Device management techniques in OS

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            Device management

The main function of the device manager are :-
1. Monitor the status of all devices , including storage drives , printer and other peripheral.

2. Enforce pre-set policies on which process gets which device for how long.

3. Deal with the allocation of devices to processes.

4. Deal with the de- allocation of devices to processes ,both at a temporary basis (e.g. when the processes is interrupted) and on a permanent basis(e.g. when the processes is completed).
Example of devices.
1. Keyboard
2. Mouse 
3. Printer 
4. Monitor
5. Scanner
Etc.
There are three main type of devices:-
1. dedicated devices
2. Shared devices
3. Virtual devices

Dedicated device :-

These are devices that are assigned to one process at a time, and the processes only release once it is completed.

This make sense for devices like plotter and tape drives.

The problem with this is that it means only one user using it at a time, and it might be inefficient if the device isn't being used 100% of the time that it is being locked by user.

Shared device:-

These are the device that can be shared between several processes.

Considering an example like hard disk, it is shared but interleaving between different process request.

All conflicts for device need to resolved but pre- determined policies to decide which request is handled first.

Virtual device:-

These are devices are a combination of dedicated and shared devices.

So a printer is a dedicated device but using the spooling means it can be shared.

A print job isn't sent straight to the printer ,instead it goes to the disk(spool) untill it is fully  prepared with all the necessary printer sequences and formatting, then it goes to the printer , ensuring that the printer and all I/o devices are used efficiently.


Thank you viewers..

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