C Program to create Captcha

by Subramanian 2012-09-10 14:23:51

This program generates captcha, a captcha is a random code generated using some algorithm. We will use random function in our code. These are used in typing tutors and in website to check whether a human is operating on a website.



#include<stdlib.h>
#include<dos.h>
#include<graphics.h>

main()
{
int i = 0, key, num, midx, gd = DETECT, gm;
char a[10];

initgraph(&gd,&gm,"C:\\TC\\BGI");

midx = getmaxx()/2;

settextstyle(SCRIPT_FONT,HORIZ_DIR,5);
settextjustify(CENTER_TEXT,CENTER_TEXT);
setcolor(GREEN);
outtextxy(midx,20,"CAPTCHA");
settextstyle(SCRIPT_FONT,HORIZ_DIR,2);
outtextxy(midx,125,"Press any key to change the generated random code \"captcha\"");
outtextxy(midx,150,"Press escape key to exit...");

setcolor(WHITE);
setviewport(100,200,600,400,1);
setcolor(RED);
randomize();

while(1)
{
while(i<6)
{
num = random(3);

if ( num == 0 )
a[i] = 65 + random(26); /* 65 is the ASCII value of A */
else if ( num == 1)
a[i] = 97 + random(26); /* 97 is the ASCII value of a */
else
a[i] = 48 + random(10); /* 48 is the ASCII value of 0 */
i++;
}
a[i] = '\0';
outtextxy(210,100,a);
key = getch();

if( key == 27 ) /* escape key*/
exit(0);
clearviewport();
i = 0;
}
}


Output of program:
captcha.PNG
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