computer science

HIL bus

HIL bus 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 HIL bus rather than just read about it. In short: The HP-HIL (Hewlett-Packard Human Interface Link) is the name of a computer bus used by Hewlett-Packard to connect keyboards, mice, trackballs, digitizers, tablets, barcode readers, rotary knobs, touchscreens, and other human interface peripherals to their HP 9000 workstations. The bus was in use until the mid-1990s, when HP substituted PS/2 technology for HIL.

Key takeaways

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

Reference excerpt

The HP-HIL (Hewlett-Packard Human Interface Link) is the name of a computer bus used by Hewlett-Packard to connect keyboards, mice, trackballs, digitizers, tablets, barcode readers, rotary knobs, touchscreens, and other human interface peripherals to their HP 9000 workstations. The bus was in use until the mid-1990s, when HP substituted PS/2 technology for HIL. The PS/2 peripherals were themselves replaced with USB-connected models. The HIL bus is a daisy-chain of up to 7 devices, running at a raw clock speed of 8 MHz. Each HIL device typically has an output connector, and an input connector to which the next device in the chain plugs; the exception is the mouse which has only the output connector. HIL buses can be found on HP PA-RISC and m68k based machines, some early HP Vectra computers, as well as in some HP/Agilent Logic Analyzers. HP-UX, OpenBSD, Linux and NetBSD include drivers for the HIL bus and HIL devices. The HP-HIL bus uses specific 4-pin, 6-pin, or 8-pin SDL connectors, somewhat similar to the 8P8C 8-pin modular connector commonly (though incorrectly) called the RJ-45. The bus can reportedly also use a 9-pin D-subminiature DE-9 connector. A HIL to PS/2 converter is available, namely the HP A4220-62001.

Specification HP-HIL Technical Reference Manual, HP P/N 45918A

External links

Illustrations

Worked examples

Example 1 — a first encounter with HIL bus

Start with the simplest possible case. Write down what HIL bus 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 HIL bus 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 HIL bus 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 HIL bus

In research: HIL bus 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 HIL bus 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: HIL bus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, Hewlett-Packard products, Human–computer interaction, so understanding it makes those chapters shorter.
In everyday life: Look for HIL bus 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 HIL bus in 20 minutes

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

Frequently asked questions

What is HIL bus in simple terms?

Why does HIL bus 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 HIL bus?

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 HIL bus.