It all depends on the institution where you plan to do your masters. Some places may require that you either have a degree in a computer science related field, or some background (whether formally or informally) in computing. considering how flexible institutions are becoming, some may accept you if you work in the field of computing even though you have a BSc in a humanities based area. I would suggest you do some research into MSc programmes at different institutions to get an idea of what the criteria is for acceptance. I have a friend who did a BSc. in linguistics (humanities) and did a MSc. in HRM, so again, just boils down to where you apply to.
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