Buffering, Polling & Spooling

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Buffering

Kernels provide many services related to I/O. 

Several services—scheduling, buffering, caching, spooling, device reservation, and error handling—are provided by the kernel’s I/O subsystem and build on the hardware and device-driver infrastructure.

A buffer, of course, is a memory area that stores data being transferred between two devices or between a device and an application.

Caching: A cache is a region of fast memory that holds copies of data or cache is a temporary storage area where frequently accessed data can be stored for rapid access.

 What does Buffer mean?

A buffer is a temporary holding area for data while it's waiting to be transferred to another location. It is usually located in the RAM.
The concept of the buffer has developed in order to prevent data congestion from an incoming to an outgoing port of transfer.
 Computers have many different devices that all operate at varying speeds, and a buffer is needed to act as a sort of temporary placeholder for everything that is interacting.
This is done to keep everything running efficiently and without issues between all the devices, programs, and processes running at that time.

Buffering is done for three reasons:

One reason is to cope with a speed mismatch between the producer and consumer of a data stream.

A second use of buffering is to provide adaptations for devices that have different data-transfer sizes.

A third use of buffering is to support copy semantics for application I/O.

Ex: Print command , Download from Net....

Spooling (Buffer jobs)

Spooling stands for Simultaneous peripheral operation online. A spool is a similar to buffer as it holds the jobs for a device till the device is ready to accept the job. 

It considers disk as a huge buffer which can store as many jobs for the device till the output devices are ready to accept them.

Buffering use limited area in main memory while Spooling uses the disk as a huge buffer.

Video cards send images to a buffer before they are displayed on the screen (known as a screen buffer).

Double buffering is a term used to describe a device that has two buffers. ... 

Definition of: double buffering. double buffering. A programming technique that uses two buffers to speed up a computer that can overlap I/O with processing. 

Data in one buffer are being processed while the next set of data is read into the other one.

For example, with graphics, double buffering can be used to show one image or frame while a separate frame is being buffered to be shown next. 

This method makes animations and games look more realistic than the same done in a single buffer mode.

What is Polling?

The state of continuous monitoring is known as polling.

Interrupt:

An interrupt is like a shopkeeper. If one needs a service or product, he goes to him and apprises him of his needs. In case of interrupts, when the flags or signals are received, they notify the controller that they need to be serviced.

Polling:

The polling method is like a salesperson. The salesman goes from door to door while requesting to buy a product or service. Similarly, the controller keeps monitoring the flags or signals one by one for all devices and provides service to whichever component that needs its service.

For example, when a printer is connected via a parallel port, the computer waits until the printer has received the next character.

1. The software utility is installed separately

true/false

2. device controller maintains 

a. local buffer storage 

b. cache 

c. address table

d. all the above

3. operating systems have a single device driver -true/false

 4. The devices are assigned to one process at a time

a. tabe drive

b. hard disk

c. Q

d. pooling

5. A buffer, is a memory area that stores data 

true/false

6. Caching: that holds copies of data---true /false

7.Buffering is a services, provided by------?

a. Kernal

b. API

c. Memory pointer

c. none of the above

8. Buffer is usually located in the 

a. ROM

b. RAM

C. memory

9. buffer prevent data congestion in network--t/f

 

10. buffer is needed to act as a sort of

a. temporary placeholder

b. register

c. boot strap memory

d. spolling

 Answer:

1.true

2.a

3. false

4.a

5. true

6. true

7. a

8. RAM. 

9. true

10.a