I remember AIX doing that when you entered an upper-case login. Probably still does. https://www.ibm.com/docs/en/aix/7.1?topic=s-stty-command#stty__row-d3e5773

I remember AIX doing that when you entered an upper-case login. Probably still does. https://www.ibm.com/docs/en/aix/7.1?topic=s-stty-command#stty__row-d3e57730 https://www.ibm.com/docs/en/aix/7.1?topic=s-stty-command#stt... xcase Echoes uppercase characters on input, and displays uppercase characters on output with a preceding \ (backslash). iuclc Maps uppercase alphabetic characters to lowercase. olcuc Maps lowercase alphabetic characters to uppercase on output. Solaris (Illumos) source code is consistent with this. So for an upper-case only keyboard, uppercase letters are lowercase. To type an uppercase letter, precede it with a \. The tty layer handles the conversion so programs don't know or care what you're actually typing -- they just read (and write) normal upper and lower case characters.