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Software levels

Interrupt handlers

The Interrupt Service Routines (ISRs) are short routines designed to turn the asynchronous events from devices (and controllers)into synchronous ones that the operating system can deal with in time. While an ISR is executing, some set of interrupts is usually blocked, which is adangerous state of affairs that should be avoided as much as possible.

ISRs generally encode the information about the interrupt into some queue that the OS checks regularly - e.g. on a contextswitch.

Device drivers

Device drivers are primarily responsible for issuing the low-level commands to the hardware that gets the hardware to do whatthe OS wants. As a result, many of them are hardware dependent.

Conceptually, perhaps the most important facet of device drivers is the conversion from logical to physical addressing. The OS maybe coded in terms of logical block numbers for a file, but it is the device driver that converts such logical addresses to real physical addresses andencodes them in a form that the hardware can understand.

Device drivers may also be responsible for programming smart controllers, multiplexing requests and de-multiplexingresponses, and measuring and reporting device performance.

Device independent os code

This is the part of the OS we've really been talking the most about. This part of the OS provides consistent device namingand interfaces to the users. It enforces protection, and does logical level caching and buffering.

In addition to providing a uniform interface, the uniform interface is sometimes pierced at this level to expose specific hardwarefeatures -- CD audio capabilities, for instance.

The device independent code also provides a consistent error mode to users, letting them know what general errors occurredwhen the device driver couldn't recover.

User code

Even the OS code is relatively rough and ready. User libraries provide simpler interfaces to I/O systems. Good examples are thestandard I/O library that provides a simplified interface to the filesystem. printf and fopen are easier to use than write and open. Specifically suchsystems handle data formatting and buffering.

Beyond that there are user level programs that specifically provide I/O services (daemons). Such programs spool data, ordirectly provide the services users require.

Files, disk management

File: a named collection of bits stored on disk. From the OS' standpoint, the file consists of a bunch of blocks stored on the device.Programmer may actually see a different interface (bytes or records), but this does not matter to the file system (just pack bytes into blocks, unpack themagain on reading).

Common addressing patterns:

  • Sequential: information is processed in order, one piece after the other. This is by far the most common mode: e.g. editor writes out new file,compiler compiles it, etc.
  • Random Access: can address any record in the file directly without passing through its predecessors. E.g. the data set for demand paging, alsodatabases.
  • Keyed: search for records with particular values, e.g. hash table, associative database, dictionary. Usually not provided by operating system. TLBis one example of a keyed search.

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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Source:  OpenStax, Operating systems. OpenStax CNX. Aug 13, 2009 Download for free at http://cnx.org/content/col10785/1.2
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