biology

System generation

System generation is a biology 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 System generation rather than just read about it. In short: In computing system generation or sysgen is the process of creating a particular unique instance of an operating system by combining user-specified options and parameters with manufacturer-supplied general-purpose program code to produce an operating system tailored for a particular hardware and software environment. The term is primarily used when referencing older mainframe and minicomputer operating systems.

Key takeaways

System generation belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect System generation to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of System generation from memory before moving on to harder problems.

Reference excerpt

In computing system generation or sysgen is the process of creating a particular unique instance of an operating system by combining user-specified options and parameters with manufacturer-supplied general-purpose program code to produce an operating system tailored for a particular hardware and software environment. The term is primarily used when referencing older mainframe and minicomputer operating systems. Some other programs have similar processes, although not usually called "sysgen." For example, IBM's Customer Information Control System (CICS) was installed through a process called CICSGEN.

Rationale A large general-purpose program such as an operating system has to provide support for all variations of Central processing unit (CPU) that it might be run on, for all supported main memory sizes, and for all possible configurations of input/output (I/O) equipment. No one installation requires all this support, so system generation provides a process for selecting the options and features actually required on any one system. Sysgen produces a system that is most efficient in terms of CPU time, main memory requirements, I/O activity, and/or disk space. Often these parameters can be traded off, for example to generate a system that requires less memory at the expense of increased disk I/O operations.

Examples The Burroughs large systems Master Control Programs (MCP) were written in high-level ALGOL-like languages ESPOL or NEWP. The MCP is tailored by coding $OMIT conditional-compilation pragmas, which conditionally bypass compilation of specified pieces of code. IBM System/360 Disk Operating System (DOS) was written in assembler. The systems programmer performing the sysgen codes assembler macros specifying the desired options and assembles the supervisor. IBM OS/360 has a two-step procedure called Stage I and Stage II. In Stage I the programmer specified the options for the system in a set of macros and assembled them. The output of Stage I was a job stream which contains the job control to perform all the necessary assemblies, link edits, and to create the required system libraries and copy the necessary modules into them. IBM Network Control Program (NCP) and Emulation program (EP) for the IBM 3705 have two-step procedures similar to that of OS/360. RSX-11M had a three-phase SYSGEN that was required to add new hardware to the base executive.

Worked examples

Example 1 — a first encounter with System generation

Start with the simplest possible case. Write down what System generation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 System generation 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 System generation 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 System generation

In research: System generation appears in biology 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 System generation 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: System generation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Operating system stubs, System software, so understanding it makes those chapters shorter.
In everyday life: Look for System generation 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 System generation in 20 minutes

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

Frequently asked questions

What is System generation in simple terms?

Why does System generation matter?

Because it connects several biology 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 System generation?

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 System generation.