To find out what version of Ksh you have installed on your machine:

Type this, followed by enter:

set -o vi

And then press these keys:

It will display something like:

Version M-11/16/88i                 ⇒ KSH-88
Version M-12/28/93                  ⇒ KSH-93
@(#)PD KSH v5.2.14 99/07/13.2       ⇒ PD-KSH

ksh --version

echo $KSH_VERSION