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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 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
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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