Editing TRS-80 (section)

== Software ==
=== BASIC ===
Three versions of the [[BASIC]] programming language were produced for the Model I. ''[[Level I BASIC]]'' fits in 4 KB of [[read-only memory|ROM]], and ''Level II BASIC'' fits into 12 KB of ROM. Level I is single precision only and had a smaller set of commands. Level II introduced double precision floating point support and has a much wider set of commands. Level II was further enhanced when a disk system was added, allowing for the loading of ''Disk BASIC''.{{r|thomas1977}}

Level I BASIC is based on [[Li-Chen Wang]]'s free [[Tiny BASIC]] with more functions added by Radio Shack.{{r|leininger19770917}} The accompanying ''User's Manual for Level 1'' by David A. Lien presents lessons on programming with text and cartoons. Lien wrote that it was "written specifically for people who don't know anything about computers ... I want you to have fun with your computer! I don't want you to be afraid of it, because there is nothing to fear".<ref name="lien1977">{{Cite book |url=https://archive.org/stream/Level_1_Users_Manual_1977_David_Lien#page/n0/mode/2up |title=User's Manual for Level 1 |last=Lien |first=David A. |date=1978 |page=1}}</ref>{{r|fylstra197804}} Reviewers praised the manual's quality.{{r|thomas1977}}{{r|yeager197908}}{{r|archer198310}} Level I BASIC has only two [[string (computer science)|string]] variables (<code>A$</code> and <code>B$</code>), 26 numeric variables (<code>A</code> – <code>Z</code>), and one array, <code>A()</code>. Code for functions like SIN(), COS() and TAN() is not included in ROM but printed at the end of the book. The only error messages are "<code>WHAT?</code>" for syntax errors, "<code>HOW?</code>" for arithmetic errors such as [[division by zero]], and "<code>SORRY</code>" for [[out of memory]] errors.

Level I BASIC is not [[tokenized]]; reserved words are stored literally. In order to maximize the code that fits into 4 KB of memory, users can enter abbreviations for reserved words. For example, writing "<code>P.</code>" instead of "<code>PRINT</code>" saves 3 bytes.

Level II BASIC, introduced in mid-1978, was licensed from [[Microsoft]] and is required to use the expansion bus and disk drives. Radio Shack always intended for Level I BASIC to be a stopgap until Level II was ready, and the first brochure for the Model I in January 1978 mentioned that Level II BASIC was "coming soon". It is an abridged version of the 16K [[Microsoft BASIC|Extended BASIC]], since the Model I has 12 KB of ROM space. According to [[Bill Gates]], "It was a sort of intermediate between 8K BASIC and Extended BASIC. Some features from Extended BASIC such as descriptive errors and user-defined functions were not included, but there were double precision variables and the PRINT USING statement that we wanted to get in. The entire development of Level II BASIC took about four weeks from start to finish." The accompanying manual is more terse and technical than the Level I manual. Original Level I BASIC-equipped machines could be retrofitted to Level II through a ROM replacement performed by Radio Shack for a fee (originally $199). Users with Level I BASIC programs stored on cassette have to convert these to the tokenized Level II BASIC before use. A utility for this was provided with the Level II ROMS.

Disk BASIC allows disk I/O, and in some cases ([[NewDos/80]], MultiDOS, DosPlus, LDOS) adds powerful sorting, searching, full-screen editing, and other features. Level II BASIC reserves some of these keywords and issues a "<code>?L3 ERROR</code>", suggesting a behind-the-scenes change of direction intervened between the creation of the Level II ROMs and the introduction of Disk BASIC.

Microsoft also marketed an enhanced BASIC called [[Microsoft Level III BASIC programming language|Level III BASIC]] written by Bill Gates,<ref>{{cite book |title=Program Instructions for Level III BASIC |date=1979 |publisher=Microsoft Consumer Products |page=1}}</ref> on cassette tape.  The cassette contains a "Cassette File" version on one side and a "disk file" version on the second side for disk system users (which was to be saved to disk).<ref>{{cite book |title=Program Instructions for Level III BASIC |date=1979 |publisher=Microsoft Consumer Products |page=11}}</ref> Level III BASIC adds most of the functions in the full 16 KB version of BASIC plus many other TRS-80 specific enhancements.  Many of Level III BASIC's features are included in the TRS-80 Model III's Level II BASIC and disk BASIC.

Level I BASIC was still offered on the Model I in either 4K or 16K configurations after the introduction of Level II BASIC.

=== Other programming languages ===
Radio Shack published a combined assembler and program editing package called the Series I Assembler Editor.<ref name="auto">{{cite web |title=1982 Radio Shack Computer Catalog RSC-6 page 11 |url=https://www.radioshackcatalogs.com/flipbook/c1982_rsc-06.html?fb3d-page=11 |website=Radio Shack Catalogs dot com |publisher=Tandy/Radio Shack |access-date=December 1, 2022}}</ref> ''[[80 Micro]]'' magazine printed a modification enabling it to run under the Model 4's TRSDOS Version 6. Also from Radio Shack was Tiny Pascal.<ref>{{cite web |title=1982 Radio Shack Computer Catalog RSC-6 page 9 |url=https://www.radioshackcatalogs.com/flipbook/c1982_rsc-06.html?fb3d-page=9 |website=Radio Shack Catalogs dot com |publisher=Tandy/Radio Shack |access-date=May 1, 2019}}</ref>

Microsoft made its [[Fortran]], [[COBOL]] and BASCOM [[BASIC]] compiler available through Radio Shack.<ref name="auto"/>

In 1982, [[Scientific Time Sharing Corporation]] published a version of its [[APL (programming language)|APL]] for the TRS-80 Model III as APL*PLUS/80.<ref>{{cite journal |last=Gates |first=Phelps |date=March 1983 |title=A microcomputer APL*PLUS system implementation| journal=ACM SIGAPL APL Quote Quad |volume=13 |issue=3 |pages=201–204 |doi=10.1145/390005.801217|doi-access=free }}</ref>

=== Other applications ===
[[Blackjack]] and [[backgammon]] came with the TRS-80, and at its debut, Radio Shack offered four payroll, personal finance, and educational programs on cassette.{{r|thomas1977}}{{r|rscat1977}}{{rp|3}}{{r|white198708}} Its own products' quality was often poor.{{r|green198212}} A critical 1980 ''[[80 Micro]]'' review of a [[text adventure]] described it as "yet another example of Radio Shack's inability to deal with the consumer in a consumer's market". The magazine added, "Sadly, too, as with some other Radio Shack programs, the instructions seem to assume that the reader is either a child or an adult with the mentality of a slightly premature corned beef".<ref name="obrien198008">{{cite magazine |url=https://archive.org/stream/80-microcomputing-magazine-1980-08/80Microcomputing_0880#page/n19/mode/2up |title=Pyramid |magazine=[[80 Micro]] |date=August 1980 |issue=8 |access-date=February 12, 2015 |author=O'Brien, William |pages=21}}</ref>

The more than 2,000 Radio Shack franchise stores {{as of|1982|09|lc=y}} sold third-party hardware and software, but the more than 4,300 company-owned stores were at first prohibited from reselling or even mentioning products not sold by Radio Shack itself.<ref name="shuford198002">{{cite magazine |url=https://archive.org/stream/80-microcomputing-magazine-1980-02/80Microcomputing_0280#page/n35/mode/2up |title=The Bottom Shelf: Software For All Seasons |magazine=[[80 Micro]] |date=February 1980 |issue=2 |access-date=October 17, 2013 |author=Shuford, Dan B. |pages=36–37}}</ref><ref name="green198108">{{Cite magazine |last=Green |first=Wayne |author-link=Wayne Green |date=August 1981 |title=Tandy Growth Retarded |url=https://archive.org/details/80-microcomputing-magazine-1981-08/page/n9 |magazine=[[80 Micro]] |issue=20 |page=10 |access-date=2019-05-28}}</ref><ref name="shea19820913">{{Cite magazine |last=Shea |first=Tom |date=1982-09-13 |title=All others sell at list price; we deal |url=https://books.google.com/books?id=EDAEAAAAMBAJ&pg=PA11 |magazine=[[InfoWorld]] |volume=4 |issue=36 |page=11 |access-date=2019-03-17}}</ref>{{r|green198212}}{{r|pournelle198307}}{{r|white198708}} Green stated in 1980 that although "there are more programs for the 80 than for all other systems combined" because of the computer's large market share, "Radio Shack can't advertise this because they are trying as hard as they can to keep this fact a secret from their customers. They don't want the TRS-80 buyers to know that there is anything more than their handful of mediocre programs available", many of which "are disastrous and, I'm sure, doing tremendous damage to the industry".<ref name="green198008">{{cite magazine |url=https://archive.org/stream/80-microcomputing-magazine-1980-08/80Microcomputing_0880#page/n7/mode/2up |title=80 Remarks |magazine=[[80 Micro]] |date=August 1980 |issue=8 |access-date=February 12, 2015 |author=Green, Wayne |author-link=Wayne Green |pages=8}}</ref><ref name="green198011">{{cite magazine |url=https://archive.org/stream/kilobaudmagazine-1980-11/Kilobaud_Microcomputing_1980_November#page/n5/mode/2up |title=Publisher's Remarks |magazine=Kilobaud |date=November 1980 |issn=0192-4575 |access-date=June 23, 2014 |author=Green, Wayne |author-link=Wayne Green |pages=6–8}}</ref> [[Broderbund]], founded that year, began by publishing TRS-80 software, but by 1983 cofounder [[Doug Carlston]] said that the computer "turned out to be a terrible market because most of the distribution networks were closed, even though there were plenty of machines out there".<ref name="barry198310">{{Cite magazine |last=Barry |first=David |date=October 1983 |title=Profiles: The Carlston Trio |url=https://www.atarimagazines.com/v2n7/CarlstonTrio.html |magazine=Antic |access-date=2021-07-01}}</ref> Green wrote in 1982 that Apple had surpassed Tandy in sales and sales outlets despite the thousands of Radio Shack dealers because it supported third-party development, while "we find the Shack seeming to begrudge any sale not made by them and them alone".<ref name="green198212">{{Cite magazine |last=Green |first=Wayne |author-link=Wayne Green |date=December 1982 |title=Is the Shack in real trouble? |url=https://archive.org/details/80_Micro_1982-12_1001001_US/page/n7/mode/2up |magazine=[[80 Micro]] |type=editorial |pages=8, 10, 12 |access-date=2020-02-29}}</ref> Dealers not affiliated with Radio Shack preferred to sell software for other computers and not compete with the company; mail-order sales were also difficult, because company-owned stores did not sell third-party publications like ''80 Micro''.{{r|green198108}}{{r|white198708}}

Charles Tandy reportedly wanted to encourage outside developers but after his death a committee ran the company, which refused to help outside developers, hoping to monopolize the sale of software and peripherals.{{r|white198708}} Leininger reportedly resigned because he disliked the company's bureaucracy after Tandy's death.{{r|markoff19811005}} An author wrote in a 1979 article on the computer's "mystery of machine language graphics control" that "Radio Shack seems to hide the neat little jewels of information a hobbyist needs to make a treasure of the TRS-80". He stated that other than the "excellent" Level I BASIC manual "there has been little information until recently ... TRS-80 owners must be resourceful", reporting that the computer's "keyboard, video, and cassette" functionality were also undocumented.<ref name="yeager197908">{{Cite magazine |last=Yeager |first=George H |date=August 1979 |title=Exploring TRS-80 Graphics |url=https://archive.org/stream/byte-magazine-1979-08/1979_08_BYTE_04-08_LISP#page/n81/mode/2up |magazine=[[Byte (magazine)|Byte]] |volume=4 |issue=8 |pages=82–84}}</ref> The first book authorized by Tandy with technical information on TRSDOS for the Model I did not appear until after the computer's discontinuation.{{r|pournelle198307}}

By 1982, the company admitted—after no software appeared for the Model 16 after five months—that it should have, like Apple, encouraged third-party developers of products like the [[killer app]] [[VisiCalc]].<ref name="markoff19820705">{{cite magazine |url=https://books.google.com/books?id=MjAEAAAAMBAJ&pg=PA36 |title=Radio Shack: set apart from the rest of the field |magazine=[[InfoWorld]] |date=July 5, 1982 |volume=4 |issue=26 |access-date=February 10, 2015 |author=Markoff, John |author-link=John Markoff| pages=36}}</ref>{{r|white198708}} (A lengthy 1980 article in a Tandy publication introducing the TRS-80 version of VisiCalc did not mention that the spreadsheet had been available for the Apple II for a year.<ref name="reed">{{cite web |url=http://www.trs-80.org/visicalc/ |title=VisiCalc |publisher=TRS-80.org |access-date=23 January 2015 |author=Reed, Matthew}}</ref>) However, in the early 1980s, it was not uncommon for small companies and municipalities to write custom programs for computers such as the TRS-80 to process a variety of data. In one case a small town's vehicle fleet was managed from a single TRS-80.<ref>{{cite magazine|first=Jeff |last=Clack |title=Vehicle Maintenance - How the City of Lander, WY keeps tracke on their Model III |url=https://archive.org/details/80-U.S._Volume_VI_Number_04_1983-04_80-Northwest_Publishing_US/page/n85?q=%22Lander%2C+Wy%22 |magazine=80-U.S. |publisher=80-Northwest Publishing |date=April 1, 1983 |access-date=October 9, 2019}}</ref>

By 1985, the company's Ed Juge stated that other than [[Scripsit]] and [[DeskMate]], "we intend to rely mostly on 'big-name', market-proven software from leading software firms".{{r|juge198510}} A full suite of office applications became available from the company and others, including the VisiCalc and [[Multiplan]] spreadsheets and the [[Lazy Writer]], [[Electric Pencil]], and from Radio Shack itself the Scripsit and SuperScripsit word processors.<ref>{{cite web |title=1982 Radio Shack Computer Catalog RSC-6 page 10 |url=https://www.radioshackcatalogs.com/flipbook/c1982_rsc-06.html?fb3d-page=10 |website=Radio Shack Catalogs dot com |publisher=Tandy/Radio Shack |access-date=December 2, 2022}}</ref>

Compared to the contemporary Commodore and Apple micros, the TRS-80's block graphics and crude sound were widely considered limited. The faster speed available to the game programmer, not having to processor color data in high resolution, went a long way to compensating for this. TRS-80 arcade games tended to be faster with effects that emphasized motion. This perceived disadvantage did not deter independent software companies such as [[Big Five Software]] from producing unlicensed versions of arcade games like Namco's ''[[Galaxian]]'', Atari's ''[[Asteroids (video game)|Asteroids]]'',<ref>{{cite web |title=Super Nova |url=http://www.trs-80.org/super-nova/ |website=TRS-80 dot org |publisher=Matthew Reed |access-date=December 1, 2022}}</ref> [[Taito]]'s ''[[Lunar Rescue]]'', [[WMS Industries|Williams]]'s ''[[Make Trax]]'',{{r|dobson20121126}} and Exidy's ''[[Targ (video game)|Targ]]''<ref name="williams198109">{{cite magazine |url=https://archive.org/stream/byte-magazine-1981-09/BYTE_Vol_06-09_1981-09_Artifical_Intelligence#page/n385/mode/2up |title=Big Five Software |magazine=[[Byte (magazine)|Byte]] |volume=6 |issue=9 |date=September 1981 |access-date=October 19, 2013 |author=Williams, Gregg |pages=384–386}}</ref> and ''[[Venture (video game)|Venture]]''. Sega's ''[[Frogger]]'' and ''[[Zaxxon]]'' were ported to the computer and marketed by Radio Shack.<ref name="radioshackcatalogs.com">{{cite web |title=Radio Shack Computer Catalog RSC-12 page 31 |url=https://www.radioshackcatalogs.com/flipbook/c1985_rsc-12.html?fb3d-page=031 |website=radioshackcatalogs dot com |publisher=Tandy/Radio Shack |access-date=December 2, 2022}}</ref>{{r|dobson20121126}} Namco/Midway's ''[[Pac-Man]]'' was cloned by Philip Oliver and distributed by Cornsoft Group as ''[[Scarfman]]''.{{r|dobson20121126}}<ref>{{cite web |title="Software" Category - page 4: Scarfman |url=http://www.trs-80.org/category/software/page/4/ |website=TRS-80 dot org |publisher=Matthew Reed |access-date=May 8, 2019}}</ref> Atari's ''[[Battlezone (1980 video game)|Battlezone]]'' was cloned for the Models I/III by Wayne Westmoreland and Terry Gilman and published by [[Adventure International]] as ''Armored Patrol''.<ref>{{cite web |title=Armored Patrol |url=http://www.trs-80.org/armored-patrol/ |website=TRS-80 dot org |publisher=Matthew Reed |access-date=May 7, 2019}}</ref> They also cloned ''Eliminator'' (based on [[Defender (1981 video game)|''Defender'']]) and ''[[Donkey Kong (arcade game)|Donkey Kong]]'';<ref>{{cite web |title=Search Results for "eliminator", Donkey Kong |url=http://www.trs-80.org/?s=eliminator |website=TRS-80 dot org |publisher=Matthew Reed |access-date=May 8, 2019}}</ref> the latter wasn't published until after the TRS-80 was discontinued, because [[Nintendo]] refused to license the game.{{r|dobson20121126}}

Some games originally written for other computers were ported to the TRS-80. ''[[Microchess]]'' has three levels of play and can run in the 4 KB of memory that is standard with the Model&nbsp;I; the classic ''[[ELIZA]]'' is another TRS-80 port. Both were offered by Radio Shack.{{r|dobson20121126}}<ref name="auto1">{{cite web |title=1982 Radio Shack Computer Catalog RSC-6 page 8 |url=https://www.radioshackcatalogs.com/flipbook/c1982_rsc-06.html?fb3d-page=08 |website=radioshackcatalogs dot com |publisher=Tandy/Radio Shack |access-date=December 2, 2022}}</ref> ''[[Apple Panic]]'', itself a clone of Universal's ''[[Space Panic]]'', was written for the TRS-80 by Yves Lempereur and published by Funsoft.<ref>{{cite web |title="Software" Category - page 5: Apple Panic |url=http://www.trs-80.org/category/software/page/5/ |website=TRS-80 dot org |publisher=Matthew Reed |access-date=May 8, 2019}}</ref> [[Epyx]]{{'}}s ''[[Temple of Apshai]]'' runs slowly on the TRS-80.{{r|dobson20121126}} [[Infocom]] ported its series of interactive text-based adventure games to the Models I/III; the first, ''[[Zork|Zork I]]'', was marketed by Radio Shack.<ref name="radioshackcatalogs.com"/>{{r|dobson20121126}}

[[Adventure International]]'s text adventures began on the TRS-80,{{r|dobson20121126}} as did ''[[Sea Dragon (video game)|Sea Dragon]]'' by Westmoreland and Gilman, later ported to the other home micros.{{citation needed|date=May 2019}} ''[[Android Nim]]'' by Leo Christopherson was rewritten for the Commodore PET and Apple.{{citation needed|date=May 2019}} Many games are unique to the TRS-80, including ''Duel-N-Droids'',<ref>{{cite web |title=Duel-N-Droids |url=https://videogamegeek.com/videogame/142683/duel-n-droids |website=videogamegeek dot com |publisher=BoardGameGeek, LLC |access-date=May 14, 2019}}</ref> also by Christopherson, an early [[first-person shooter]] ''13 Ghosts'' by Software Affair (the Orchestra-80, -85 and -90 people)<ref>{{cite magazine |last1=Mitchell |first1=Robert |magazine=[[80 Micro]] |title=Ghost Busting |date=November 1984|page=192 |url=https://archive.org/details/80-microcomputing-magazine-1984-11/page/n193/mode/2up|publisher=CW Communications |access-date=July 15, 2020}}</ref><ref>{{cite web |title=13 Ghosts (TRS-80) |url=https://www.mobygames.com/game/13-ghosts |website=mobygames dot com |publisher=Blue Flame Labs |access-date=May 14, 2019}}</ref><ref>{{cite web |title=1985 Radio Shack Computer Catalog RSC-14 page 36 |url=https://www.radioshackcatalogs.com/flipbook/c1985_rsc-14.html?fb3d-page=36 |website=radioshackcatalogs dot com |publisher=Tandy/Radio Shack |access-date=December 2, 2022}}</ref> and shooters like ''[[Cosmic Fighter]]'' and ''[[Defence Command (video game)|Defence Command]]'',{{citation needed|date=May 2019}} and strange experimental programs such as Christopherson's ''Dancing Demon'',<ref name="dobson20121126">{{Cite web |url=https://www.gamedeveloper.com/business/games-from-the-trash-the-history-of-the-trs-80 |title=Games from the Trash: The History of the TRS-80 |last=Dobson |first=Dale |date=2012-11-26 |website=Gamasutra |language=en |access-date=2019-05-13}}</ref><ref>{{Cite web|url=http://www.dnull.com/demon/|title=Dancing Demon|website=www.dnull.com}}</ref> in which the player composes a song for a devil and choreographs his dance steps to the music.<ref name="byte198105">{{cite magazine |url=https://archive.org/stream/byte-magazine-1981-05/1981_05_BYTE_06-05_Software_Piracy#page/n149/mode/2up |title=Dancing Demon from Radio Shack |magazine=[[Byte (magazine)|Byte]] |volume=6 |issue=5 |date=May 1981 |access-date=October 18, 2013 |author1=Cooper, Elizabeth |author2=Kolya, Yvon |pages=148}}</ref> Radio Shack offered simple graphics animation programs ''Micro Movie'' and ''Micro Marquee'', and ''Micro Music''.<ref name="auto1"/>

Radio Shack offered a number of programming utilities, including an advanced debugger, a subroutine package, and a cross-reference builder.<ref>{{cite web |title=Radio Shack Computer Catalog RSC-7 page 9 |url=https://www.radioshackcatalogs.com/flipbook/c1982_rsc-07.html?fb3d-page=09 |website=radioshackcatalogs dot com |publisher=Tandy/Radio Shack |access-date=December 2, 2022}}</ref> Probably the most popular utility package was Super Utility written by Kim Watt of Breeze Computing.<ref>{{cite web |title=Super Utility |url=http://www.trs-80.org/super-utility/ |website=TRS-80 dot org |publisher=Matthew Reed |access-date=May 7, 2019}}</ref> Other utility software such as [[Bill Stewart (programmer)|Stewart Software's]] Toolkit offered the first sorted directory, decoding or reset of passwords, and the ability to eliminate parts of TRSDOS that were not needed in order to free up floppy disk space. They also produced the On-Line 80 BBS, a TRSDOS-based Bulletin Board System. Misosys Inc. was a prolific producer of sophisticated TRS-80 utility and language software for all models of TRS-80 from the very beginning.<ref>{{cite web |title=Misosys 1992 Catalog page 1 |url=http://www.tim-mann.org/trs80/doc/TRS-80%20Software%20and%20Hardware%20from%20MISOSYS,%20Inc..pdf |website=tim-mann dot org |publisher=Roy Soltoff/Misosys Inc. |access-date=May 8, 2019}}</ref>

Perhaps because of the lack of information on TRSDOS{{r|pournelle198307}} and its bugs,{{r|white198708}} by 1982 perhaps more operating systems existed for the TRS-80 than for any other computer.<ref name="archer198212">{{cite magazine |url=https://archive.org/stream/byte-magazine-1982-12/1982_12_BYTE_07-12_Game_Plan_1982#page/n393/mode/2up |title=Multidos / A New TRS-80 Disk Operating System |magazine=[[Byte (magazine)|Byte]] |volume=7 |issue=12 |date=December 1982 |access-date=February 6, 2015 |author=Archer, Rowland Jr. |pages=392–397}}</ref> TRSDOS is limited in its capabilities, since like Apple DOS 3.3 on the [[Apple II]], it is mainly conceived of as a way of extending BASIC to support disk drives. Numerous alternative DOSes appeared, the most prominent being [[Logical Disk Operating System|LDOS]] because Radio Shack licensed it from Logical Systems and adopted it as its official DOS for its Models I and III hard disk drive products. Other alternative TRS-80 DOSes included [[NewDos/80|NewDOS]] from [[Apparat, Inc.]], and [[DoubleDOS]], [[DOSPlus]], [[MicroDOS]], [[UltraDOS]] (later called Multidos). The DOS for the Model 4 line, TRSDOS Version 6, was produced by and licensed from Logical Systems. It is a derivative of LDOS, enhanced to allow for the new Model 4 hardware such as its all-RAM architecture (no ROM), external 32 KB memory banks, bigger screen and keyboard, and featured new utilities such as a ram disk and a printer spooler.

The memory map of the Model I and III render them incompatible with the standard [[CP/M]] OS for Z80 business computers, which loads at [[hexadecimal]] address $0000 with TPA ([[Transient Program Area]]) starting at $0100; the TRS-80 ROM resides in this address space. Omikron Systems' Mappers board remaps the ROM to run unmodified CP/M programs on the Model I. A customized version of CP/M is available but loses its portability advantage.{{r|pournelle198007}}<ref>Theresa Welsh, David Welsh ''Priming the Pump: How TRS-80 Enthusiasts Helped Spark the PC Revolution'', The Seeker Books, 2007, {{ISBN|0979346819}}, Chapter 2 ''The DOS Wars''</ref> ''80 Micro'' magazine published a do-it-yourself CP/M modification for the Model III.<ref>{{cite magazine |last1=Brewer |first1=Bill |magazine=[[80 Micro]] |title=CP/M Cheap |date=March 1983 |issue= |pages=112–122 |url=https://archive.org/details/80-microcomputing-magazine-1983-03/page/n111/mode/2up |publisher=CW Communications |access-date=July 19, 2020}}</ref>