computer science

Memory address register

Memory address register 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 Memory address register rather than just read about it. In short: In a computer, the memory address register (MAR) is the CPU register that either stores the memory address from which data will be fetched to the CPU registers, or the address to which data will be sent and stored via system bus. In other words, this register is used to access data and instructions from memory during the execution phase of instruction.

Key takeaways

Memory address register 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 Memory address register to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Memory address register from memory before moving on to harder problems.

Reference excerpt

In a computer, the memory address register (MAR) is the CPU register that either stores the memory address from which data will be fetched to the CPU registers, or the address to which data will be sent and stored via system bus. In other words, this register is used to access data and instructions from memory during the execution phase of instruction. MAR holds the memory location of data that needs to be accessed. When reading from memory, data addressed by MAR is fed into the MDR (memory data register) and then used by the CPU. When writing to memory, the CPU writes data from MDR to the memory location whose address is stored in MAR. MAR, which is found inside the CPU, goes either to the RAM (random-access memory) or cache. The MAR register is half of a minimal interface between a microprogram and computer storage; the other half is a MDR. In general, MAR is a parallel load register that contains the next memory address to be manipulated, for example the next address to be read or written.

References

Worked examples

Example 1 — a first encounter with Memory address register

Start with the simplest possible case. Write down what Memory address register 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 Memory address register 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 Memory address register 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 Memory address register

In research: Memory address register 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 Memory address register 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: Memory address register is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, Digital registers, so understanding it makes those chapters shorter.
In everyday life: Look for Memory address register 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 Memory address register in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Memory address register 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 Memory address register out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Memory address register in simple terms?

Why does Memory address register 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 Memory address register?

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 Memory address register.