Almost everyone knows their five digit ZIP code, and probably a few others within their city, but what’s up with the extra four digits you sometimes see on mail? Let’s start with those first five ...

Got a problem with an Excel spreadsheet. I have a non-specific data column in an Excel 2007 spreadsheet. The data in one column is zip codes in the form of both zip (5 digit, 00000) and zip+4 (10 ...