The file DEMOSHOW.TXT on Disk #3 is a CADD batch file. Batch files are mentioned on page 10 of the Sneak Preview manual. 

To run DEMOSHOW as a CADD batch file, follow the instructions below.

IF YOU USE A HARD DRIVE: 

Make sure DEMOSHOW.TXT is loaded in the same directory as all other Sneak Preview files. Start up CADD Sneak Preview as usual, and load a drawing. At the prompt at the bottom of the CADD screen, type LB  then type DEMOSHOW and press [ENTER]. 

IF YOU USE TWO FLOPPY DRIVES:

Start CADD Sneak Preview with Disk #1 in Drive A: and Disk #3 in Drive B:. Load any drawing. At the prompt at the bottom of the CADD screen, type  LB  then type DEMOSHOW and press [ENTER].