101 ways to mess up your computer

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#07: Compile and run this program in Visual Studio 2008:

It causes your computer to emit a constant beeping sound while using up massive system resources. Only known remedy is shutting down the system. ^^v

It was supposed to only beep a set number of times, but thanks to an unexpected bug it wouldn't stop. Can any programmers here spot the bug?

oh there are more then 101 ways

FLASHPLAYER JUST DID IT AGAIN!

NUKEWAR!

NETWORK DISCONNECT IN 3...2...1...ETX

... which would have been reported as a warning by your compiler, if ypu were using a sensible compiler, and had warnings turned on. (Constant expression used as loop termination condition.)

Really? That's curious. I'll have to ask Jerry* about that.

*Professor Hamann, my Computer Science instructor and head of the CoSci department at UW's College of Engineering.

At any rate, I fixed it so that it only beeps for the number of times you specify it to (the "annoyance level") plus one for good luck:

//Annoying Program
//Guaranteed to annoy you to kingdom come.

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

const char b = 7;

int main()
{
char a;
int iquit;
cout << "Welcome to the most annoying computer program ever." << endl;
cout << "Enter annoyance level." << endl;
cin >> iquit;
cout << "Press 'a' to annoy." << endl;
cin >> a;
while(a == 'a') {
for(int i = 0; i <= iquit; i++) {
cout << b;
}
cout << "Press 'a' to annoy." << endl;
cin >> a;
a = a != 'a' ? 'a' : 'b';
}
return 0;
}

I can spot the bug!

You are running Microsoft Windows.

That aside, you don't read a new value for the variable a while inside the loop, so the variable a always == 'a', and the loop is infinite.

Cue infinite buzz.

And... you are right. I did look again, and even with a better compiler (gcc), there was no warning. The bug is indeed subtle, in this case.

Your code combined the decision whether to initiate an infinite loop with the same test (on a non-volatile location) being used to maintain that loop. It's something a compiler could spot as unlikely to be what was intended. I'm all in favour of intelligent compilers.

This bug is related to why I dislike (and won't use) the "while(TRUE)" sort of infinite loop: because it relies on an optimiser to remove the test. I always use "for (;;)" - which explicitly shows that no test is present. It comes from a lot of embedded coding... and I don't mean the modern sort of embedded - I mean the sort where you are lucky to count your code space in kilobytes. (Oh... and ALL the compilers were utter rubbish and they could be relied on to regularly produce completely wrong object code.)

I just typed CTRL/C. Why would I want to do anything more drastic?

Correction: Only known remedy for those who don't know Command Prompt shortcuts.

C++? Yuck!

Anyway, you could do the beeping thing in pretty much any programming language that has ASCII escape sequences:

Here's the same thing, without programming.
Make sure your speaker's on.
Lay something heavy on the keyboard.
Wait...

Have a hot drink beside your computer, and don't watch what you're doing, when you stand up.

A few from my highlights reel of computer killage:

* Plug an old hard drive (laptop drive) into the cable 1 pin off. Watch the controller smoke when the computer is turned on.

* Stick (accidentally) a screwdriver into the power supply cooling fan, causing it to short, resulting in the entire power supply overloading and burning out.

* In high school I wrote a machine code program (6502) that would tic the speaker -- only way to stop it was a reset.

Your sig:

anahl nathrak, uth vas bethude, doth yel dyenvey...

Thats from an old Arthur movie right?. Its a spell spoken by Merlin.
I have remembered those lines for decades ever since I first saw that movie!