It used to be, many years ago, that when you bought a computer, it was much more expensive than it is now, and one reason is because it came fully loaded with software. For the PC, it was Microsoft Word, Excel and, I think, Power Point. Now, if you wnat that type of software, you have to buy it. (Every computer comes with a text program, which allows you to type things, but it is like kindergarten typing compared to what you can do with a word processing program like Word or Word Perfect.
If you don't want to spend money on those programs, you can download Open Office. (OpenOffice.org). It gives you a word processor, a spreadsheet program (so you can do your budget or keep your books), a paint program so that you can do illustrations, and so on. It's totally free, but it would be nice if you'd make a donation (via PayPal or credit card - I'll explain what these are later) of $10 or so or more, just to thank them for their hard work!
The Open Office word processor is relatively sophisticated, but if you intend to publish books or write research papers, I myself prefer Microsoft Word. Word Perfect has never been my favorite program, although I can use it...
But if you are trying to kit out your computer as inexpensively as possible, Open Office is the way to go.