computer science

Runtime system

Runtime system 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 Runtime system rather than just read about it. In short: In computer programming, a runtime system or just runtime is a sub-system that exists in the computer where a program is created, as well as in the computers where the program is intended to be run. The name comes from the compile time and runtime division from compiled languages, which similarly distinguishes the computer processes involved in the creation of a program (compilation) and its execution in the target…

Key takeaways

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

Reference excerpt

In computer programming, a runtime system or just runtime is a sub-system that exists in the computer where a program is created, as well as in the computers where the program is intended to be run. The name comes from the compile time and runtime division from compiled languages, which similarly distinguishes the computer processes involved in the creation of a program (compilation) and its execution in the target machine (the runtime). A runtime environment (RTE) is the context in which a runtime operates. Most programming languages have some form of runtime system that provides an environment in which programs run. This environment may address a number of issues including the management of application memory, how the program accesses variables, mechanisms for passing parameters between procedures, interfacing with the operating system (OS), among others. The compiler makes assumptions depending on the specific runtime system to generate correct code. Typically the runtime system will have some responsibility for setting up and managing the stack and heap, and may include features such as garbage collection, threads or other dynamic features built into the language.

Overview Every programming language specifies an execution model, and many implement at least part of that model in a runtime system. One possible definition of runtime system behavior, among others, is "any behavior not directly attributable to the program itself". This definition includes putting parameters onto the stack before function calls, parallel execution of related behaviors, and disk I/O. By this definition, essentially every language has a runtime system, including compiled languages, interpreted languages, and embedded domain-specific languages. Even API-invoked standalone execution models, such as Pthreads (POSIX threads), have a runtime system that implements the execution model's behavior. Most scholarly papers on runtime systems focus on the implementation details of parallel runtime systems. A notable example of a parallel runtime system is Cilk, a popular parallel programming model. The proto-runtime toolkit was created to simplify the creation of parallel runtime systems. In addition to execution model behavior, a runtime system may also perform support services such as type checking, debugging, or code generation and optimization.

Relation to runtime environments The runtime system is also the gateway through which a running program interacts with the runtime environment. The runtime environment includes not only accessible state values, but also active entities with which the program can interact during execution. For example, environment variables are features of many operating systems, and are part of the runtime environment; a running program can access them via the runtime system. Likewise, hardware devices such as disks or DVD drives are active entities that a program can interact with via a runtime system. One unique application of a runtime environment is its use within an operating system that only allows it to run. In other words, from boot until power-down, the entire OS is dedicated to only the application(s) running within that runtime environment. Any other code that tries to run, or any failures in the application(s), will break the runtime environment. Breaking the runtime environment in turn breaks the OS, stopping all processing and requiring a reboot. If the boot is from read-only memory, a secure, single-mission system is created. Examples of such directly bundled runtime systems include:

Between 1983 and 1984, Digital Research offered several of their business and education applications for the IBM PC on bootable floppy diskettes bundled with SpeedStart CP/M-86, a reduced version of CP/M-86 as runtime environment. Some stand-alone versions of Ventura Publisher (1986–1993), Artline (1988–1991), Timeworks Publisher (1988–1991) and ViewMAX (1990–1992) contained special runtime versions of Digital Research's GEM as their runtime environment. In the late 1990s, JP Software's command line processor 4DOS was optionally available in a special runtime version to be linked with BATCOMP pre-compiled and encrypted batch jobs in order to create unmodifiable executables from batch scripts and run them on systems without 4DOS installed.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Runtime system

Start with the simplest possible case. Write down what Runtime system 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 Runtime system 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 Runtime system 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 Runtime system

In research: Runtime system 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 Runtime system 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: Runtime system is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computing platforms, Runtime systems, so understanding it makes those chapters shorter.
In everyday life: Look for Runtime system 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 Runtime system in 20 minutes

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

Frequently asked questions

What is Runtime system in simple terms?

Why does Runtime system 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 Runtime system?

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 Runtime system.