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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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