computer science

Read–write memory

Read–write memory is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Read–write memory rather than just read about it. In short: Read–write memory, or RWM, is a type of computer memory that can be easily written to as well as read from using electrical signaling normally associated with running a software, and without any other physical processes. The related storage type RAM means something different; it refers to memory that can access any memory location in a constant amount of time.

Key takeaways

Read–write memory belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Read–write memory to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Read–write memory from memory before moving on to harder problems.

Reference excerpt

Read–write memory, or RWM, is a type of computer memory that can be easily written to as well as read from using electrical signaling normally associated with running a software, and without any other physical processes. The related storage type RAM means something different; it refers to memory that can access any memory location in a constant amount of time. The term might also refer to memory locations having both read and write permissions. In modern computer systems using memory segmentation, each segment has a length and set of permissions associated with it.

Types Read–write memory is composed of either volatile or non-volatile types of storage. Volatile memory is usually in the form of a microchip or other hardware that requires an external power source to enable data to persist. Non-volatile memory is considered static, or storage-type memory. This means that you can write data to it, and that information will persist even in the absence of a power source. Typically read-write speeds are limited to its bandwidth or have mechanical limitations of either rotation speeds and arm movement delays for storage types such as Cloud Storage, Hard Disk Drive or CD-RWs, DVD-RWs, SD cards, Solid-State Drive, SRAM, and DRAM, or other integrated circuitry.

History San Francisco in 1956, IBM was the first company to develop and sell the first commercial Hard Disk Drive (HDD). The drive was the Model 350 disk storage unit, which was 3.75 megabytes of data storage capacity and had fifty 24-inch diameter disks stacked on a spindle and sold to Zellerbach paper.

See also Read-mostly memory (RMM) Random-access memory (RAM)

References

Footnotes

Worked examples

Example 1 — a first encounter with Read–write memory

Start with the simplest possible case. Write down what Read–write memory claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Read–write memory before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Read–write memory ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Read–write memory

In research: Read–write memory appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Read–write memory in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Read–write memory is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, Computer memory, so understanding it makes those chapters shorter.
In everyday life: Look for Read–write memory outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Read–write memory in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Read–write memory means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Read–write memory out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Read–write memory in simple terms?

Why does Read–write memory matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Read–write memory?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Read–write memory.