It was listed in Add/Remove, so I installed it (8.10, which had
been updated from 8.04, and from 7.10 before that). This is the
related blurb:

"system-cleaner-gtk finds and removes cruft from a system.
Cruft is (currently) packages that apt marks as automatically
removable, or that Ubuntu no longer supports.

"Homepage: https://wiki.ubuntu.com/CleanupCruft"

-------------

When installation was finished there was a message to
double-click the icon of a program I wish to run.
Having installed programs but not having been able to
find them without going to a Forum and have someone
who happened to know the previous name of the program
suggest I try running that, I double clicked. Nothing.

OK, run "locate system-cleaner-gtk" and bingo. A file
with that name is here:

/usr/share/app-install/desktop/system-cleaner-gtk.desktop

along with nine hundred thousand other files, one
for every existing program my repositories make
available. Then ls -l to learn it is not executable.

1) What are those files in /usr/share/app-install/desktop?

2) Anyone know how to find if this program was actually
installed and if so how to run it? FWIW "locate cleaner"
turns up nothing else with the word "system" -- only
that enigmatic file among enigmatic files.

I'm beginning to think there may be things about Linux
that I won't find out by pressing the F1 key. Are there
some sort of tablets I could take after each meal to
soften the learning curve?