NOSS
NAS Operational Support System
The IBM 9020 ran the National Airspace System (NAS) program operationally. NAS consisted of the NAS Monitor (derived from OS/360 and written in BAL) and the ATC Application programs (written in JOVIAL). NAS is still in use today, though the S/360s are long gone!
This page is about NOSS – the NAS Operational Support System – which was used to maintain the NAS program. NOSS was developed in the 1960s and consists of a Monitor and various utility subprograms, the two main ones being a JOVIAL complier and a BAL assembler, called BALASM. This is regular BAL with the addition of the special 9020 instructions.
The original NAS program ran on a tape-only S/360 Model 50 complex. The Model 50s were selected by the FAA before the new S/360 family was announced to the public in 1964 (IBM had shared, in confidence, basic details of S/360 the previous year). Development of NOSS ran in parallel to the development of IBM’s mainstream Operating Systems. As the first 9020s were tape-only, NOSS is probably very similar to TOS/360 (Tape Operating System/360).
Disks were later added to all 9020s and many Model 50 complexes were upgraded to use Model 65s as the main processor. With the advent of disks, the support OS evolved into OS/9020, almost identical to OS/360, but NOSS was retained as it could run in a tape-only subsystem. This was useful because an offline sub-system without disks could be configured out of an operational triplex system.
NAS software development took place at the FAA's NAFEC facility, where there were three separate 9020 complexes (A, D, and E versions). As NAFEC was non-operational a whole system could be scheduled to run the OS/9020 support system without any regard to redundancy, etc. However, certain NAS support functions had to be run at the operational centres. An example is the Prefiled Flight Plan Assembly utility, which created a tape of repetitive flight plans (unique at each centre) for subsequent input to the operational system. The tape-only NOSS could be used for this as it didn't require disks.
There were three tape sub-systems, any one of which could be configured into the offline system without significantly impacting the operational system’s redundancy. [This is a slight over-simplification as an offline sub-system only had access to two tape channels - see below. Exactly which two channels depended on which one of the three I/O Control Element was configured into the offline system. Note that only one of the two accessible tape controllers would be actually configured into the offline system via the special 9020 hardware Configuration Control Register that every major element contained.]
NOSS will run on a standard S/360 as well as a 9020. The NOSS Monitor determines it is running on a standard S/360 if it takes a program interrupt when executing the special 9020 instruction Load Identity (LI) and proceeds accordingly. [In standard S/360 the LI instruction didn't exist so trying to execute it caused an invalid instruction program interrupt.] As 9020 was a multiprocessor system each S/360 Compute Element (CE) was physically jumpered with a different identity. Since a program in storage could be executed by any CE in the system, it was sometimes necessary for the program to identify which CE is executing the program. This was particularly essential in connection with the task of reallocating the work load following a change in job priorities or a failure of some part of the system. The LI instruction provided a means for a program to load a value characteristic of the CE by which it was being executed. CE-1, CE-2, CE-3, and CE-4 took the identifying values of 0, 1, 2, and 3 respectively.
NOSS went through several iterations as the 9020 system itself evolved, but was stable by 1974 and there were no further changes until the 9020 was replaced in the early 1990s.
NOSS Documents
NOSS BALASM Subprogram Design Document
NOSS Executable Tape Dump
When the UK 9020 system was decommissioned, I saved about forty tapes that I thought would be useful in the future. In 2012 I started to dump these tapes using a Kennedy 9600 tape drive attached to a PC with a Pertec interface. This tape drive could read the 800 BPI NRZI format the tapes were written in on the 9020’s IBM 2401 tape drives.
Unfortunately, about a third of the way through the forty tapes the Kennedy tape drive developed a fault which prevented further tape reading. However, I had already dumped an IPL’able (“bootable” in non-S/360 language) executable NOSS tape before the failure. This is a picture of the tape and the data transfer setup:
Before dumping the binary contents of the tape, the PC program reads through the tape to analyse the format. The output of this analysis pass is a log file (in plain text) showing the details of the files on tape and the blocks within the files. In the case of the NOSS tape there are 29 files, with various quantities (up to 16) and sizes of blocks within each file. Here is the log file:
Then the PC program dumps each binary file as a single file containing all that file’s blocks. These are contiguous files with no indication of the start or finish of individual file blocks. The analysis pass log file has to be used to derive that information. I have archived the 29 binary NOSS files into a single zip file. Here is the archive file:
Here (thanks to the good offices of Tony Lawrence) is a tape image of the NOSS tape in a format suitable for use with the SIMH S/360 simulator:
In 1998 I downloaded the archived NOSS source code from our VM/370 bureau system. This was onto a PC running terminal emulation, and the files were converted from EBCDIC to ASCII in the process. I then ZIP’ed them into two separate ZIP files (why I split them into two files I don’t now recall). The source files are in Symbolic Program Tape (SPT) format, which is just plain text. Here are these ZIP files:
This is an alphabetical listing of the 74 zipped files:
30/09/1998 13:38 15,252 BALCP42A.SPT
29/09/1998 20:51 173,020 BANLZ.SPT
30/09/1998 14:31 240,998 BATCH.SPT
29/09/1998 21:01 118,244 BATCH1.SPT
30/09/1998 13:38 32,800 BATCHCP.SPT
30/09/1998 13:43 109,388 BBAL.SPT
30/09/1998 13:44 20,746 BBRKP.SPT
30/09/1998 13:45 72,160 BCONM.SPT
29/09/1998 20:49 214,512 BCONV.SPT
30/09/1998 13:45 67,568 BEXVL.SPT
30/09/1998 13:43 24,518 BFUNC.SPT
29/09/1998 20:50 7,462 BIOG2.SPT
30/09/1998 13:43 11,398 BLIST.SPT
05/10/1998 21:32 78,310 BLKSRT.SPT
30/09/1998 13:44 97,170 BOPLK.SPT
30/09/1998 13:48 316,192 BPAS1.SPT
29/09/1998 20:47 400,898 BPAS2.SPT
29/09/1998 20:50 106,108 BPRNT.SPT
30/09/1998 13:44 9,348 BSLKP.SPT
30/09/1998 13:38 2,624 BTSTRP.SPT
05/10/1998 22:31 88,560 CARD.SPT
29/09/1998 21:08 379,660 CHART.SPT
29/09/1998 20:09 121,442 CMDCONVT.SPT
29/09/1998 20:10 72,078 CMDIAG.SPT
29/09/1998 20:04 293,560 CMMAIN.SPT
29/09/1998 20:09 585,644 CMPH1.SPT
05/10/1998 22:26 162,360 CMPH1A.SPT
29/09/1998 21:04 296,266 CMPLST.SPT
05/10/1998 22:26 328 CZXCOM.SPT
05/10/1998 22:26 328 CZXTABLZ.SPT
30/09/1998 13:42 76,424 INSCT2.SPT
30/09/1998 13:41 222,384 INSECT.SPT
29/09/1998 20:53 323,326 JOV.SPT
29/09/1998 20:36 540,298 JOV1.SPT
29/09/1998 20:17 207,870 JOV1A.SPT
29/09/1998 20:19 153,668 JOV2A.SPT
29/09/1998 20:20 230,338 JOV2A1.SPT
29/09/1998 20:23 297,414 JOV2A2.SPT
29/09/1998 20:01 815,162 JOV2A3.SPT
29/09/1998 20:02 99,056 JOV2AG.SPT
29/09/1998 20:58 358,914 JOV2D.SPT
29/09/1998 20:59 120,048 JOV3A.SPT
29/09/1998 20:30 341,612 JOV3B.SPT
29/09/1998 20:31 110,208 JOV3C.SPT
29/09/1998 20:32 105,452 JOV3T.SPT
29/09/1998 20:51 656 JOVBOOT.SPT
29/09/1998 20:41 419,266 JOVDATA.SPT
29/09/1998 20:32 27,798 JOVDG.SPT
29/09/1998 20:14 337,512 JOVEXEC.SPT
29/09/1998 20:16 263,466 JOVEXPR.SPT
29/09/1998 20:54 108,896 JOVFM.SPT
29/09/1998 20:38 186,468 JOVINIT.SPT
29/09/1998 20:43 230,502 JOVPROC.SPT
29/09/1998 20:55 87,330 JOVXR.SPT
30/09/1998 13:41 16,154 LNM.SPT
30/09/1998 13:38 1,804 LODER50A.SPT
30/09/1998 13:34 113,160 LSTGN.SPT
30/09/1998 14:29 1,037,054 MONT123B.SPT
30/09/1998 13:38 490,278 MONT223A.SPT
30/09/1998 13:33 25,420 OBJBLR.SPT
05/10/1998 21:32 16,154 SF0774.SPT
05/10/1998 21:33 84,870 SIMCP13A.SPT
05/10/1998 21:34 142,926 SIMLA.SPT
05/10/1998 22:30 460,102 SIMNR.SPT
05/10/1998 21:35 212,134 SIMPR.SPT
30/09/1998 13:39 160,556 SPTOUT.SPT
05/10/1998 22:31 80,770 TAPES.SPT
05/10/1998 22:30 21,156 UBSFS.SPT
29/09/1998 20:32 1,312 WORKZ.SPT
29/09/1998 21:05 149,158 XREF.SPT
29/09/1998 20:51 328 ZXBFRS.SPT
05/10/1998 22:26 328 ZXCOM.SPT
30/09/1998 13:43 7,708 ZXMASTER.SPT
29/09/1998 20:51 328 ZXTABLZ.SPT
74 File(s) 12,804,710 bytes