I don't know of a solid source, but I've heard anecdotally that computer programming and operation roles in major corporations of the '60s and '70s tended to be dominated by women, partly because the kinds of tabulation and collation that big business wanted were extensions of existing secretarial work, but also for the more immediate practical reason that the average female office worker of the time was far more likely than her male colleagues to already be an experienced typist.