Martin, Chuck
Sorry about that. It was the "cron" field in the "moodle_blocks" database table that confused me. I see now that the value in the cells of that field are all zero - probably meaning they don't use the cron 
.
Sorry to disagree with the Master Moodler but, six months ago, in my foolishness, I ran a Moodle installation for about 6 weeks for two or three classes, without any cron at all. It functioned satisfactorily, as a place to distribute materials, for forums (without email notification of course, and suddenly a deluge at the end), and quizes (I think). The chron was there at the beginning of term for the student to enrol (confirmation emails) but part way through I changed servers or something and forgot to set up a chron again. Part the way through the term I realised that I was having to manually confirm the course enrollment of latecoming students (Art explains how here) who were not getting enrollment confirmation mails and eventually twigged.
Of course one gets nothing like the full functionality, I wasn't (don't) use most on the functions that Martin mentions, so if you don't have a cron and cannot afford one (or don't want to change ISP), it might be worth a try.
But perhaps cron-essential-functionality was brought in since July last year.
Tim
tkmt