Volatile, Nonvolatile or Read-Only

About this interactive

Storage is described by what happens to the data, and this lesson gives three characteristics to tell apart. Volatile storage keeps data only while it has power. RAM and the CPU's cache are volatile: they hold what the computer is working on right now, very fast, and empty the moment the machine shuts down. That is a feature, not a flaw. Each start is a clean slate, and nothing from the last session lingers in memory. Nonvolatile storage keeps data with the power off, and you can write to it again and again. Solid state drives, hard drives, USB flash drives, SD cards, floppy disks and backup tape are all nonvolatile: save something today and it is still there tomorrow, and you can overwrite it next week. Read-only storage keeps data with the power off too, but it cannot be changed. A pressed CD-ROM, a shop-bought DVD or music CD, and a chip programmed at the factory are read-only: the data was set once and is only ever read. A punch card counts as well, since you cannot un-punch a hole. Read-only media are nonvolatile as well, so ask two questions in order. First: does the data survive power-off? If not, it is volatile. Second: can it be rewritten? If it can, it is nonvolatile; if it is fixed for good, it is read-only. Solid state is the tricky medium, because it turns up in all three bins: RAM chips are volatile, an SSD is nonvolatile, and a factory-programmed ROM chip is read-only. The medium does not decide the characteristic; what the storage is for does.

What you'll learn

Decide whether a storage need or device calls for volatile, nonvolatile or read-only storage from whether the data must survive power-off and whether it must ever change
Recognise RAM and CPU cache as volatile, drives and cards you save to as nonvolatile, and pressed discs and factory-programmed chips as read-only

Aligned to

CompTIA Tech+

1.3 Illustrate the basics of computing and processing.

2.3 Explain the purpose of common internal computing components.

2.5 Compare and contrast storage types.

Key terms

Volatile Memory: A category of storage that requires continuous electrical power to retain its contents; when power is removed, all data is lost. RAM is the primary example, used to hold the programs and data a CPU is actively working with.
Non-Volatile Memory: A category of storage that retains data even when power is removed, used for persistent storage of the operating system, applications, and user data; SSDs and ROM are examples.
Read-only Memory: Non-volatile memory whose contents are set at manufacture and cannot be modified during normal operation. Stores firmware and boot instructions that persist without power.
Random Access Memory: Volatile memory that temporarily stores data and program instructions the CPU is actively using, allowing fast read and write access from any memory location. RAM contents are lost when power is removed, unlike persistent storage.
CPU Cache: A small, fast memory built into the CPU chip that temporarily holds data immediately before and after processing.
Solid State Drive: A storage device that uses flash memory chips with no moving mechanical parts to store data persistently, offering faster read/write speeds, lower latency, and greater durability than traditional hard disk drives. SSDs connect via SATA, NVMe, or M.2 interfaces.

Topics

Volatile Memory Non Volatile Memory Read Only Memory Interactive Streak Sort

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