Typo3: variables, editable in backend

There is an easy way to define minor variables and make them editable in the typo3 backend. It can be done via extension settings. Just add in the constants.txt:

# cat=plugin.tx_extensionname//a; type=int+; label=How many loops should there be?
loopCount = 5
# cat=plugin.tx_extensionname//b; type=boolean; label= Do the cronjob?
doCronjob = 1

Whats important is the seemingly commented line above the variables, it is to define a type (here is a list of possible types) and a label.
In typo3 just click on “Template” on the left (while having selected the template page). In the dropdown on top select “constant editor” and then the tx_extensionname should appear in the dropdown below.
To make this available via $this->settings in the cronjob, add the following to the setup.txt:

plugin.tx_extensionname {
    settings {
        loopCount = {$plugin.tx_extensionname.settings.loopCount}
        doCronjob = {$plugin.tx_extensionname.settings.doCronjob}
    }
}
module.tx_extensionname < plugin.tx_extensionname