Understanding the operating system

THE OPERATING SYSTEM IN THREE KEY IDEAS

When I start an application to play a video, the images appear on the screen and sound comes out of the speakers. And at the same time my mail reader warns me of the arrival of a new message to which I can answer, by entering text with the keyboard, without having to leave my video player (which would oblige me perhaps to start again the reading from the beginning while I’m finally going to know how the hero will get away with it!?). How can an application interact with hardware devices? How can two applications run at the same time on a single processor? It is thanks to the operating system, an intermediate software layer between the application layer and the material layer, that we propose you to discover in three key concepts …

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GLOSSARY

• Operating System (OS): English expression meaning « operating system ». Set of programs that manage the use of computer hardware resources by applications that are launched there: memory and hard disk storage resources, processor compute resources, communication resources to devices or over the network. The operating system either accepts or denies these requests, and then reserves the resources in question to prevent their use from interfering with other requests from other software. (Source: Wikipedia)
• Application: An application or an application is, in the computer field, a program (or a software package) directly used by the user to perform a task, or a set of elementary tasks of the same domain or forming a whole. Typically, a text editor, a web browser, a media player, a video game, are applications. (Wikipedia source)
• Memory: an electronic device used to store data (values, program instructions). In a computer, there are three main types of memory external to the processor: the random access memory (RAM) (card connected to the motherboard), the read only memory (ROM) (integrated circuit to the motherboard) and the mass memory ( hard drives, and other peripheral storage media). The processor also integrates several levels of memory, including the cache memory (placed in the chip that contains the processor) and the registers (internal to the processor).
• Virtual memory: mechanism that allows to simulate the presence of a type of memory by using another type (for example a hard disk). It is used for example to simulate the presence of RAM using mass memory. (Wikipedia source)
• Process: The form that a program takes when it is run within an operating system. A process instance typically includes: a set of instructions (often copied to RAM from the hard drive), a place, called an address space, reserved in RAM for storing the data it handles, and resources hardware and software that the program uses. (Wikipedia source)
• Scheduler: A software component of the operating system that is responsible for allocating processor time to processes. The choice of the elected process to execute on the processor at a given time is done by a scheduling procedure and involves managing the context changes.

ABOUT THE AUTOR

Damien Saucez is Inria Research Scientist in the DIANA team. His research focuses on information-centric networking (ICN) (eg, routing and congestion control issues), Software Defined Networking (SDN) (for example, issues of resilience and robustness), and large-scale experiments.It is an active contributor to IETF and FTIR.