I downloaded the evaluation software from Keil, recently.
There were certain example programs in \Keil\C51\example programs.under this there is a project under the folder InfenionC517.
I am unable to understand what sort of a command we are expected to give in the line
gets (cmdbuf, sizeof (cmdbuf))
in the while loop of main-Sample517.c
Each example has an ABSTRACT.TXT describing it.
Did you read that file?