UNIX to DEC-10, a simple teleprocessing link

The objective of this thesis project was to create a software link between a PDP-11/34 minicomputer running under the UNIX operating system and a DECsystem-10 computer with the TOPS-10 operating system, both used at The University of Tennessee at Knoxville.

UNIX is a multi-user timesharing operating system developed at Bell Laboratories for the PDP-11 family of computers.

The software link provides the PDP-11 users the capability of batch job submission to the DEC-10. The hardware involved is minimal--either machine views the other as a simple terminal. The actual software that handles the communication is a simple process, not part of either operating system, per se.

A special device driver routine (added to the operating system) is necessary to handle the I/0 under UNIX. The existing device driver routine has a limited buffer size of 256 characters. The communication software which reads this buffer competes for machine resources at the same priority as other user processes. Therefore, a buffer overrun and consequent information loss can occur unless the output of the DEC-10 is automatically inhibited by the device driver until buffer space is available.

At any time, a user of the PDP-11 can submit a file of commands to be interpreted line by line by the communication software, which performs the requisite processing. This submission I merely results in the request being queued as a batch process, to be later initiated by an operator. When initiated by the operator, the queue of requests is serviced individually by first logging into the user's DEC-10 account (this information is system maintained). Any output produced by the DECsystem-10 is stored in a log file in the user's directory. The entire implementation is in the C language.