IT PRO: Blogs: Dave F: 2009 May

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How to be a Guitar Hero

Posted in Open Source Software, the web, music, e-commerce on May 29, 2009 at 3:04 pm

I think I’ve blogged in the past about how easy learning guitar is these days. What with cheap guitars actually being playable, tuners meaning you can get the thing in tune and the usual explosion of multimedia resources with the web being in the lead (especially for free stuff) things are a lot better than in my young day.

However, a real boon is to see a (musical) score and have it played, the notes lighting up as they are sound - how many times have I looked at a sheet of music, listened to the records (sorry CD) and not been able to join the two together?

Power tab is a freebie that does just that. I tried it a while back but due to the vagaries of my PC, the sound was always a beat behind - having the note that isn’t being played highlighted just doesn’t help!

I have therefore coughed up some cash (£50!!!) to buy Guitar Pro 5 which not only does the highlight as it plays it also shows the stave (lines and dots) as well as the tab, and plays multiple instruments (including drums) which you can solo / mute like a multitrack desk. You can also use it to score your own work and all sorts of stuff (I haven’t read the manual - obviously). I’m not on commission but as you don’t know that you don’t have to take my word for it - you can download a trial version http://www.guitar-pro.com/en/index.php and check the Amazon reviews http://www.amazon.co.uk/Arobas-Music-Guitar-Pro-PC/dp/3938259108

Most of the music seems to be “own work” ie people have figured it out themselves and uploaded what they think is happening to the net so you take your chances trusting any given arrangement. Also I’m just using a standard midi and it doesn’t sound great, in fact “pants” might be a better word. If I’m being picky the speed option could be a nice slider not just a half, quater etc speed - but as I said I haven’t RTFM’ed yet.

So between you tube, tab sites and my new toy I might learn a few tunes yet!

And £50? Better spent than on some Guitar Hero game.

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Ashes to Ashes, DOS to DOS

By Dave F in Reader

Posted in In the news, media, Microsoft on May 20, 2009 at 9:59 am

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What is more irritating than young people talking about the “your” old times? Over at http://tech.uk.msn.com/features/gallery.aspx?cp-documentid=147411818

someone seems to be out of there pension zone.

Actually it’s not too bad an article but monochrome monitors were different to colour monitors and you can’t get them any more. You may get colour monitors that only display in two colours but they aren’t the same thing! The old mono monitors had a separate interface. I know because I used to write a twin headed DOS application and the only way to do it was using a standard colour monitor and a mono monitor as they used different address spaces. For the mono you wrote ASCII directly into the adaptors memory and it rendered it into a very nice sharp font. The fact you couldn’t get them any more was part of the death of the product.

As for DOS - don’t most of us use a command line windows prompt everyday? OK, maybe not most of us but plenty of us do. And Windows 95 sat on top of DOS, everyone knows that (well quite few people claimed it did).

Is it coincidence that yesterday I was trashing floppies, looking at ZIP drives, using my PDA, typing at a “DOS” prompt and discussing dial up modems with my neighbour?

I expect the author was one of the consultants to Ashes to Ashes - in my 1980’s we didn’t have trendy concealed lighting, bay trees, constatntly visible bra straps, …

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Floppies must die, but how?

By Dave F in Reader

Posted in Freecycle, Security on May 19, 2009 at 5:57 pm

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I don’t believe this. I spent years carefully keeping floppy disks away from magnetic fields - “Ooo you mustn’t put them near the monitor, Ooo careful of that fridge magnet,…”

I have a pile of them to get rid of, I’d like to freecycle them but I would have to be sure they have been cleaned. As an experiment I just rubbed one with my sons zoids (zings? before you call social services check the video http://www.youtube.com/watch?v=VR-gjYdbebE&feature=related) and the damn thing is as happy as Larry.

The last load of floppies I binned were all 5.25″ and I literally pulled them apart, wrenching the magnetic disk out of the cover. I have a about 60 3.5″ disks plus a few ZIP disks. I did think about pouring boiling water over them but maybe I’ll run an electric drill straight through the pile. The ZIP disks were expensive and could still be useful to someone (100M capacity - is that useful? Maybe for a pre USB laptop?) but I don’t even have a drive to format them on so they will have to die.

I did once ask a friend who worked at the MOD if they used the official erase & re-write at least three times with random data method and what they actually used to sanitize old disks,

“A steam hammer” was the laconic reply.

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Putting a Stop to Hanging with Safe Copying

By Dave F in Reader

Posted in Coding, Security on May 15, 2009 at 2:36 pm

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Irritating isn’t it, when a program mysteriously sits there like a sulking teenager, refusing to even acknowledge your presence however hard you click, type or shout?

I’ve just written one of those apparently. In the interests of world peace and understanding I’ll explain how it can happen - “understanding is the first thing, it means so much to me” as Van Morrison might say.

In my experience the most common programming bugs are to do with buffer over runs and threads. Threading issues are a bit more recent and a bit more tricky to handle. Two (or more) threads execute (virtually or literally) simultaneously which can cause more chaos than I want to think about here but imagine one thread has locked data the other needs and won’t let go until has another piece of data, thread two has that locked and won’t go until it gets the first piece - deadlock (and a hang).

Buffer over runs are old and common bugs in coding. They most often cause crashes but can be utilities by malignant (or I suppose, benign) hackers so we are now encouraged to use “safe” routines that check the size of a receive buffer when copying data. You may think “That’s clever, how do they do that?” In the main they aren’t clever, they just check what you tell them to check so they can still be wrong, the good thing is they tend to error during development so are fixed.

strcpy(newbuf, oldbuf);

works fine until oldbuf happens to be bigger than newbuf which may not happen until some user does something the programmer never thought of.

strcpy_s(newbuf, newbuf_size, oldbuf);

will go wrong immediately if newbuf_size if wrong & will just truncate the copy if oldbuf is bigger. Job done.

How can over runs be used by hackers? If you over run newbuf and newbuf is a created on the stack (ie local variable which most things are) then you can write over the stack including the return address making the program return to the address you want not where it came from. If you are clever enough to get it to return to a data area and you have loaded the data area with code the program is suddenly executing your code. Of course you don’t need to be clever enough to write that kind of thing, just clever enough to use a hackers toolkit that does it for you.

Normally then over runs cause crashes by writing data over other data which confuses the program or writing a random return address so the program starts executing gibberish.

So how did I write a hanging program?

sub (int *from){

int to[10];

int i;

for (i=0; from[i]; i++)

to[i] = from[i];

etc…

}

In this case when the buffer over runs it writes into int “i” so if “from” contains 11 values of 5 i goes

0,1,2,3,4,5,6,78,9 5 (contents of from[10]), 6,7,8,9, 5, 6,7,8,9, 5,…..

and so on until someone puts it out of its misery.

If “from[10]” contains > 10 then the loop may end after it has written data to all sorts of random places. That’s why I’m usually better than to write such naff code. My fix has was…

#define MAX_FROM_LEN 10

sub (int *from){

int to[MAX_FROM_LEN];

int i;

for (i=0; i<MAX_FROM_LEN && from[i]; i++)

to[i] = from[i];

etc…

}

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Nah, Don’t Hang on to your PS2 Keyboards!

By Dave F in Reader

Posted in thin clients, Blogs on May 11, 2009 at 3:54 pm

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I might have been wrong in http://www.itpro.co.uk/blogs/davef/2009/05/08/hang-on-to-your-ps2-keyboards/

It looks like if you hold the shift key during the logoff, switch user procedure then you still get the login options so maybe you don’t need a PS2 keyboard at all - which makes more sense!

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Hang on to your PS2 Keyboards

By Dave F in Reader

Posted in thin clients, Security, Microsoft on May 8, 2009 at 3:26 pm

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No not play stations, the old PC keyboards with din plugs (PS2 connectors). I’ve just had all kinds of fun with a thin client running WES (windows embedded standard) which is a sort of XPe (XP embedded). The unit is locked down tighter than (insert your own analogy, mine might be to vulgar) so doing anything much with it is tricky. I mean, you can’t even see drive C - ”My Computer” consists of RAM Drive Z.

That is if you are a user, as an Administrator you can access drive C, and can type commands to “run” from the Start button - ma-ha-ha tomorrow the world etc etc.

So how do you get to be an administrator? The same as any windows system, log in as administrator with Administrator as the password obviously.

But it never shows a login prompt - to get a login prompt you must hold down the shift key as windows loads. After some hours, days weeks, … OK a couple of goes, it occurred to me it seemed to load all the USB devices AFTER windows had booted and this was a USB keyboard (as supplied with the unit). I plug in my old PS2 keyboard and I’m in - tomorrow the world etc.

Once I could see drive C I could copy stuff onto it off a USB key, did I forget to click the little green padlock and “commit” my changes to the flash drive? Of course not (well only the once and that doesn’t really count does it?).

So there we are - one WES Thin Client neatly configured. Pretty soon you’ll be able to spot the administrators, they’ll be the ones walking round with an old keyboard under their arm - and muttering “don’t forget the commit, don’t forget the commit, ….”

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Web Mail - Orange Cookies?

By Dave F in Reader

Posted in the web, Blogs, Security, Microsoft on May 5, 2009 at 1:01 pm

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I have a an old freeserve email account which is useful as I can pop3 to it and also access it via webmail. It is of course Orange web mail these days & it has only been since it has been Orange that I have intermittent problems logging in. This occurs sometimes with pop3 but mainly with web mail.

I have discovered the cause of the most recent problems, I don’t have “enable all cookies” set in my privacy settings (http://support.microsoft.com/kb/299331). Now I have done this I can access the web mail & delete some of the 1800 spams filtered off for me. Unfortunately as I have not received some mail I was expecting I will have to trawl through at least some of them