TRS-80 DOS - LDOS (Logical Systems Disk Operating System)

LDOS 5.1 Manual (Logical Systems)

Radio Shack Edition (1982)

LDOS Quarterly, July 1981

LDOS is a disk operating system for the TRS-80 Model I and Model III. It was developed in 1980-81 from Randy Cook's VTOS 4.0, sold from 1981 by Logical Systems, Inc. (LSI) of Wisconsin, licensed by Radio Shack in 1982, and maintained from 1986 by MISOSYS, Inc., whose LDOS 5.3.1 of 1991 was the last release. Its 6.x successor, written for RAM-based machines, became TRSDOS 6 on the TRS-80 Model 4 and was later sold as LS-DOS.

LDOS was known for its device independence (any device could be linked, routed, filtered or set to a driver), its Job Control Language, its support of almost any mix of 5-inch, 8-inch and hard drives, full media interchange between the Model I and the Model III, a published supervisor call (SVC) interface for programmers, a manual of several hundred pages, and a support operation (toll-free line, update service, a CompuServe board and a quarterly newsletter) that no other TRS-80 DOS vendor of the time matched.

From VTOS to LDOS (1980-1981)

Lobo Drives International of Goleta, California, sold the LX-80, an expansion interface for the Model I that was not hardware compatible with the Radio Shack Expansion Interface, so Model I TRSDOS could not run on it. VTOS 4.0 had a second boot sector and code that let it run on both. In November 1980 Lobo signed a contract with Randy Cook that 80 Microcomputing (March 1981) described as giving Lobo "nonexclusive" but "total" rights to VTOS. The story of VTOS, and of Lobo's break with Cook, is on the VTOS page.

Unable to get the VTOS source code, Lobo hired Bill Schroeder's Galactic Software Ltd. (Mequon, Wisconsin) and Roy Soltoff's MISOSYS (Alexandria, Virginia) to fix VTOS, working from the machine code with Roy Soltoff's disassembler. Tim Mann, who had been disassembling and patching VTOS 4.0 on his own, was hired by Galactic soon after. The project grew from a bug fix for LX-80 owners into a new operating system for the whole TRS-80 market. The name originally stood for Lobo Drives (or Lobo Disk) Operating System; 80 Microcomputing reported that it was "a reassembled DOS incorporating several parts of the source code of Cook's VTOS", and Cook, who was to be paid royalties, objected that LDOS would be "head-on" competition for VTOS. According to Tim Mann, Cook was paid for his rights and acknowledged in the LDOS manual.

The manual of the 5.1 release credits the team as Bill Schroeder (Project Leader), Roy Soltoff (Systems Analyst), Chuck Jensen, Doug Kennedy, Dick Konop and Tim Mann. Tim Mann's own contributions included PR/FLT, the Model III RS-232 driver, parts of the Model I doubler driver, the BASIC extensions, the rewrite of the LX-80 ROM and CONV/CMD; he left in September 1981 for graduate school at Stanford.

LDOS was advertised in the February 1981 issue of 80 Microcomputing at $139 with the manual, and the March 1981 issue previewed the manual (over 200 pages in its preliminary form) with a mid-February release promised. The first LDOS 5.0 disks went out in the early spring of 1981. 80 Microcomputing's review in June 1981 (list price $149) called it "by far the best disk operating system (DOS) currently available for the Model I", while noting that the master disk had no Disk BASIC: the user copied BASIC from a TRSDOS 2.2 or 2.3 disk and LDOS patched it into LBASIC. VTOS 4.0 owners could get LDOS as a replacement for $40.

Logical Systems, Inc.

By July 1981 the rights to LDOS had passed to Logical Systems, Inc., a new Wisconsin corporation at 11520 N. Port Washington Road in Mequon (the same address as Galactic Software) whose principals were the people who had created LDOS. The name was chosen because it starts with an L, giving LDOS a second meaning. LSI had five full-time programmers and two support staff, and sold through four distributors: Lobo Drives (west), Galactic Software (central), MISOSYS (east) and Molimerx Ltd. of Bexhill, England (the Common Market). Owners got a toll-free support line, an update service (send in the master disk and a small fee), an LDOS board on CompuServe's MicroNET, and The LDOS Quarterly, whose first issue is dated July 1, 1981.

The Model III version (5.1.0) followed in July 1981 and the Model I 5.1.1 on November 30, 1981. LDOS 5.1 added a complete Disk BASIC, the two versions could read and write each other's disks, and from 5.1.2 on they had the same features. To make that possible LDOS 5.0.2 and later write only the X'FB' and X'F8' data address marks, which the Model III's 1793 controller can tell apart, instead of the X'FA' mark that Model I TRSDOS used for directory sectors.

Roy Soltoff owned one third of Logical Systems until a reorganization shortly before TRSDOS 6 was developed, and was the system designer of TRSDOS 6.0 (The MISOSYS Quarterly, Summer 1986). According to Tim Mann, Logical Systems later acquired Galactic Software. In April 1983 LSI moved into a 10,000 square foot building of its own at 8970 N. 55th Street, Brown Deer, Wisconsin, just north of Milwaukee.

Radio Shack and LDOS (1982)

In 1982 Radio Shack chose LDOS 5.1.3 as the operating system for its new hard drive system for the Model I and Model III (catalog 26-1130, a 5 megabyte drive that sold for $2,495). According to Tim Mann, it was Bill Schroeder who persuaded Tandy to license it. Radio Shack also sold the floppy version, LDOS 5.1.3 for the Model I (26-2213) and the Model III (26-2214), at $129, packaged with a Radio Shack edition of the LDOS 5.1 manual (copyright 1981, 1982 Logical Systems, "licensed in 1982 to Tandy Corp."). Radio Shack supported the copies it sold. The hard disk version, sold by Tandy as the Hard Disk Operating System, was later brought up to 5.1.4.

LDOS 6.0 becomes TRSDOS 6 (1983)

In October 1982 LSI announced a RAM-based LDOS, to reside below 3000H, called LDOS 6.0, with no upgrade path from 5.1. When Tandy released the TRS-80 Model 4 on April 26, 1983, its operating system, TRSDOS 6.0, was that system: the April 1983 LDOS Quarterly called it "the first appearance of an LDOS 6.0 type operating system" and said that the Model 4 Technical Reference Manual (26-2110) would document "TRSDOS 6.0 (which is LDOS 6.0)". LSI stressed that LDOS 5.1 and the 6.x systems were two separate product lines: 5.1 software ran on the Model 4 only in its Model III mode under LDOS 5.1. A Model II/12 version followed in 1984 as LS-DOS 6.2.0 (TRSDOS if bought through Tandy), and in 1984 LSI published the commented source code of LS-DOS/TRSDOS 6.2 as the three-volume THE SOURCE.

LSI's Later Years (1983-1988)

LDOS 5.1.4 (September 1983) was the last release by Logical Systems. In October 1983 The LDOS Quarterly became The LSI Journal; in January 1984 LSI announced that the Journal would continue as a section of the magazine BASIC Computing, which never happened; the April 1984 issue, printed by LSI itself when that fell through, is the last one known. In early 1984 LSI closed out the products it did not make itself and offered LDOS 5.1.4 at half price ($64.50) to anyone trading in NEWDOS/80 or DOSPLUS.

In March 1986 MISOSYS, by then in Sterling, Virginia, acquired the retail operation of Logical Systems, including the copyrights to the LSI product line (LDOS among them) and its registered customer database of 44,346 entries. TRSDOS 6 was not part of the sale. LSI released LS-DOS 6.3 for the Model 4 in 1987 and turned its distribution and support over to MISOSYS in July 1988.

The MISOSYS Years (1986-1994)

MISOSYS stopped the update service and sold fresh LDOS 5.1.4 disks instead, and moved LDOS support into The MISOSYS Quarterly (Summer 1986 to Summer 1993). Its LDOS 5.3 (1987), designed and prepared entirely by MISOSYS, extended the system date past 1987 to the end of 1999, added time stamps to the directory in the same form as LS-DOS 6.3 so that data disks could be shared with the Model 4, and brought the command syntax in line with the Model 4 DOS. It was released for the Model III (and the Model 4 in Model III mode) and the Lobo MAX-80 but not the Model I: MISOSYS asked for 1,000 prepaid orders before it would do a Model I version, and in Spring 1987 announced that there would be none.

In 1991 Roy Soltoff brought the Model III release in line with LS-DOS 6.3.1 and, reversing the 1987 decision, also produced "a true, official Model I release" of LDOS 5.3.1. Both were good through December 31, 2011. In 1992 MISOSYS published the LDOS & LS-DOS Reference Manual (M-40-060) and the LDOS & LS-DOS BASIC Reference Manual (M-40-061), which cover LDOS 5.3.1 and LS-DOS 6.3.1 in one book each. The MISOSYS Quarterly ended with its Summer 1993 issue, and MISOSYS closed down on March 1, 1994 (Matthew Reed, trs-80.org).

LDOS 5.3.1 for the Model I and Model III, LS-DOS 6.3.1 and the MAX-80 LDOS 5.1.3 are now on Tim Mann's site, which states that "LDOS/LS-DOS are available with the permission of William Schroeder."

How LDOS Numbers Its Versions

The October 1981 LDOS Quarterly explained the scheme using 5.0.2A as the example:

• 5 - the system. A change of this number is an entirely new system, with no updates or trade-ins (LDOS 6 was such a change).
• 0 - the series. A change is a new product with a new manual (5.0.x to 5.1.x); owners could trade up.
• 2 - the update: substantial patches or small new features, usually with replacement pages, for a small update fee.
• A - a maintenance letter for small patches; not always present.

LSI updated the master disk rather than selling a new package: the owner mailed in the master disk with the fee ($5 in 1981-82, $10 later, or $5 with the Extended Support Agreement) and got it back updated. Many updates were also printed as patches in the Quarterly, and the file dates on the master disk told which update a disk had.

Releases

Boot Screens

Model I

v5.0.0 (Lobo Drives)

v5.0.1 (Lobo Drives)

v5.0.2

v5.0.3

v5.1.1

v5.1.2 with SOLE (double density boot)

v5.1.3/R

v5.1.4

v5.3.1

Model III

v5.1.0

v5.1.3

v5.3.0

v5.3.1

Other Editions

• Radio Shack LDOS (1982): LDOS 5.1.3 in Radio Shack packaging, 26-2213 (Model I) and 26-2214 (Model III), $129, "virtually identical" to the LSI package (LDOS Quarterly, October 1982).
• Hard Disk Operating System: the LDOS 5.1.3 that Tandy licensed to run its 5 megabyte hard drive, later 5.1.4 with a revised hard disk driver. MISOSYS could not supply an upgraded HDOS; its LDOS 5.3 is a floppy product to which the owner adds the existing hard disk driver.
• smal-LDOS (1983): a subset of LDOS 5.1 for software vendors to distribute their programs on, sold in lots of 25. It kept the main library commands and most of BACKUP, FORMAT and CONV; FED and QFB were not included in smal-LDOS 5.1.4. LSI's WordStar for the Model I and III was supplied on smal-LDOS.
• Lobo LX-80 and MAX-80: LDOS came with Lobo's LX-80 interface and was the DOS of Lobo's MAX-80 computer (announced mid-1982). MISOSYS did a 5.3 release for the MAX-80 in 1986-87 from SYS0 source code that Les Mikesell had kept; the MAX-80 LDOS 5.1.3 is on Tim Mann's site.
• LDOS 6 / TRSDOS 6 / LS-DOS: not a version of LDOS 5 but the RAM-based successor described above (TRSDOS 6.0 on the Model 4 in 1983, LS-DOS 6.2 for the Model II/12, LS-DOS 6.3 in 1987 and 6.3.1 in 1990).

Disk images of the LDOS master disks, for use on real hardware or in an emulator. Each entry gives what that release brought; the Versions section has the full history.

Model I

Model III

LDOS 5.1.3 for the Lobo MAX-80, LDOS 5.3.1 and LS-DOS 6.3.1 are also on Tim Mann's MISOSYS page.

5.1.x, 2nd Edition

5.3 Upgrade Kit (1987)

Reference Manual (1992)

The LDOS manual was a tab-indexed binder in which updates were made by replacing pages. The 5.1 manual has the library commands, the utilities, the drivers and filters, Job Control Language, LBASIC and a technical section (memory map, SVCs, file and directory structures). For 5.3.0 MISOSYS supplied only change pages; the full 5.3.1 manual is the 1992 LDOS & LS-DOS Reference Manual, which covers the Model 4's LS-DOS 6.3.1 in the same book and marks where the two differ. Each title below is a download link.

LDOS 5.1 Manuals

LDOS 5.1 Updates

LDOS 5.3 (MISOSYS)

LS-DOS 6.3 (Model 4)

These are for the Model 4 successor of LDOS, filed on the site under LDOS.

Newsletters and Other Publications

• The LDOS Quarterly and The LSI Journal (Logical Systems, July 1981 - April 1984): release news, patches for every version and technical articles by the authors of LDOS.
• The MISOSYS Quarterly (Summer 1986 - Summer 1993): LDOS 5.3 and 5.3.1, LS-DOS 6.3 and the patches for them.
• Notes from MISOSYS (1983-1984).
• Software manuals: the LDOS Filter Package disks, the Powersoft Utility Disks and Toolbox for LDOS, and the other Logical Systems and MISOSYS products.

• LDOS v5.3.1 for the Model I Disassembled
• LDOS v5.3.1 for the Model III Disassembled

File Passwords

The password RS0LT0FF (with zeroes, not O's) is the master password of LDOS 5.3: it hashes to 113DH under the LDOS password algorithm and opens any protected file. CONV/CMD gives the files it writes the password P3UF, which has the same hash. The 5.3 update lists the owner passwords of the master disk as SYSTEM (/SYS files), BASIC (the BASIC files), FILTER (/FLT), DRIVER (/DVR), HELP (the HELP files) and UTILITY (all other /CMD files).

LDOS 5.0 used different passwords, which the first manual left out and the July 1981 LDOS Quarterly supplied: WOLVES for /SYS files, GSLTD for /DVR and /FLT files, RRW3 for /CMD files and LOBO/DCT, BASIC for the BASIC overlays and CCC for CONFIG/SYS.

Skipping the SYSGEN Configuration

Hold down CLEAR while resetting or powering up to boot without the configuration saved by SYSTEM (SYSGEN). This is the way out when a SYSGENed driver or filter keeps the system from working, and it is needed after updating a disk to 5.3: boot the updated disk with CLEAR held, then recreate and save the configuration.

Forcing CAPS Lock from a Program

Bit 5 of KFLAG$ (4423H on the Model I, 429FH on the Model III) is the CAPS lock bit. From BASIC on a Model III:

POKE(&H429F),PEEK(&H429F) OR 32     'CAPS lock on
							POKE(&H429F),PEEK(&H429F) AND 223    'normal upper/lower case

Use &H4423 on the Model I.

Clearing the Screen in a JCL File

MEMORY (GO=X'01C9') jumps to the ROM's clear-screen routine at 01C9H and returns to the DOS, so a JCL file can clear the screen (LDOS Quarterly, July 1981).

A One-Line Top-of-Form Program

BUILD with the HEX parameter can write a small program byte by byte. BUILD T/CMD (HEX) followed by the line 010700523E0CC33B0002020052 makes T/CMD: a load block that puts 5 bytes at 5200H, LD A,0CH / JP 003BH (the ROM's print-a-character routine), and a transfer address of 5200H. Running T sends a form feed to the printer; change the 0C to send another control code (LDOS Quarterly, July 1981).

Dates After 1999 and Disks for Older DOSes

• LDOS 5.1.x accepts dates only through December 31, 1987; 5.3.0 through 1999; 5.3.1 from 1980 through 2011, with 2000-2011 entered as 00-11.
• Convert older LDOS disks with DATECONV before using them under 5.3, and do not write to a converted disk with an earlier LDOS. Do not switch between a 5.3 system disk and an earlier one in drive 0 without rebooting.
• Under 5.3.1, RESET filespec (DATE=OFF) puts a file's directory entry back in the pre-5.3 form, for a file that has to go to an older DOS (for example through the TRSDOS 1.3 CONVERT utility).
• Programs that check the DOS version (RS-COBOL): the 5.3.1 README gives PATCH SYS0/SYS.SYSTEM:# (D02,8F=51:F02,8F=53), which changes OSVER$ at 441FH on the Model III.

Getting Files off a Model I TRSDOS Disk on a Model III

REPAIR makes a Model I TRSDOS disk readable on the Model III, but the Model III cannot write the old X'FA' data address mark back, so the disk can no longer be used by Model I TRSDOS. To leave the original untouched (LDOS Quarterly, January 1982):

1. Boot TRSDOS 1.3 and put the Model I disk in drive 1.
2. Use the TRSDOS CONVERT command to move the files to a TRSDOS 1.3 disk in drive 0.
3. Boot LDOS in drive 0 with the TRSDOS 1.3 disk in drive 1.
4. Use LDOS CONV to move the files from drive 1 to the LDOS disk.

More LDOS tips (custom and double-sided boot disks, host operation, the system files and what they do, configuring LDOS like NEWDOS/80) are on the DOS Tips page, and the unofficial zaps for LDOS are on the LDOS zap pages.