Browse Prior Art Database

Use of Multiple Communications Methods

IP.com Disclosure Number: IPCOM000034781D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Related People

Andersen, PR: AUTHOR [+5]

Abstract

When a DOS extension that supports multiple communications programs is loaded, all interrupt vectors that support communications interfaces are tested for a "signature" that identifies each communication program. The search order is part of the DOS extension but may be overridden through the use of a parameter specified when loading the DOS extension. By saving information that indicates the communication program type, the specifics of using that communication program can be accommodated. This also allows multiple communications programs to be used simultaneously. (Image Omitted) Thus, when the user's application calls the DOS extension to do communications, the software being used to do the actual operation is hidden from the user and all communication methods look the same to the application program.

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Use of Multiple Communications Methods

When a DOS extension that supports multiple communications programs is loaded, all interrupt vectors that support communications interfaces are tested for a "signature" that identifies each communication program. The search order is part of the DOS extension but may be overridden through the use of a parameter specified when loading the DOS extension. By saving information that indicates the communication program type, the specifics of using that communication program can be accommodated. This also allows multiple communications programs to be used simultaneously.

(Image Omitted)

Thus, when the user's application calls the

DOS extension to do communications, the software being used to do the actual operation is hidden from the user and all communication methods look the same to the application program. In finding the loaded communications program(s), these steps are followed when the DOS extension is loaded: - Initialize the "loaded" interrupt value for each

Communications Program (CP) to 0 (Fig. 2), which means

"not loaded," since interrupt 0 is never valid.

- Search the list of valid interrupts for the

"signature" of each of the CPs supported.

- If a CP is loaded at an interrupt, save the

interrupt number in the table entry for this CP (Fig.

3).

- This indicates the CP is 'loaded' and which

interrupt to use when calling this CP. Otherwise,

check if one of the other supported CPs is loaded

at this interrupt. None of the CPs share an

interrupt.

- Save any request for a specific CP...