Ask HN: Why do ATMs run on Windows?

Well, if your bank's internal systems/offices already run Windows, then it is better to use the same platforms for your ATMs too - you can reuse code between the two systems, and you only need one developer team instead of two.

Also, ATM development started way before Linux was a major player and people basically only had MS-DOS or OS/2 as choices - and as banking software develops at the same speed as a glacier moves (and those ATMs tend to grow OLD), you're stuck in a lock-in effect.

For the same reason everyone writes other financial systems for Windows. It's a popular platform with rich frameworks and a large developer base.

The current versions (>= Windows 7) of Windows are pretty secure. Even the last patched up version of XP isn't awful. That said, my experience with ATMs has been that nobody does a good job of hardening ATMs.

Why wouldn't they run windows? I don't get all this drama with ATM's and XP. They are (should be) physically secure, meaning no usb ports available, cd-rom, no public network. THey are completely locked down. Many of them are still running windows95 and they seem to work pretty well.

What would you recommend then? Mac? Linux?

Atm's, from what I know, are generally not connected to wifi. Most are directly wired to either DSL or to a modem making it the end users issue(aka the person who owns the property which the ATM is on).