KEY CONCEPTS
Printer Server Task Perspective
The printer server task may be viewed as a "front end" to the pr inter task which is responsible for translating the message sent by the GOP process into the form expected by the printer task. The printer server loops through the following steps:
1.RECEIVE a message from the
2.When the message (a print object) is received, obtain an object selector for the message text.
3.Using the object selector, open a windoo onto the message text.
4.Copy the message text from 432 memory to PS memory through the open windON.
5.Close the window.
6.TRANSMIT a message with a reference to the pr int text to the printer task.
7.Repeat from step 1.
Printer Task (Device Task) Perspective
The printer task runs in an endless loop repeating the following steps:
1.ACCEPT a message from the print order mailbox;
2.Interpret the message; - - -
3.Transfer the data from the message to the printer, taking care of all device control (e.g., interrupts);
4.Update the status field of the print message with the
result of the operation; |
5.TRANSMIT the updated pr int_message to the pr int_response mailbox;
6.Repeat from step 1.
Printer Reply Task Perspective
The printer reply task may be viewed as a "back end" to the printer task. I t runs in an endless loop as follows:
1.ACCEPT a message from the print response mailbox.
1.Open a windON onto the print object in the 432 system.
2.Formulate a print reply message and deposit it in the print object through the openwindON.
3.Close the window.
4.SEND the print object to the printer reply port in the 432
system. -
5.Repeat from step 1.
