Bag of Beans

Joel on Software examines the recent Excel 2007 bug.

By now you’ve probably seen a lot of the brouhaha over a bug in the newest version of Excel, 2007. Basically, multiplying 77.1*850, which should give you 65,535, was actually displaying 100,000.

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xkcd presents a tough logic puzzle.

I’ve done my best to make the wording as precise and unambiguious as possible (after working through the explanation with many people), but if you’re confused about anything, please let me know. A word of warning: The answer is not simple. This is an exercise in serious logic, not a lateral thinking riddle. There is not a quick-and-easy answer, and really understanding it takes some effort.

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Related:

• Classic Computer Science Puzzles
• William Wu’s Riddles
• Newcomb’s Paradox
• 13 Balls problem: One of the hardest interview questions
• World’s hardest Sudoku puzzle

If you’ve ever wondered why most staplers have the feature to bend staples outwards as well as inwards, here’s your answer.

And now for what may be the most prosaic post in Eternal Recurrence history: examining your stapler! Yes, your stapler. A simple object you’ve used thousands of times and probably feel like you’ve mastered. Well, think again. Your stapler may possess a mysterious feature…

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Coding Horror has a nice summary of classic puzzles in computer science, which you may have seen in your university courses.

I prefer to think of programming languages as utilitarian tools for real world problems. They let me accomplish pragmatic (and often prosaic) goals. PHP is about as unsexy a language as you’ll ever find, but does that matter when it’s the technology driving the current Boardwalk and Park Place of the web world? I’m not a fan of puzzle questions in interviews; I’d rather have potential developers give me a presentation or write a reasonably useful program in the real development environment they’ll be using on the job. Solve all the puzzles you want, but the only one we’re getting paid to solve is the customer’s problem.

That said, many fundamental computer science concepts can be summarized well in puzzle form, which aids tremendously in teaching and learning these key concepts. Here’s a quick list of the classic computer science puzzles that I remember from my university days

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You can now rest easy, knowing that, indeed, you can install 145 operating systems on one PC.

An operating system needs to reside in a home. That is a partition to me. I used 2×300Gb Pata disk and 2×200 Sata Disk to set up 152 partitions. I always put one operating system in one partition. As an extended partition of each hard disk has no storage of its own, one data-only partition is needed for my personal data, another data-only partition to house the common boot loader and one Swap partition is needed for all the Linux I ended up losing 7 partitions leaving 145 partitions to house the 145 operating systems.

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Coding Horror has written an informative article on Rainbow Tables, and why Windows servers can be particularly vulnerable.

The multi-platform password cracker Ophcrack is incredibly fast. How fast? It can crack the password “Fgpyyih804423″ in 160 seconds. Most people would consider that password fairly secure. The Microsoft password strength checker rates it “strong”. The Geekwisdom password strength meter rates it “mediocre”.

Why is Ophcrack so fast? Because it uses Rainbow Tables. No, not the kind of rainbows I have as my desktop background.

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This instructable shows an alternative to etching PCBs with Ferric Chloride.

Ferric chloride is kinda nasty stuff. Quick to exhaust its etching power, non-reusable, kinda pricey, and ends up full of copper salts that are bad for the environment if you’re pouring them down the drain. (For instance: How to Dispose of Ferric Chloride in this FAQ. )

Wouldn’t it be nice if there were an etchant that you could re-use indefinitely so that you don’t have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it’s prettier too.)

I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)

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