Oh, Excel, how I hate to love you... As is the case for many, Excel is one of my main tools. From financials to data gathering to electrical, mechanical or so

Oh, Excel, how I hate to love you... As is the case for many, Excel is one of my main tools. From financials to data gathering to electrical, mechanical or software engineering, Excel has always been there. It is fair to say I have made lots of money thanks to this tool. And yet, every so often... Many years ago a rounding error in a complex Excel tool we wrote to calculate coefficients for an FPGA-based polyphase FIR filter cost us a little over six months of debug time. I still remember the "eureka!" moment at two in the morning --while looking at the same data for the hundredth time in complete frustration-- when I realized we should have used "ROUNDUP()" rather than "ROUND()". Most recently, I was working with a client who chose to build a massive Excel sheet to gather a bunch of relevant data. The person doing the work seems to think they know what they are doing (conditional formatting and filtering don't make you an expert). This poor spreadsheet has every color in the rainbow and a mess of formulas. It's impossible for anyone but the guy who created it to touch it. Here's a hint: Do not mix data with presentation. Where have we heard that before? This is one of my pet peeves with Excel. If you need to gather a bunch of data, do it. Treat Excel like a database (apply normalization if you can!) and keep it with as little formatting as you possibly can. Then do all the formatting and calculations on a "Presentation" sheet or sheets. Just don't pollute your database with formatting. EDIT: Thinking about the UK problem, if they were working with a ".xlsx" file and accidentally saved it in ".xls" form, well, as they say, "There's a warning dialog for that". What surprises me the most about these kinds of incidents is that people keep working on the same single document. In other words, no semblance at all of what the software business knows as version control. Decades ago I adopted the idea that storage is cheap and always getting cheaper. If I am working on something critical, I never work more than one day without a backup. I make a copy and continue editing. In most cases I make a new copy every single day.