函数名: tan
功 能: 正切函数
用 法: double tan(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double result, x;
x = 0.5;
result = tan(x);
printf("The tan of %lf is %lf\n", x, result);
return 0;
}
函数名: tanh
功 能: 双曲正切函数
用 法: double tanh(double x);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double result, x;
x = 0.5;
result = tanh(x);
printf("The hyperbolic tangent of %lf is %lf\n", x, result);
return 0;
}
函数名: tell
功 能: 取文件指针的当前位置
用 法: long tell(int handle);
程序例:
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
char msg[] = "Hello world";
if ((handle = open("TEST.$$$", O_CREAT | O_TEXT | O_APPEND)) == -1)
{
perror("Error:");
return 1;
}
write(handle, msg, strlen(msg));
printf("The file pointer is at byte %ld\n", tell(handle));
close(handle);
return 0;
}
函数名: textattr
功 能: 设置文本属性
用 法: void textattr(int attribute);
程序例:
#include <conio.h>
int main(void)
{
int i;
clrscr();
for (i=0; i<9; i++)
{
textattr(i + ((i+1) << 4));
cprintf("This is a test\r\n");
}
return 0;
}
函数名: textbackground
功 能: 选择新的文本背景颜色
用 法: void textbackground(int color);
程序例:
#include <conio.h>
int main(void)
{
int i, j;
clrscr();
for (i=0; i<9; i++)
{
for (j=0; j<80; j++)
cprintf("C");
cprintf("\r\n");
textcolor(i+1);
textbackground(i);
}
return 0;
}
函数名: textcolor
功 能: 在文本模式中选择新的字符颜色
用 法: void textcolor(int color);
程序例:
#include <conio.h>
int main(void)
{
int i;
for (i=0; i<15; i++)
{
textcolor(i);
cprintf("Foreground Color\r\n");
}
return 0;
}
函数名: textheight
功 能: 返回以像素为单位的字符串高度
用 法: int far textheight(char far *textstring);
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 y = 0;
int i;
char msg[80];
/* 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 */
}
/* draw some text on the screen */
for (i=1; i<11; i++)
{
/* select the text style, direction, and size */
settextstyle(TRIPLEX_FONT, HORIZ_DIR, i);
/* create a message string */
sprintf(msg, "Size: %d", i);
/* output the message */
outtextxy(1, y, msg);
/* advance to the next text line */
y += textheight(msg);
}
/* clean up */
getch();
closegraph();
return 0;
}
函数名: textmode
功 能: 将屏幕设置成文本模式
用 法: void textmode(int mode);
程序例:
#include <conio.h>
int main(void)
{
textmode(BW40);
cprintf("ABC");
getch();
textmode(C40);
cprintf("ABC");
getch();
textmode(BW80);
cprintf("ABC");
getch();
textmode(C80);
cprintf("ABC");
getch();
textmode(MONO);
cprintf("ABC");
getch();
return 0;
}
函数名: textwidth
功 能: 返回以像素为单位的字符串宽度
用 法: int far textwidth(char far *textstring);
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 = 0, y = 0;
int i;
char msg[80];
/* 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 */
}
y = getmaxy() / 2;
settextjustify(LEFT_TEXT, CENTER_TEXT);
for (i=1; i<11; i++)
{
/* select the text style, direction, and size */
settextstyle(TRIPLEX_FONT, HORIZ_DIR, i);
/* create a message string */
sprintf(msg, "Size: %d", i);
/* output the message */
outtextxy(x, y, msg);
/* advance to the end of the text */
x += textwidth(msg);
}
/* clean up */
getch();
closegraph();
return 0;
}
函数名: time
功 能: 取一天的时间
用 法: logn time(long *tloc);
程序例:
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
{
time_t t;
t = time(NULL);
printf("The number of seconds since January 1, 1970 is %ld",t);
return 0;
}
函数名: tmpfile
功 能: 以二进制方式打开暂存文件
用 法: FILE *tmpfile(void);
程序例:
#include <stdio.h>
#include <process.h>
int main(void)
{
FILE *tempfp;
tempfp = tmpfile();
if (tempfp)
printf("Temporary file created\n");
else
{
printf("Unable to create temporary file\n");
exit(1);
}
return 0;
}
函数名: tmpnam
功 能: 创建一个唯一的文件名
用 法: char *tmpnam(char *sptr);
程序例:
#include <stdio.h>
int main(void)
{
char name[13];
tmpnam(name);
printf("Temporary name: %s\n", name);
return 0;
}
函数名: tolower
功 能: 把字符转换成小写字母
用 法: int tolower(int c);
程序例:
#include <string.h>
#include <stdio.h>
#include <ctype.h>
int main(void)
{
int length, i;
char *string = "THIS IS A STRING";
length = strlen(string);
for (i=0; i<length; i++)
{
string[i] = tolower(string[i]);
}
printf("%s\n",string);
return 0;
}
函数名: toupper
功 能: 把字符转换成大写字母
用 法: int toupper(int c);
程序例:
#include <string.h>
#include <stdio.h>
#include <ctype.h>
int main(void)
{
int length, i;
char *string = "this is a string";
length = strlen(string);
for (i=0; i<length; i++)
{
string[i] = toupper(string[i]);
}
printf("%s\n",string);
return 0;
}
函数名: tzset
功 能: UNIX时间兼容函数
用 法: void tzset(void);
程序例:
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
time_t td;
putenv("TZ=PST8PDT");
tzset();
time(&td);
printf("Current time = %s\n", asctime(localtime(&td)));
return 0;
}
函数名: ultoa
功 能: 转换一个无符号长整型数为字符串
用 法: char *ultoa(unsigned long value, char *string, int radix);
程序例:
#include <stdlib.h>
#include <stdio.h>
int main( void )
{
unsigned long lnumber = 3123456789L;
char string[25];
ultoa(lnumber,string,10);
printf("string = %s unsigned long = %lu\n",string,lnumber);
return 0;
}
函数名: ungetc
功 能: 把一个字符退回到输入流中
用 法: int ungetc(char c, FILE *stream);
程序例:
#include <stdio.h>
#include <ctype.h>
int main( void )
{
int i=0;
char ch;
puts("Input an integer followed by a char:");
/* read chars until non digit or EOF */
while((ch = getchar()) != EOF && isdigit(ch))
i = 10 * i + ch - 48; /* convert ASCII into int value */
/* if non digit char was read, push it back into input buffer */
if (ch != EOF)
ungetc(ch, stdin);
printf("i = %d, next char in buffer = %c\n", i, getchar());
return 0;
}
函数名: ungetch
功 能: 把一个字符退回到键盘缓冲区中
用 法: int ungetch(int c);
程序例:
#include <stdio.h>
#include <ctype.h>
#include <conio.h>
int main( void )
{
int i=0;
char ch;
puts("Input an integer followed by a char:");
/* read chars until non digit or EOF */
while((ch = getche()) != EOF && isdigit(ch))
i = 10 * i + ch - 48; /* convert ASCII into int value */
/* if non digit char was read, push it back into input buffer */
if (ch != EOF)
ungetch(ch);
printf("\n\ni = %d, next char in buffer = %c\n", i, getch());
return 0;
}
函数名: unixtodos
功 能: 把日期和时间转换成DOS格式
用 法: void unixtodos(long utime, struct date *dateptr,
struct time *timeptr);
程序例:
#include <stdio.h>
#include <dos.h>
char *month[] = {"---", "Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
#define SECONDS_PER_DAY 86400L /* the number of seconds in one day */
struct date dt;
struct time tm;
int main(void)
{
unsigned long val;
/* get today's date and time */
getdate(&dt);
gettime(&tm);
printf("today is %d %s %d\n", dt.da_day, month[dt.da_mon], dt.da_year);
/* convert date and time to unix format (number of seconds since Jan 1, 1970 */
val = dostounix(&dt, &tm);
/* subtract 42 days worth of seconds */
val -= (SECONDS_PER_DAY * 42);
/* convert back to dos time and date */
unixtodos(val, &dt, &tm);
printf("42 days ago it was %d %s %d\n",
dt.da_day, month[dt.da_mon], dt.da_year);
return 0;
}
函数名: unlink
功 能: 删掉一个文件
用 法: int unlink(char *filename);
程序例:
#include <stdio.h>
#include <io.h>
int main(void)
{
FILE *fp = fopen("junk.jnk","w");
int status;
fprintf(fp,"junk");
status = access("junk.jnk",0);
if (status == 0)
printf("File exists\n");
else
printf("File doesn't exist\n");
fclose(fp);
unlink("junk.jnk");
status = access("junk.jnk",0);
if (status == 0)
printf("File exists\n");
else
printf("File doesn't exist\n");
return 0;
}
函数名: unlock
功 能: 解除文件共享锁
用 法: int unlock(int handle, long offset, long length);
程序例:
#include <io.h>
#include <fcntl.h>
#include <sys\stat.h>
#include <process.h>
#include <share.h>
#include <stdio.h>
int main(void)
{
int handle, status;
long length;
handle = sopen("c:\\autoexec.bat",O_RDONLY,SH_DENYNO,S_IREAD);
if (handle < 0)
{
printf("sopen failed\n");
exit(1);
}
length = filelength(handle);
status = lock(handle,0L,length/2);
if (status == 0)
printf("lock succeeded\n");
else
printf("lock failed\n");
status = unlock(handle,0L,length/2);
if (status == 0)
printf("unlock succeeded\n");
else
printf("unlock failed\n");
close(handle);
return 0;
}
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