Some bulletin boards charge a fee as does the utility company, so the modem isn't the only expense. Your county Extension agent has a modem in the office. C - Z. The first hard drive added to the machine is named C, the next D, and so on. Many systems now have one or more drives. The hard drive is permanent memory inside the equipment.
Any information stored on the hard drive remains there when the computer is turned off.
In order to have permanent records of computer output, you must have a printer. With the video display, the computer output is visible only as long as you keep it on the screen. With a printer, you can have a permanent printed copy of the computer output. Many types of printers exist, but the most common is the dot matrix printer. As with the other devices, keep it free of dust, the ribbon replaced when needed, and fed with paper.