c语言的用法
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语言程序设计是一门基础的程序设计语言,学好这门课对以后程序开发至关重要。由于C语言灵活、强大,初学者要全面地掌握它非常吃力,因此在学习C语言的过程中,但一定要熟练掌握C语言的流程控制语句、数组、函数、指针等基础知识的应用,为学习面向对象程序设计打下坚实的基础。下面小编就为大家来介绍下c语言的用法。
c语言的用法: 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 */
}
c语言的用法: 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: %dn", number, abs(number));
return 0;
}
c语言的用法: 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 keyn");
getch();
sector = 0;
if (absread(0, 1, sector, &buf) != 0)
{
perror("Disk problem");
exit(1);
}
printf("Read OKn");
strt = 3;
for (i=0; i<80; i++)
{
ch_out = buf[strt+i];
putchar(ch_out);
}
printf("n");
return(0);
}
c语言的用法: 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: %sn",
file_exists("NOTEXISTS.FIL") ? "YES" : "NO");
return 0;
}
int file_exists(char *filename)
{
return (access(filename, 0) == 0);
}
c语言的用法: acos
功 能: 反余弦c语言的用法
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 %lfn", x, result);
return 0;
}
c语言的用法: 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: %xn", segp);
else
printf("Failed: maximum number of paragraphs available is %un",
stat);
return 0;
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: 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("%sn", str);
return 0;
}
c语言的用法: asin
功 能: 反正弦c语言的用法
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 %lfn", x, result);
return(0);
}
c语言的用法: 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;
}
c语言的用法: atan
功 能: 反正切c语言的用法
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 %lfn", x, result);
return(0);
}
c语言的用法: 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 %lfn", (y / x), result);
return 0;
}
c语言的用法: atexit
功 能: 注册终止c语言的用法
用 法: int atexit(atexit_t func);
程序例:
#include <stdio.h>
#include <stdlib.h>
void exit_fn1(void)
{
printf("Exit function #1 calledn");
}
void exit_fn2(void)
{
printf("Exit function #2 calledn");
}
int main(void)
{
/* post exit function #1 */
atexit(exit_fn1);
/* post exit function #2 */
atexit(exit_fn2);
return 0;
}
c语言的用法: 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 = %fn", str, f);
return 0;
}
c语言的用法: 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 = %dn", str, n);
return 0;
}
c语言的用法: 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 = %ldn", str, l);
return(0);
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: 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 topflag);
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: %sn", 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;
}
c语言的用法: 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;
}
c语言的用法: 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 directoryn");
gets(buffer);
test = bdosptr(0x3B,buffer,0);
if(test)
{
printf("DOS error message: %dn", errno);
/* See errno.h for error listings */
exit (1);
}
getcwd(buffer, BUFLEN);
printf("The current directory is: %sn", buffer);
return 0;
}
c语言的用法: 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 0
#define DATA_READY 0x100
#define TRUE 1
#define FALSE 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;
}
c语言的用法: 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 readyn");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Readyn")) :
(printf("Drive A: Not Readyn"));
return 0;
}
c语言的用法: 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 readyn");
result = biosdisk(4,0,0,0,0,1,buffer);
result &= 0x02;
(result) ? (printf("Drive A: Readyn")) :
(printf("Drive A: Not Readyn"));
return 0;
}
c语言的用法: 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("%#02xn", key);
return 0;
}
c语言的用法: 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 = %dKn",memory_size);
return 0;
}
c语言的用法: 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 continuen");
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;
}
c语言的用法: 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:rn");
cprintf("The number of seconds since midnight is:rn");
cprintf("The number of minutes since midnight is:rn");
cprintf("The number of hours since midnight is:rn");
cprintf("rnPress 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;
}
c语言的用法: 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 freen", coreleft());
brk(ptr+1000);
printf(" After brk() call: %lu bytes freen", coreleft());
return 0;
}
c语言的用法: bsearch
功 能: 二分法搜索
用 法: void *bsearch(const void *key, const void *base, size_t *nelem,
size_t width, int(*fcmp)(const void *, const *));
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;
}
c语言的用法: 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;
}
c语言的用法: 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 %sn", str);
/* free memory */
free(str);
return 0;
}
c语言的用法: 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 %5.2lfn", number);
printf("number rounded down %5.2lfn", down);
printf("number rounded up %5.2lfn", up);
return 0;
}
c语言的用法: 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 %pn", 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 %pn", p, &buffer);
return 0;
}
c语言的用法: 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: \%sn", old_dir);
if (chdir("\"))
{
perror("chdir()");
exit(1);
}
if (getcurdir(0, new_dir))
{
perror("getcurdir()");
exit(1);
}
printf("Current directory is now: \%sn", new_dir);
printf("nChanging back to orignal directory: \%sn", old_dir);
if (chdir(old_dir))
{
perror("chdir()");
exit(1);
}
return 0;
}
c语言的用法: _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 <sysstat.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-onlyn", filename);
else
printf("Made %s read-onlyn", filename);
}
c语言的用法: 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;
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: 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("%cn",ch);
if (ferror(fp))
{
/* display an error message */
printf("Error reading from DUMMY.FILn");
/* reset the error and EOF indicators */
clearerr(fp);
}
fclose(fp);
return 0;
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: _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 filen");
}
return 0;
}
c语言的用法: 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: %fn", (end - start) / CLK_TCK);
return 0;
}
c语言的用法: 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: %sn", 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;
}
c语言的用法: 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 thern");
cprintf("cursor position to the end of the line within thern");
cprintf("current text window, without moving the cursor.rn");
cprintf("Press any key to continue . . .");
gotoxy(14, 4);
getch();
clreol();
getch();
return 0;
}
c语言的用法: 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("%drn", i);
cprintf("rnPress any key to clear screen");
getch();
clrscr();
cprintf("The screen has been cleared!");
getch();
return 0;
}
c语言的用法: 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 andn");
printf("the top of the heap is: %lu bytesn", (unsigned long) coreleft());
return 0;
}
c语言的用法: cos
功 能: 余弦c语言的用法
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 %lfn", x, result);
return 0;
}
c语言的用法: cosh
功 能: 双曲余弦c语言的用法
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 %lfn", x, result);
return 0;
}
c语言的用法: 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: %sn",
country_info.co_curr);
return 0;
}
c语言的用法: 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 worldrn");
/* wait for a key */
getch();
return 0;
}
c语言的用法: 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 windowrn");
/* wait for a key */
getch();
return 0;
}
c语言的用法: _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 <sysstat.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;
}
c语言的用法: 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;
}
c语言的用法: 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;
}
c语言的用法: 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("rnThe string entered is: %s", string);
return 0;
}
c语言的用法: 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: %sn", ctime(&t));
return 0;
}
c语言的用法: 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 <Ctrl-Break> to quit:n");
}
return 0;
}