show flash and Secure Device Manager visible files

[zillah2004]

CCSP Self-Study Securing Cisco IOS Network (SECUR) Cisco Press,book says:

The files that will be visible from the show flash command are :"show flash"

1- sdm.tar,

2- sdm.shtml

3- sdmconfig.cfg

What does he mean by : "visible", is it meant to be: there are hidden files, that we can not see them by using "show flash" command ?

[carenas123]

To my knowledge, there is no hidden files for SDM. They might be tried to say these files are visible to us in the show flash command.

[zillah2004]

This is what I believed as well, but I was not sure