Of software, used to emphasize that a program is unaware of some important fact about its environment, either because it has been fooled into believing a lie, or because it doesn't care. The sense of ‘happy’ here is not that of elation, but rather that of blissful ignorance. “The program continues to run, happily unaware that its output is going to /dev/null.” Also used to suggest that a program or device would really rather be doing something destructive, and is being given an opportunity to do so. “If you enter an O here instead of a zero, the program will happily erase all your data.” Nevertheless, use of this term implies a basically benign attitude towards the program: It didn't mean any harm, it was just eager to do its job. We'd like to be angry at it but we shouldn't, we should try to understand it instead. The adjective “cheerfully” is often used in exactly the same way.