| Interactive Application System (IAS) | |
|---|---|
| Developer | Digital Equipment Corporation |
| OS family | RSX-11 |
| Working state | Discontinued |
| Initial release | 1975; 51 years ago (1975) |
| Latest release | 3.4 / May 1990; 35 years ago (1990-05) |
| Available in | English |
| Supported platforms | PDP-11 |
| Influenced by | RSX-11D |
| Default user interface | PDS or MCRCommand-line interface |
| License | Proprietary |
Interactive Application System (IAS) was aDEC operating system for thePDP-11.[1] It was afork fromRSX-11D.[2][3]
The last major release, Version 3.0, began distribution late 1979;[4] the final version, 3.4, came out May 1990.[1]
DEC's RSX-11A and C werepaper tape based, B had limited disk support, "D" was for disk, and the "M" designation was for "small Memory requirement" /later "Multi-user"[3] (with RSX-11M Plus being a followup).IAS was designed to a mix of "concurrent timesharing, real-time and batch."[5][6] Alooking back described it as "bare basics .. handled interrupts .. scheduled processes, and provided interprocess communications" without being "all things to all people."[7] Another description, rather than focusing on taking away overhead, wrote "IAS (Interactive Application System) was created by adding two things to 11D."[8]
RSX-11's use of aversion number as part of a file's identifier:MYFILE.DAT;3[9] was retained by IAS.[1]: p.2
Thebatch facility's command files used the same syntax as theindirect command files available to interactive users; multiple batch jobs could run concurrently.[1]: p.2 The system could be tuned to either leave unused CPU cycles to batch, or to guarantee a minimum level (without taking from Real Time requirements).[1]: p.1 [10]: p.28 [11]
IAS provided two different Command Language Interpreter (CLI) interfaces - theRSX-11 MCR, and the Program Development System (PDS). PDS was an early implementation of theDigital Command Language.[12][1]
DEC's Sort/Merge utility program was distributed as part of IAS.[1]: p.10
The system can be operated in one of threemodes: Real-Time, Multi-User, and Timesharing.[10]
Multi-User shares the system with Real-Time tasks;Timesharing adds effective concurrent use ofbatch processing alongside "noncritical real-time tasks" and interactive users.[10]: pp.10–13 Timesharing also addsTimesharing Control Primitives (TCP), described as a "mechanism for timesharing tasks to invoke and communicate with other timesharing tasks."[10]: p.13 An evaluation byTRW's Defense and Space Systems Group for Tactical Operations Analysis Support Facility atLangley AFB VA highlighted the "IAS heuristic timesharing scheduler" and "subtasking support at the Kernel Executive level via the SPAWN system directive."[10]: p.28
Theheuristic timesharing scheduler tracks "history of performance and degree of interaction."[10]: p.29
Some failure recovery is built into both the DEC hardware and IAS software.[13]
file systems, databases, .. etc were applications called by other applications
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