cmd.exe tab completion character set to something odd

Question

Background:

I have an install of Windows XP SP3 OEM that I use often. Recently its cmd.exe somehow forgot that pressing TAB means I want to use the completion feature.

I found out how to fix this problem here, and it worked just fine.

Cause for concern:

I was surprised and confused by what the completion character was set to.

The completion character was set to the ASCII SUB character, 0x1a, or 26.

My questions:

1. What is the ASCII SUB character, 0x1a, or 26, used for? Can I type it? Can I type it in one keystroke?
2. What could have caused it to be set to anything else that the ASCII TAB character, 0x09, or 9?

Answer 1

In the context of the Windows command prompt, ASCII 26 represents an end of file character. You can type it in the command prompt by holding and releasing Alt + 2 + 6 (in that order) or Ctrl + z. It will produce ^Z (Control-Z). In other applications, you will see a right-facing arrow with the Alt combination, and the Ctrl combination likely performs an undo operation, depending on the software.

I haven't personally seen this behavior, maybe some software you installed had altered it. A very interesting problem though nonetheless!