computer science

IBM 740

IBM 740 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 740 rather than just read about it. In short: The IBM 740 CRT Recorder was announced in 1954 and used with the IBM 701, IBM 704, and IBM 709 computers to draw vector graphics images, point by point, on 35 mm photographic film (i.e. microfilm). The 740 film recorder contained digital-to-analog converters and a 7-inch, high precision, electrostatic CRT.

Key takeaways

IBM 740 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 740 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IBM 740 from memory before moving on to harder problems.

Reference excerpt

The IBM 740 CRT Recorder was announced in 1954 and used with the IBM 701, IBM 704, and IBM 709 computers to draw vector graphics images, point by point, on 35 mm photographic film (i.e. microfilm). The 740 film recorder contained digital-to-analog converters and a 7-inch, high precision, electrostatic CRT. The raster size was 1,024 by 1,024, but only 256 resolved spots could be displayed on a vertical or horizontal line. Points could be displayed in one of two intensities, and a line could be drawn from a point, vertically or horizontally, to the edge of the display to form an axis. Each point to be displayed was stored in a single 36-bit word, with 10 bits each for the X and Y coordinates, and 3 control bits, one to set either high or low intensity and two to indicate that an X or Y axis is to be drawn starting from the given point. If both the X and Y axis bits were set, a 45-degree line was drawn. The 740's CRT used a short persistence P11 phosphor. The film used was 35 mm and was stored in a magazine that could hold up to 100 feet. ASA 200 speed film was recommended. The film could be advanced under computer control. The IBM 780 CRT Display was a monitor that could be attached to the 740 and mirror to an operator what was being drawn on 740's CRT. The 780 had a 21-inch CRT with a longer persistence (2 second, nominal) P7 phosphor.

See also IBM 2250 Phosphor#Standard phosphor types

References IBM 709 Data Processing System, Form A22-6501-0, 1958, p. 106ff. IBM 740 Cathode ray tube output recorder at the Wayback Machine (archived 2011-08-05) Stephen H. Kaisler (2018). First Generation Mainframes-The IBM 700 Series (PDF). Cambridge Scholars.

External links [1]

Illustrations

Worked examples

Example 1 — a first encounter with IBM 740

Start with the simplest possible case. Write down what IBM 740 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 740 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 740 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 740

In research: IBM 740 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 740 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 740 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 1954, Computer graphics stubs, History of human–computer interaction, so understanding it makes those chapters shorter.
In everyday life: Look for IBM 740 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 740 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IBM 740 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 740 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IBM 740 in simple terms?

Why does IBM 740 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 740?

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 740.