TSX-Plus is a multi-user operating system for the PDP-11/LSI-11 series of computers. It was developed by S&H Computer Systems, Inc. and is based on DEC's RT-11 single-user real-time operating system (TSX-Plus installs on top of RT-11).
Overview
The system is highly configurable and tunable.
Due to the constraints of the memory management system in the PDP-11/LSI-11, the entire operating system core must occupy no more than 40 kibibytes of memory, out of a maximum possible 4 mebibytes of physical memory that can actually be installed in those machines (mandated by the 22-bit address space). The strength of TSX-Plus is to simultaneously provide to multiple users the services of DEC's single-user RT-11. Depending on which PDP-11 model and the amount of memory, the system could support a minimum of 12 users (14-18 users on a 2Mb 11/73, depending on workload). A productivity feature called "virtual lines" "allows a single user to control several tasks from a single terminal."
The software included a WP package named Lex-11 and a spreadsheet from Saturn Software. The machine slowed considerably if more than 8 students wanted to use the word-processing package at the same time. There was also a decision-table language called "D" from the NCC in Manchester which worked very well on TSX Plus.
History
Released in 1980, TSX-Plus was the successor to TSX, released in 1976.