They usually use a linux distro...
And have a direct remote connection to the server, with the applet etc directly from the server (atleast that's how TCS Ion does it, they use a free to use, very lightwieght linux distro, with remote connection to the server, which then loads the mozilla applet (b/c again free to use commercially) in which you give the exam). I presume Bitsat would be on the same lines....
document.onkeydown = function ()
var ev = event.keyCode;
// if (ev==116 || ev==8 || ev==18)
This is one that the official mock application of bitsat uses