computer science

IBM 2790

IBM 2790 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 IBM 2790 rather than just read about it. In short: The IBM 2790 Data Communications System is a family of devices intended for "in-plant data communications and production monitoring." It is described as a two-way data communications system designed to accommodate large volumes of short messages from many in-plant locations or from smaller groups of terminals at remote locations. The 2790 consists of one IBM 2715 Transmission Control Unit, or an IBM 1800 Data Acquis…

Key takeaways

IBM 2790 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 IBM 2790 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IBM 2790 from memory before moving on to harder problems.

Reference excerpt

The IBM 2790 Data Communications System is a family of devices intended for "in-plant data communications and production monitoring." It is described as a two-way data communications system designed to accommodate large volumes of short messages from many in-plant locations or from smaller groups of terminals at remote locations. The 2790 consists of one IBM 2715 Transmission Control Unit, or an IBM 1800 Data Acquisition and Control System, which controls the other system components. The 2715 supports up to 32 KB of magnetic core memory with a 1.2 μs cycle time, an internal disk for microcode load, a 2740 printer/keyboard, and a real time clock. The 2715 provides terminal control, transaction assembly, data-entry checking, message routing, transaction storage, and transfer of data to and from a IBM System/370, IBM 1800, or an IBM System/7.

2715 Model 1: Used for local operation 2715 Model 2: Used for remote attachment with a binary synchronous communication adapter such as a 270x communications controller. The 2715 supports a mix of other devices, all connected by a two-wire loop operating at 500 kbit/s. There are numerous data entry devices that can be attached:

The IBM 2791 Area Station is a tabletop unit attached to the 2790 loop. The 2791 can read ten column identification badges and eighty column punched cards, and has a twelve key pad for direct entry of numeric data. The 2791 can attach up to thirty-two 2795/2796 data entry units, a 1053 printer, up to three 1035 remote badge readers, and an OEM device. The 2791 has nine user defined "transaction buttons". Up to 100 2791/2793 can be attached. The IBM 2793 Area Station is similar, but lacks the ability to accept input data directly. It can attach up to thirty-two data entry units and a 1053 printer. Up to 100 2791/2793 can be attached. The IBM 2795, 2796 and 2797 Data Entry Units are compact industrial units for reporting job and machine status and production information. Both have two ten-position switches and a ten column badge reader. The 2796 has an additional two switches and allows for manual entry of up to four digits. 2740 Communications Terminal (one) 2798 Guided Display Units. This is a versatile and compact data entry and output unit with a 56 character keyboard, 8 control keys and 16 position visual display. Up to 12 can be attached.

References

Worked examples

Example 1 — a first encounter with IBM 2790

Start with the simplest possible case. Write down what IBM 2790 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 IBM 2790 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 IBM 2790 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 IBM 2790

In research: IBM 2790 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 IBM 2790 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: IBM 2790 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, IBM computer terminals, Industrial automation, so understanding it makes those chapters shorter.
In everyday life: Look for IBM 2790 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 IBM 2790 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IBM 2790 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 IBM 2790 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IBM 2790 in simple terms?

Why does IBM 2790 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 IBM 2790?

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 IBM 2790.