computer science

Open Computer Network

Open Computer Network 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 Open Computer Network rather than just read about it. In short: OCN (オーシーエヌ), or Open Computer Network(オープン・コンピュータ・ネットワーク:Ōpun Konpyūta nettowāku), is the largest Japanese Internet service provider, with over 7 million subscribers. It is owned by NTT Communications Corp, one of the largest telecommunication companies in the world.

Key takeaways

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

Reference excerpt

OCN (オーシーエヌ), or Open Computer Network(オープン・コンピュータ・ネットワーク:Ōpun Konpyūta nettowāku), is the largest Japanese Internet service provider, with over 7 million subscribers. It is owned by NTT Communications Corp, one of the largest telecommunication companies in the world. It offers dial-up and ISDN, DSL up to 50 Mb/s and fiber up to 200 Mbit/s download and 100 Mb/s upload. As a result of regulations intended to promote competition, OCN themselves offer only internet service (routing); the physical line can be offered by NTT (the parent corporation), or by another company. Speeds up to 1 Gb/s are offered in Western Japan, while in East Japan only 200 Mb/s is officially offered for residential use, even though the underlying fiber infrastructure is capable of 1 Gb/s. OCN also offers an MVNO mobile broadband service called "OCN Mobile One", based on NTT Docomo's LTE infrastructure. Initially it started out as a data-only service, but more recently OCN Mobile One also offers an onseikake SIM card (音声対応SIMカード) that provides full service (data, SMS and voice) without requiring any calling app.

Worked examples

Example 1 — a first encounter with Open Computer Network

Start with the simplest possible case. Write down what Open Computer Network 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 Open Computer Network 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 Open Computer Network 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 Open Computer Network

In research: Open Computer Network 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 Open Computer Network 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: Open Computer Network is common in secondary-school and first-year university syllabi. It links to neighbouring topics Internet service providers of Japan, Japanese company stubs, NTT Communications, so understanding it makes those chapters shorter.
In everyday life: Look for Open Computer Network 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 Open Computer Network in 20 minutes

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

Frequently asked questions

What is Open Computer Network in simple terms?

Why does Open Computer Network 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 Open Computer Network?

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 Open Computer Network.