The basic function of computer memory is essentially to store data. Depending on the type of data it stores and the role it plays in computer operation, however, memory performs several different functions. Although all of these functions involve data storage, RAM, ROM, flash memory and hard drives each perform a different and necessary function to keep a computer and its peripherals working.
Random access memory (RAM) provides temporary application data storage. Instead of having to go back and find information on the hard drive every time a computer needs a piece of data, the computer temporarily stores frequently used files on RAM, making them easier to find. When the computer shuts down, all the data in RAM is erased or transferred to the hard drive, making room for new data when the computer begins operating again.
A hard drive is core of a computer's data storage. It provides memory space for system and user files -- everything from your operating system to documents and images. In mechanical terms, a hard drive is a rotating disk treated with a magnetic coating, similar to the magnetic ribbons that store data on cassettes. A moving arm reads and copies data to and from the rotating disk, allowing you to open files from the hard disk or save new data.
Flash memory, the common term for electronically erasable programmable read-only memory (EEPROM), is used in computer video game cards and to store some vital system information. Unlike other memory types that copy or erase data byte-by-byte, EEPROM can edit data in groups of bytes, making it a popular choice for devices like memory sticks and cameras where the data stored is constantly changing. Unlike hard drives, EEPROM does not require a fragile moving arm, prompting some computer manufacturers to move toward replacing hard disks with flash architecture, although the technology remains more expensive than hard disks.
Read-only memory (ROM) is used to store data that controls the most basic computer functionality, such as starting up, detecting peripherals and operating the computer fan. As the name suggests, the data cannot be edited by the system or users and, unlike RAM, the data stays recorded even when the computer is off. Like hard drives and flash memory, ROM is an example of non-volatile memory -- meaning that it remains in place when the power is off -- while RAM is considered volatile memory.
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