Commodore PET 2001-8's have the built-in cassette player, but many of the internal players no longer work. Here is how to use an external cassette player from a VIC-20 or newer PET:
1. Plug external cassette unit into the port on the far left (facing from the back). The port has slot guides that should match your cassette jack.
2. The 2nd cassette port is assigned the number "2", so the command to access the 2nd cassette drive is
..where FILENAME = the file you wish to open. If you have a cassette but you don't know what the name of the program is, you can get a directory by substituting the FILENAME with the * character. Get a pen and write down the file names as the system lists them to your screen. Even a short program will take 30 seconds or more to load be patient.
Note that the oldest PET's do not have the ability to interface with disk drives unless the ROMS are updated.