Spooling technology and channels for printer sharing

The role of spooling technology:
1, the introduction of spooling technology is to easing the contradiction between high-speed CPUs and low-speed I/O devices;
2, spooling technology can allow more than one external device for online concurrent operation, Achieve Virtual Nature;

In this technology used to buffer and channel, buffer everyone is more familiar with, here do not introduce, here is a simple introduction to the channel.

Channel:
1, the introduction of channel technology makesparallel operation of CPU and peripherals is possible; 
2, the channel can be regarded as a specialized I/O processor, it can realize the peripheral and main memory directly exchange data;
3, CPU and channel relationship:
(1) in the instruction system using the channel mode, there is a set of channel instructions dedicated to the channel. When I am I/O operation, the CPU only needs to start the channel, then can continue to execute its own program, the channel executes the Channel program, management and implementation of I/O operations;

(2) The whole system is divided into two levels of management, the level of CPU to channel management, level Two is the channel to the control of equipment management;

Spooling Systems and Channels:

spooling to implement Printer sharing:

The steps to implement printer sharing in spooling technology are as follows:

Note: The SPO here refers to the output process.

The steps for the printer to actually print the flowchart:

Spooling technology and channels for printer sharing