C语言库函数(G类字母)1

C语言库函数(G类字母)1


函数名: gcvt
功 能: 把浮点数转换成字符串
用 法: char *gcvt(double value, int ndigit, char *buf);
程序例:
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
char str[25];
double num;
int sig = 5; /* significant digits */

/* a regular number */
num = 9.876;
gcvt(num, sig, str);
printf("string = %s\n", str);

/* a negative number */
num = -123.4567;
gcvt(num, sig, str);
printf("string = %s\n", str);

/* scientific notation */
num = 0.678e5;
gcvt(num, sig, str);
printf("string = %s\n", str);

return(0);
}




函数名: geninterrupt
功 能: 产生一个软中断
用 法: void geninterrupt(int intr_num);
程序例:

#include <conio.h>
#include <dos.h>

/* function prototype */
void writechar(char ch);

int main(void)
{
clrscr();
gotoxy(80,25);
writechar('*');
getch();
return 0;
}

/*
outputs a character at the current cursor
position using the video BIOS to avoid the
scrolling of the screen when writing to
location (80,25).
*/

void writechar(char ch)
{
struct text_info ti;
/* grab current text settings */
gettextinfo(&ti);
/* interrupt 0x10 sub-function 9 */
_AH = 9;
/* character to be output */
_AL = ch;
_BH = 0; /* video page */
_BL = ti.attribute; /* video attribute */
_CX = 1; /* repetition factor */
geninterrupt(0x10); /* output the char */
}



函数名: getarccoords
功 能: 取得最后一次调用arc的坐标
用 法: void far getarccoords(struct arccoordstype far *arccoords);
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;
struct arccoordstype arcinfo;
int midx, midy;
int stangle = 45, endangle = 270;
char sstr[80], estr[80];

/* 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();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;

/* draw arc and get coordinates */
setcolor(getmaxcolor());
arc(midx, midy, stangle, endangle, 100);
getarccoords(&arcinfo);

/* convert arc information into strings */
sprintf(sstr, "*- (%d, %d)",
arcinfo.xstart, arcinfo.ystart);
sprintf(estr, "*- (%d, %d)",
arcinfo.xend, arcinfo.yend);

/* output the arc information */
outtextxy(arcinfo.xstart,
arcinfo.ystart, sstr);
outtextxy(arcinfo.xend,
arcinfo.yend, estr);

/* clean up */
getch();
closegraph();
return 0;
}




函数名: getaspectratio
功 能: 返回当前图形模式的纵横比
用 法: void far getaspectratio(int far *xasp, int far *yasp);
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 xasp, yasp, midx, midy;

/* 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();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());

/* get current aspect ratio settings */
getaspectratio(&xasp, &yasp);

/* draw normal circle */
circle(midx, midy, 100);
getch();

/* draw wide circle */
cleardevice();
setaspectratio(xasp/2, yasp);
circle(midx, midy, 100);
getch();

/* draw narrow circle */
cleardevice();
setaspectratio(xasp, yasp/2);
circle(midx, midy, 100);

/* clean up */
getch();
closegraph();
return 0;
}




函数名: getbkcolor
功 能: 返回当前背景颜色
用 法: int far getbkcolor(void);
程序例:

#include <graphics.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int bkcolor, midx, midy;
char bkname[35];

/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");

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