Since you know that it is art on the computer, it is just basically that. You use a program (like paint, or something more advanced) to create a picture, or bring a sketch to life. You can also create art and animation through more complex things such as coding and stuff, but those are some basics.
Hope this helps you!
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The five eras are general- purpose mainframe and minicomputer computing, personal computers, client/server networks, ...
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"It is media that is distributed in paper form, such as magazines and newspapers."