computer science

Queued Telecommunications Access Method

Queued Telecommunications Access Method 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 Queued Telecommunications Access Method rather than just read about it. In short: Queued Telecommunications Access Method (QTAM) is an IBM System/360 communications access method incorporating built-in queuing. QTAM was an alternative to the lower level Basic Telecommunications Access Method (BTAM).

Key takeaways

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

Reference excerpt

Queued Telecommunications Access Method (QTAM) is an IBM System/360 communications access method incorporating built-in queuing. QTAM was an alternative to the lower level Basic Telecommunications Access Method (BTAM).

History QTAM was announced by IBM in 1965 as part of OS/360 and DOS/360 aimed at inquiry and data collection. As announced it also supported remote job entry (RJE) applications, called job processing, which was dropped by 1968. Originally QTAM supported the IBM 1030 Data Collection System, IBM 1050 Data Communications System, the IBM 1060 Data Communications System, the IBM 2671 Paper Tape Reader, AT&T 83B2 Selective Calling Stations, Western Union Plan 115A Outstations, and AT&T Teletype Model 33 or 35 Teletypewriters. By 1968 terminal support had expanded to include the IBM 2260 display complex, and the IBM 2740 communications terminal. QTAM devices were attached to a System/360 multiplexor channel through an IBM 2701 Data Adapter or IBM 2702 Transmission Control. By 1968 support for the IBM 2703 Transmission Control Unit had been added. QTAM was succeeded by TCAM which provided roughly similar facilities, but was not supported under DOS.

Structure QTAM consists of a Message Control Program (MCP) and zero or more Message Processing Programs (MPP). The MCP handles communications with the terminals, identifies input messages and starts MPPs to process them as required. This is similar in concept to the much later internet service daemon (inetd) in unix and other systems. The MCP is assembled by the user installation from a set of macros supplied by IBM. These macros define the lines and terminals comprising the system, the datasets required, and the procedures used to process received and transmitted messages. The MPPs, incorporating logic to process the various messages, are supplied by the installation, and use standard OS/360 or DOS/360 data management macros OPEN, CLOSE, GET, and PUT. PL/I includes the TRANSIENT file declaration attribute to allow MPPs to be written in a high-level language.

References

Other sources IBM. IBM System/360 Operating System Queued Telecommunications Access Method-Message Processing Program Services (PDF). C30-2003-4. IBM. IBM System/360 Disk Operating System--QTAM Message Processing Program Services. C30-5003. IBM. IBM System/360 Disk Operating System QTAM Message Control Program. C30-5004.

Worked examples

Example 1 — a first encounter with Queued Telecommunications Access Method

Start with the simplest possible case. Write down what Queued Telecommunications Access Method 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 Queued Telecommunications Access Method 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 Queued Telecommunications Access Method 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 Queued Telecommunications Access Method

In research: Queued Telecommunications Access Method 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 Queued Telecommunications Access Method 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: Queued Telecommunications Access Method is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer network stubs, IBM mainframe operating systems, Mainframe computer stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Queued Telecommunications Access Method 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 Queued Telecommunications Access Method in 20 minutes

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

Frequently asked questions

What is Queued Telecommunications Access Method in simple terms?

Why does Queued Telecommunications Access Method 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 Queued Telecommunications Access Method?

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 Queued Telecommunications Access Method.