char *string_value = new char[32];

In computer science we're quite accustomed to using powers of 2 whenever a numerical limit is required. e.g. The string can be 32 characters long, the filename can be 64 characters, while the number of entries in the listbox can number 1024.

These uses seldom require powers of 2 (e.g. while it makes sense for an ASCII string to be multiples of 4 bytes if it's long aligned and you care about that, it could just as efficiently be 28 or 36 characters long), but nonetheless it's ingrained into most developers' minds.

I chuckled seeing the commercial for some overpriced timed-interval air freshener. It allows you to select 9, 18, or 36 minute intervals between sprays. While not exactly compliant (I'll bet that it was originally 8, 16 or 32 minutes, but they added some lag to the minute counter to avoid it seeming computeresque), and in this case I can understand why the microcontroller developer chose powers, the spirit of the power of 2 lives on.