We go to fairly extreme lengths to try to maintain compatibility with older applications, as Raymond Chen's blog often demonstrates in vivid fashion. As an example of this, some of you may remember seeing Jim Allchin's demonstration of Visicalc (the earliest spreadsheet) at PDC 2003 running on Windows Vista (then known as "Longhorn", of course).
So I wondered - what is the oldest component still present in Windows Vista? After a bit of digging around, I think I've finally discovered the answer.
Dear old edlin, the very first line editor in MS-DOS, is still available for your batch editing pleasure over a quarter of a century after its introduction. According to wikipedia, edlin even pre-dates MS-DOS, having been written for an even earlier operating system that was one of the company's first acquisitions. My first exposure to MS-DOS was version 3.2 on my father's office computer, and I used to remember most of the mnemonic commands by heart. It's not a user-friendly tool, but it was fast to load and more forgiving of mistakes than the alternative of copy con filename.txt.
This is one secret that has mere curiosity value, but I still have a warm spot for this venerable editor and I salute its indefatigability!