Completes the file processing.
Computer terms often come from business. Early computer files imitated the paper files of the time. Closing a file means gathering up everything that should go into it and filing it away.
The close() method should always be used when a program is done with a file. If a file is not closed, the program might end before the operating system has finished writing data to the file. The data written to the file might be lost!
Or it might not. Depends on how busy the operating system is. This is a notorious computer bug! It can be very frustrating, because sometimes a buggy program will work correctly, and sometimes not.