8 Files: Electronic Storage

So far, the programs in this book have performed calculations and printed results. That’s a good start, but it only takes you so far in the real world.

Most practical applications (reservation systems, database systems, spreadsheets, and even games) store and retrieve persistent information. This is data that hangs around after the program ends, and even after the computer is turned off.

In contrast, main memory (“RAM”) is certainly a kind of storage, but it’s not persistent. As soon as the computer loses power, all the data in memory is lost forever (which is why you kick yourself if you don’t save to disk in Word often enough). But even if main memory were more permanent—even if it didn’t zero out when the computer ...

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