Except you don't have to be able to program to be accepted to a CS program, so that shouldn't have a dramatic effect on why there are so few female students interested in CS.
This is true, but I'd contend that people who already know how to program are a lot more likely to enter a CS program, so you still get an imbalance.
The situation I'm describing is based on my experience in the U.S. In other countries it might well be the case that hardly anybody male or female, learns to program before college. If my theory is correct, then there should be less of a gender imbalance in CS programs in those countries.
Data point for one non-U.S. country: in India, computer programming (in BASIC/Pascal/C/etc.) (and also a bit of elementary computer architecture and elementary computer science) has been part of the schools' curriculum for some years now, AFAIK. High schools, that is, not colleges. (The use of the term "school" to mean college (as well as high school or lower) is an Americanism, I believe.) Also, even in schools that don't have computer subjects as standard, many students join private computer classes. I'm not commenting on the quality of those classes, which can vary widely - from hole-in-the-wall fly-by-night operators (cashing in on the software "boom") to quite good ones, that's another story entirely ...
Also, I don't have specific numbers, but going by observation and reports, there are a good number of girls/women who go into the software field. It's seen as a good option for women workers here because it is a white-collar job, seen as prestigious - good office environments, at least in the mid- to high-end companies, air-conditioning, good pay compared to many other types of jobs, etc.)
But you have to know about what programming and computer science is about before WANTING to apply to a CS college. Or you can just rely on the media or your parents to tell you that CS pays good money - but that's just disastrous.
I think that CS does not appeal to females simply because females are more social than males; spending endless hours in front of a computer is not really that attractive.
