--- title: "Memory and Storage: RAM, ROM and the Backing Store" description: "Ordinary RAM holds working instructions and data and loses them without power. ROM retains firmware. Secondary storage keeps saved files between runs, but devices can fail. Compare capacity, access ti" canonical: https://lightmysky.com/learn/computing/memory-and-storage-ram-rom-and-the-backing-store-mt_AiXGJioO_S source: https://lightmysky.com/learn/computing/memory-and-storage-ram-rom-and-the-backing-store-mt_AiXGJioO_S.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Memory and Storage: RAM, ROM and the Backing Store Ordinary RAM holds working instructions and data and loses them without power. ROM retains firmware. Secondary storage keeps saved files between runs, but devices can fail. Compare capacity, access time, cost and physical risks for a stated use. Subject: Computing · Area: Computer Systems · Ages 15 to 16 Page: https://lightmysky.com/learn/computing/memory-and-storage-ram-rom-and-the-backing-store-mt_AiXGJioO_S ## Ready when they can - Distinguish what ordinary RAM, ROM and secondary storage retain without power - Explain why a typical desktop application loads needed instructions into RAM and saves lasting data to storage - Compare stated drive characteristics and calculate backup capacity under stated assumptions ## Lesson: RAM, ROM and saved files Ordinary RAM is volatile: it needs power to retain working instructions and data. ROM is nonvolatile memory used for firmware, the low-level instructions that help a device start. Some firmware memory can be updated through a special process. ROM is not the usual place to save changing documents. Restarting ends processes and starts the operating system again. It can release RAM held by unneeded processes or a program that keeps allocating unused memory. It does not fix every cause of slowness. Startup processes may return. Save work first; programs can write files during shutdown. A typical desktop application loads needed instructions and working data from storage into RAM. The CPU accesses them through the memory system, often using caches. This provides fast access during execution. Not every device works this way: some execute firmware directly from ROM. Working data belonging to a process is not a lasting save. Saving writes a version to persistent storage for later runs. If a change exists only in RAM, with no autosave or recovery copy, it is lost in a power failure. An older saved file can remain. Nonvolatile storage can still fail, so saving and backing up protect against different risks. HDDs use moving magnetic parts. SSDs use flash memory with no moving parts and usually have shorter access times. HDDs often cost less per gigabyte at high capacities, but compare actual models and prices. An SSD avoids some mechanical damage risks during a knock; either drive can fail. Choose using the stated capacity, cost, access time and physical risks. Keep a backup on separate storage and check that you can restore it. Space needed depends on file sizes, retained versions, compression and overhead. There is no universal twice-the-drive-size rule. For one uncompressed copy with no overhead, add all the file sizes: 250 GB plus 50 GB requires 300 GB free. *(drawing: Saving changes the main stored version. A backup adds a separate copy that you can test by restoring it.)* **Recap.** RAM is volatile; ROM and drives retain data without power. Save changes and keep a separate backup that you can restore. *Lesson, worked questions and flashcards about RAM, ROM and saved files were written for this dataset.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Inside the CPU: Fetch, Decode, Execute](https://lightmysky.com/learn/computing/inside-the-cpu-fetch-decode-execute-mt_YT-FSWnUKR) ## Optional connections - [Where a File Lives: Folders, Names and Backups](https://lightmysky.com/learn/computing/where-a-file-lives-folders-names-and-backups-mt_UvLO9CA3BY) ## Opens up - [The Memory Hierarchy and Why Caching Works](https://lightmysky.com/learn/computing/the-memory-hierarchy-and-why-caching-works-mt_0f5ArFPlxP) - [Packets and Protocols on a Network](https://lightmysky.com/learn/computing/packets-and-protocols-on-a-network-mt_IffXVDtfLX) - [Registers, Buses and the Fetch-Execute Cycle in Detail](https://lightmysky.com/learn/computing/registers-buses-and-the-fetch-execute-cycle-in-detail-mt_yjy3eSStzH)