computer science

IBM CPC

IBM CPC 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 CPC rather than just read about it. In short: The IBM Card-Programmed Electronic Calculator or CPC was announced by IBM in May 1949. Later that year an improved machine, the CPC-II, was also announced.

Key takeaways

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

Reference excerpt

The IBM Card-Programmed Electronic Calculator or CPC was announced by IBM in May 1949. Later that year an improved machine, the CPC-II, was also announced. IBM's electronic (vacuum tube) calculators could perform multiple calculations, including division. The card-programmed calculators used fields on punched cards not to specify the actual operations to be performed on data, but which "microprogram" hard-coded onto the plugboard of the IBM 604 or 605 calculator machine; a set of cards produced different results when used with different plugboards. The units could be configured to retain up to 10 instructions in memory and perform them in a loop. The original CPC Calculator has the following units interconnected by cables:

Electronic Calculating Punch IBM 604 with reader/punch unit IBM 521 Accounting Machine IBM 402 or IBM 417 The CPC-II Calculator has the following units interconnected by cables:

Electronic Calculating Punch IBM 605 with punch unit IBM 527 Accounting Machine IBM 407 or IBM 412 or IBM 418 Optional Auxiliary Storage Units (up to 3) IBM 941, each could store 16 decimal numbers with ten digits plus sign. From the IBM Archives:

The IBM Card-Programmed Electronic Calculator was announced in May 1949 as a versatile general purpose computer designed to perform any predetermined sequence of arithmetical operations coded on standard 80-column punched cards. It was also capable of selecting and following one of several sequences of instructions as a result of operations already performed, and it could store instructions for self-programmed operation. The Calculator consisted of a Type 605 Electronic Calculating Punch and a Type 412 or 418 Accounting Machine. A Type 941 Auxiliary Storage Unit was available as an optional feature. All units composing the Calculator were interconnected by flexible cables. If desired, the Type 412 or 418, with or without the Type 941, could be operated independently of the other machines. The Type 605 could be used as a Calculating Punch and the punch unit (Type 527) could be operated as an independent gang punch. Customer deliveries of the CPC began in late 1949, at which time more than 20 had been ordered by government agencies and laboratories and aircraft manufacturers. Nearly 700 CPC systems were delivered during the first-half of the 1950s.

See also Unit record equipment List of vacuum tube computers

References

IBM (October 1954). IBM Card-programmed Electronic Calculator; Model A1 using machine types 412-418, 605, 527, and 941 (PDF). 22-8686-3. Sheldon, John W.; Tatum, Liston (10–12 December 1951). "The IBM Card-Programmed Electronic Calculator". Joint AIEE-IRE Computer Conference. American Inst. of Electrical Engineers. pp. 30–36. Archived from the original on 28 June 2003. Barber, E.A. (1950). "Cam Design Calculations on the Card Programmed Electronic Calculator". Proceedings, Seminar on Scientific Computation November, 1949. IBM. pp. 52–57. 22-8296-0. Includes a 2-page listing Program Card Codings Cuthbert Hurd (1950). "The IBM Card-Programmed Electronic Calculator". Proceedings, Seminar on Scientific Computation November, 1949. IBM. pp. 37–41. 22-8296-0. IBM (1951). Proceedings, Computation Seminar August 1951. IBM. 22-8705-0. Many articles about the IBM CPC and 604.

External links IBM Archives: Card-Programmed Electronic Calculator (CPC) History of the IBM CPC at Stanford University Archived 2014-08-13 at the Wayback Machine "IBM Card Programmed Computer (CPC)" photograph at the Computer History Museum

Illustrations

Worked examples

Example 1 — a first encounter with IBM CPC

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

In research: IBM CPC 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 CPC 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 CPC is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1940s computers, Computer-related introductions in 1949, Computer hardware stubs, so understanding it makes those chapters shorter.
In everyday life: Look for IBM CPC 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 CPC in 20 minutes

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

Frequently asked questions

What is IBM CPC in simple terms?

The IBM Card-Programmed Electronic Calculator or CPC was announced by IBM in May 1949. Later that year an improved machine, the CPC-II, was also announced.

Why does IBM CPC 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 CPC?

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 CPC.