main(void)
{
time_t t;
time(&t);
printf("Today's date and time: %s\n", ctime(&t));
return 0;
}
函数名: ctrlbrk
功 能: 设置Ctrl-Break处理程序
用 法: void ctrlbrk(*fptr)(void);
程序例:
#include <stdio.h>
#include <dos.h>
#define ABORT 0
int c_break(void)
{
printf("Control-Break pressed. Program aborting ...\n");
return (ABORT);
}
int main(void)
{
ctrlbrk(c_break);
for(;;)
{
printf("Looping... Press
}
return 0;
}
函数名: delay
功 能: 将程序的执行暂停一段时间(毫秒)
用 法: void delay(unsigned milliseconds);
程序例:
/* Emits a 440-Hz tone for 500 milliseconds */
#include <dos.h>
int main(void)
{
sound(440);
delay(500);
nosound();
return 0;
}
函数名: delline
功 能: 在文本窗口中删去一行
用 法: void delline(void);
程序例:
#include <conio.h>
int main(void)
{
clrscr();
cprintf("The function DELLINE deletes \
the line containing the\r\n");
cprintf("cursor and moves all lines \
below it one line up.\r\n");
cprintf("DELLINE operates within the \
currently active text\r\n");
cprintf("window. Press any key to \
continue . . .");
gotoxy(1,2); /* Move the cursor to the
second line and first column */
getch();
delline();
getch();
return 0;
}
函数名: detectgraph
功 能: 通过检测硬件确定图形驱动程序和模式
用 法: void far detectgraph(int far *graphdriver, int far *graphmode);
程序例:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
/* names of the various cards supported */
char *dname[] = { "requests detection",
"a CGA",
"an MCGA",
"an EGA",
"a 64K EGA",
"a monochrome EGA",
"an IBM 8514",
"a Hercules monochrome",
"an AT&T 6300 PC",
"a VGA",
"an IBM 3270 PC"
};
int main(void)
{
/* returns detected hardware info. */
int gdriver, gmode, errorcode;
/* detect graphics hardware available */
detectgraph(&gdriver, &gmode);
/* read result of detectgraph call */
errorcode = graphresult();
if (errorcode != grOk) /* an error
occurred */
{
printf("Graphics error: %s\n", \
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
exit(1); /* terminate with an error
code */
}
/* display the information detected */
clrscr();
printf("You have %s video display \
card.\n", dname[gdriver]);
printf("Press any key to halt:");
getch();
return 0;
}
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 <time.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>
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 <stdio.h>
#include <dos.h>
#include <conio.h>
#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;
}
函数名: div
功 能: 将两个整数相除, 返回商和余数
用 法: div_t (int number, int denom);
程序例:
#include <stdlib.h>
#include <stdio.h>
div_t x;
int main(void)
{
x = div(10,3);
printf("10 div 3 = %d remainder %d\n", x.quot, x.rem);
return 0;
}
函数名: dosexterr
功 能: 获取扩展DOS错误信息
用 法: int dosexterr(struct DOSERR *dblkp);
程序例:
#include <stdio.h>
#include <dos.h>
int main(void)
{
FILE *fp;
struct DOSERROR info;
fp = fopen("perror.dat","r");
if (!fp) perror("Unable to open file for
reading");
dosexterr(&info);
printf("Extended DOS error \
information:\n");
printf(" Extended error: \
%d\n",info.exterror);
printf("
Class: \
%x\n",info.class);
printf("
%x\n",info.action);
Action: \
printf(" Error Locus: \
%x\n",info.locus);
return 0;
}
函数名: dostounix
功 能: 转换日期和时间为UNIX时间格式
用 法: long dostounix(struct date *dateptr, struct time *timeptr);
程序例:
#include <time.h>
#include <stddef.h>
#include <dos.h>
#include <stdio.h>
int main(void)
{
time_t t;
struct time d_time;
struct date d_date;
struct tm *local;
getdate(&d_date);
gettime(&d_time);
t = dostounix(&d_date, &d_time);
local = localtime(&t);
printf("Time and Date: %s\n", \
asctime(local));
return 0;
}
函数名: drawpoly
功 能: 画多边形
用 法: void far drawpoly(int numpoints, int far *polypoints);
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 maxx, maxy;
/* our polygon array */
int poly[10];
/* initialize graphics and local
variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk)
/* an error occurred */
{
printf("Graphics error: %s\n", \
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
/* terminate with an error code */
exit(1);
}
maxx = getmaxx();
maxy = getmaxy();
poly[0] = 20;
poly[1] = maxy / 2;
/* 1st vertext */
poly[2] = maxx - 20; /* 2nd */
poly[3] = 20;
poly[4] = maxx - 50; /* 3rd */
poly[5] = maxy - 20;
poly[6] = maxx / 2; /* 4th */
poly[7] = maxy / 2;
/*
*/
drawpoly doesn't automatically close
the polygon, so we close it.
poly[8] = poly[0];
poly[9] = poly[1];
/* draw the polygon */
drawpoly(5, poly);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: dup
功 能: 复制一个文件句柄
用 法: int dup(int handle);
程序例:
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <io.h>
void flush(FILE *stream);
int main(void)
{
FILE *fp;
char msg[] = "This is a test";
/* create a file */
fp = fopen("DUMMY.FIL", "w");
/* write some data to the file */
fwrite(msg, strlen(msg), 1, fp);
clrscr();
printf("Press any key to flush \
DUMMY.FIL:");
getch();
/* flush the data to DUMMY.FIL without
closing it */
flush(fp);
printf("\nFile was flushed, Press any \
key to quit:");
getch();
return 0;
}
void flush(FILE *stream)
{
int duphandle;
/* flush TC's internal buffer */
fflush(stream);
/* make a duplicate file handle */
duphandle = dup(fileno(stream));
/* close the duplicate handle to flush the
DOS buffer */
close(duphandle);
}
函数名: dup2
功 能: 复制文件句柄
用 法: int dup2(int oldhandle, int newhandle);
程序例:
#include <sys\stat.h>
#include <string.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
#define STDOUT 1
int nul, oldstdout;
char msg[] = "This is a test";
/* create a file */
nul = open("DUMMY.FIL", O_CREAT | O_RDWR,
S_IREAD | S_IWRITE);
/* create a duplicate handle for standard
output */
oldstdout = dup(STDOUT);
/*
redirect standard output to DUMMY.FIL
by duplicating the file handle onto the
file handle for standard output.
*/
dup2(nul, STDOUT);
/* close the handle for DUMMY.FIL */
close(nul);
/* will be redirected into DUMMY.FIL */
write(STDOUT, msg, strlen(msg));
/* restore original standard output
handle */
dup2(oldstdout, STDOUT);
/* close duplicate handle for STDOUT */
close(oldstdout);
return 0;
}
函数名: ecvt
功 能: 把一个浮点数转换为字符串
用 法: char ecvt(double value, int ndigit, int *decpt, int *sign);
程序例:
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
char *string;
double value;
int dec, sign;
int ndig = 10;
clrscr();
value = 9.876;
string = ecvt(value, ndig, &dec, &sign);
printf("string = %s
dec = %d \
sign = %d\n", string, dec, sign);
value = -123.45;
ndig= 15;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d sign = %d\n",
string, dec, sign);
value = 0.6789e5; /* scientific
notation */
ndig = 5;
string = ecvt(value,ndig,&dec,&sign);
printf("string = %s dec = %d\
sign = %d\n", string, dec, sign);
return 0;
}
函数名: ellipse
功 能: 画一椭圆
用 法: void far ellipse(int x, int y, int stangle, int endangle,
int xradius, int yradius);
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 = 0, endangle = 360;
int xradius = 100, yradius = 50;
/* initialize graphics, local variables */
initgraph(&gdriver, &gmode, "");
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk)
/* an error occurred */
{
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 ellipse */
ellipse(midx, midy, stangle, endangle,
xradius, yradius);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: enable
功 能: 开放硬件中断
用 法: void enable(void);
程序例:
/* ** NOTE:
This is an interrupt service routine. You can NOT compile this program
with Test Stack Overflow turned on and get an executable file which will
operate correctly.
*/
#include <stdio.h>
#include <dos.h>
#include <conio.h>
/* The clock tick interrupt */
#define INTR 0X1C
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++;
/*
re enable 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;
}
函数名: eof
功 能: 检测文件结束
用 法: int eof(int *handle);
程序例:
#include <sys\stat.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
char msg[] = "This is a test";
char ch;
/* create a file */
handle = open("DUMMY.FIL",
O_CREAT | O_RDWR,
S_IREAD | S_IWRITE);
/* write some data to the file */
write(handle, msg, strlen(msg));
/* seek to the beginning of the file */
lseek(handle, 0L, SEEK_SET);
/*
reads chars from the file until hit EOF
*/
do
{
read(handle, &ch, 1);
printf("%c", ch);
} while (!eof(handle));
close(handle);
return 0;
}
函数名: exec...
功 能: 装入并运行其它程序的函数
用 法: int execl(char *pathname, char *arg0, arg1, ..., argn, NULL);
int execle(char *pathname, char *arg0, arg1, ..., argn, NULL,
char *envp[]);
int execlp(char *pathname, char *arg0, arg1, .., NULL);
int execple(char *pathname, char *arg0, arg1, ..., NULL,
char *envp[]);
int execv(char *pathname, char *argv[]);
int execve(char *pathname, char *argv[], char *envp[]);
int execvp(char *pathname, char *argv[]);
int execvpe(char *pathname, char *argv[], char *envp[]);
程序例:
/* execv example */
#include <process.h>
#include <stdio.h>
#include <errno.h>
void main(int argc, char *argv[])
{
int i;
printf("Command line arguments:\n");
for (i=0; i<argc; i++)
printf("[%2d] : %s\n", i, argv[i]);
printf("About to exec child with arg1 arg2 ...\n");
execv("CHILD.EXE", argv);
perror("exec error");
exit(1);
}
函数名: exit
功 能: 终止程序
用 法: void exit(int status);
程序例:
#include <stdlib.h>
#include <conio.h>
#include <stdio.h>
int main(void)
{
int status;
printf("Enter either 1 or 2\n");
status = getch();
/* Sets DOS errorlevel */
exit(status - '0');
/* Note: this line is never reached */
return 0;
}
函数名: exp
功 能: 指数函数
用 法: double exp(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double result;
double x = 4.0;
result = exp(x);
printf("'e' raised to the power \
of %lf (e ^ %lf) = %lf\n",
x, x, result);
return 0;
}
目录
目录
Null's Notebook
函数名: fabs
功 能: 返回浮点数的绝对值
用 法: double fabs(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
float number = -1234.0;
printf("number: %f absolute value: %f\n",
number, fabs(number));
return 0;
}
函数名: farcalloc
功 能: 从远堆栈中申请空间
用 法: void far *farcalloc(unsigned long units, unsigned ling unitsz);
程序例:
#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
/*
Note: movedata is used because you
might be in a small data model, in
which case a normal string copy routine
can not be used since it assumes the
pointer size is near.
*/
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farcoreleft
功 能: 返回远堆中未作用存储区大小
用 法: long farcoreleft(void);
程序例:
#include <stdio.h>
#include <alloc.h>
int main(void)
{
printf("The difference between the\
highest allocated block in the\
far\n");
printf("heap and the top of the far heap\
is: %lu bytes\n", farcoreleft());
return 0;
}
函数名: farfree
功 能: 从远堆中释放一块
用 法: void farfree(void);
程序例:
#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farcalloc(10, sizeof(char));
/* copy "Hello" into allocated memory */
/*
Note: movedata is used because you might be in a small data model,
in which case a normal string copy routine can't be used since it
assumes the pointer size is near.
*/
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farmalloc
功 能: 从远堆中分配存储块
用 法: void far *farmalloc(unsigned long size);
程序例:
#include <stdio.h>
#include <alloc.h>
#include <string.h>
#include <dos.h>
int main(void)
{
char far *fptr;
char *str = "Hello";
/* allocate memory for the far pointer */
fptr = farmalloc(10);
/* copy "Hello" into allocated memory */
/*
Note: movedata is used because we might
be in a small data model, in which case
a normal string copy routine can not be
used since it assumes the pointer size
is near.
*/
movedata(FP_SEG(str), FP_OFF(str),
FP_SEG(fptr), FP_OFF(fptr),
strlen(str));
/* display string (note the F modifier) */
printf("Far string is: %Fs\n", fptr);
/* free the memory */
farfree(fptr);
return 0;
}
函数名: farrealloc
功 能: 调整远堆中的分配块
用 法: void far *farrealloc(void far *block, unsigned long newsize);
程序例:
#include <stdio.h>
#include <alloc.h>
int main(void)
{
char far *fptr;
fptr = farmalloc(10);
printf("First address: %Fp\n", fptr);
fptr = farrealloc(fptr,20);
printf("New address : %Fp\n", fptr);
farfree(fptr);
return 0;
}