Return to Floodgap Retrobits' Tandy! Pocket! Mania!
[PC-4-san.]

TPM: Tandy Radio Shack TRS-80 Pocket Computer PC-1 and PC-3, and Tandy Pocket Computer PC-8

As the Bible says, so shall the first be last and the last first (or something), and so it is with the Sharp-sourced Tandy Pocket Computers as the PC-1 introduced the line and the PC-8 concluded it, despite the Casio interlopers PC-4/5/6/7 jumping in the middle.

With the exception of the PC-2, all of the Sharp-built Tandy Pocket Computers use S'-BASIC, a single-byte tokenizing system with a limited set of commands. S'-BASIC (as opposed to S-BASIC, the larger variant which was used in other Sharp Pocket Computers but only used by Tandy in the PC-2), which Tandy dubbed "Pocket BASIC," introduces several key conceits of Pocket Computer programming that even influenced Casio. The first and most obvious change is that BASIC is a two-headed chimaera, split into a pure RUNtime mode where calculations can be entered in freely (as if it were a calculator) and programs can be executed, but not edited; and a PROgram (or WRiTe) mode with a simple editor where programs are entered, changed and overwritten, but no immediate mode statements can be processed. This allowed easy switching of behaviour without increasing cost or complexity. Secondly, S'-BASIC also established the convention of a fixed baseline variable space, where variables A-Z (or A$-Z$) were defined as a baseline, double variables weren't allowed (no simultaneous use of A and A$) and arrays were actually aliases to other variables within the space (such that A(1) was the same as B). Both of these modes carried over into their descendants and into the Casio models; although the S'-BASIC was upgraded with various small changes, the base interpreter remained essentially unchanged, allowing the line to be broadly cross-compatible (or at least upwardly so). All Sharp systems had single programming spaces; to mitigate this limitation, programs could be subdivided with one touch access to labels using the "DEF" key -- for example, DEF followed by A jumped to label "A" in the BASIC text. Although useful for creating menus, this approach was definitely less elegant than the segmented program spaces of the later Casio units.

Interestingly, none of the Sharp-based Tandy Pocket Computers (except the PC-2) has a lower-case mode.

Despite being the elders of the line, there is still much to recommend the Sharp units, and with the exception of the PC-8, the Sharps (including the incompatible but obscenely powerful PC-2) demonstrate generally good design and decent performance in a small package -- exactly what we would expect from a Pocket Computer.

Remember: in the computer option descriptions, M = memory expansion (with maximum available), T = cassette tape interface, P = printer interface, S = serial interface. Lists of non-Tandy peripherals and options are not guaranteed to be exhaustive. MSRPs best guess from available contemporary catalogues.


[The PC-1 family. Click the picture for an enlarged view.]

Tandy Radio Shack TRS-80 Pocket Computer PC-1

26-3501
Introduced 1980
Originated as Sharp PC-1211
CPU: SC43177/SC43178 dual 4-bit CPUs @ 256kHz
LCD: 24 character, non-dot-addressable
OS: S'-BASIC
Base memory (free/total bytes): 1424/1920
Size: 175x70x15mm, 170g (0.3lb)
Options: T, P

[The PC-1 (26-3501). Click the picture for an enlarged view.]

Tandy Radio Shack TRS-80 Pocket Computer PC-1

The first Tandy Pocket Computer was certainly a bombshell to the American market -- here was something more powerful than the usual clearance-box desktop calculator, something you could program and do stuff with in the palm of your hand! [You are slowly getting used to operating the Keys.] Just get used to squeezing it all into that little keyboard, and you're set!

Tandy seemed to know that they were releasing something a little hard for the casual computerist to grasp. We don't blink an eye today at an iPhone or a Palm Pilot, but in 1980 Sharp had to work hard to shake the calculator stereotype ("A truly pocket-sized Computer (not a programmable calculator)," asserts the manual; "since this is such a radically new product and most people won't know how or where to start ..."). To that end, giving it its own dialect of BASIC, even a relatively small one, was a key advancement setting it on apparent par with larger contemporary desktop systems since they, too, were often programmed in BASIC.

As stated above, the PC-1 was the standard-setter for the dual-mode BASIC we see on every Pocket Computer, along with its inventive method of variable management to make the most of the small space available, and if one wanted a larger array you could make a bigger one referenced as Z() by taking program space away. Although the arithmetic was very good for its class, string management was best described as inadequate, mostly due to a very sparse implementation lacking several key operators and their eight-character length which was set in stone, something Sharp would try to remedy in future models. The PC-1 also established the peculiar "dot abbreviation" convention of Sharp BASIC: where an abbreviated instruction was followed by a literal period (.); any instruction could be abbreviated to its unique portion, which was a little dubious for things like SI. and CO. but was fairly useful for longer keywords like PRINT (P.) and RETURN (R.). Entry was made even more convenient with the Reserve Keys function, essentially a macro-keys facility where any of a set of keys (the bottom two alpha rows, minus ENTER) could be programmed with text up to a combined total of 48 bytes. Debugging was essentially token, but the DEBUG command did allow rudimentary tracing.

The PC-1 is interesting for its dual-CPU architecture, but this should not be considered a parallel CPU architecture. The CPUs are basically the same core with different (mask?) ROM for different features and handle different services, switching execution back and forth; Roman von Wartburg believes this occurred because one single CPU was simply not enough to hold the entirety of BASIC and the BIOS, which seems plausible. Indeed, the dual CPU approach was never repeated outside of the PC-121x line.

Tape being the dominant (and cheapest) method of mass storage open to most hobbyists, Tandy simultaneously released the PC-1 with a rebadged Sharp cassette interface for $49, powered by AA batteries. Cassette support was very complete -- even reserve keys could be saved to tape! The cassette-printer interface, the first one to establish the regrettable convention of NiCad usage (greatly limiting its longevity in the present era), came later and is not documented in the baseline manual. This 16CPL 5x7-pin dot-matrix printer used its own unique ribbon cartridges and retailed for a reasonable $149.95, although the initial impression of good value would probably evapourate once you'd waxed the battery. If you find one of these printers, make sure you get plenty of ribbon since it's not always easy to come by. It is somewhat inexplicable why a 24-character display would be chained to a 16-character printer, however.

Tandy wanted to establish its line off right and released a bucket of home-grown software packages on tape along with the launch covering a wide variety of applications from games to statistics and business and personal finance. These packages are difficult to find nowadays, particularly in intact condition with manuals, but the move was an extremely sound one at the time and it is surprising that Tandy did not do this more with later Pocket Computer releases. Most were under $20. There were even a few books released by Tandy specifically for the PC-1, both of them republished and store-branded titles.

There is a fault with the PC-1 that was not apparent during its days of existence but is of great concern to collectors -- over time, many PC-1 LCDs will gradually darken around the traces, and some will turn almost completely black. This seems to be caused by inadequate sealing around the LCD assembly causing the crystals to gradually dehydrate and become opaque with time. If you are looking for a PC-1 to purchase, inspect the display carefully and pick a unit that looks as clear as possible. Fortunately, it does not seem to affect all units as there are many that are still pristine.

Although an exceptional first start, the PC-1 is still largely outclassed by the majority of its successors in just about every metric including size, memory and performance. Nevertheless, this should not be considered an intrinsic failing, merely the natural progression of a design where this unit was clearly the prototype, and at the time a practically revolutionary one. Indeed, the extremely easy availability of the PC-1 on the used market should bear ample testimony to the number that were sold. Tandy discontinued the model in 1983.

Here are the Tandy options/catalogue numbers and their Sharp equivalents for the PC-1:

Other sites on the PC-1:



[The PC-3 family. Click the picture for an enlarged view.]

Tandy Radio Shack TRS-80 Pocket Computer PC-3

CPU: SC61860 (CMOS 8-bit) @ 576kHz
LCD: 24 character, non-dot-addressable
OS: S'-BASIC (24K ROM)
Size: 135x70x9.5mm, 115g (0.25lb)
Options: T, P

[The original PC-3 (26-3590). Click the picture for an enlarged view.] 26-3590
Introduced 1983
Originated as Sharp PC-1250
Base memory (free/total bytes): 1438/2048

[The 'fat' 4K PC-3 (26-3589). Click the picture for an enlarged view.] 26-3589
Introduced 1984
Originated as Sharp PC-1251
Base memory (free/total bytes): 3486/4096

Tandy Radio Shack TRS-80 Pocket Computer PC-3

With the PC-3, Tandy cloned their smallest Pocket Computer yet and as such the one most deserving of the name; the PC-1 needed deep shorts to accomodate it, and the PC-2 was positively acromegalic. Even the just slightly preceding PC-4 looked buff by comparison.

Best of all, despite its considerably smaller size, it is still a Pocket Computer with Punch; how much Punch is currently a matter of some research and debate, however. ['I'd better remember this, too.'] Most resources agree that its clock speed is 576kHz, a nice bump over the PC-1, except that the (admittedly embryonic) PC-1251 MESS driver insists on a more pedestrian 192. Tandy also in their official specifications for the units insisted that an additional 0.2K of RAM was present in the total, an assertion that appears in no other references; it isn't at all clear where this is coming from, although it may possibly represent a contribution from whatever RAM is buried in the display controller. (The memory specs I have presented are purely based on RAM chip presence.)

Whatever the real numbers, it did the job and it fit in your pocket. The PC-3 took all the PC-1's best features, including the screen, reservable keys and definable keys, and put them into a faster, smaller and sleeker package. Free memory was about the same, but didn't get any worse for size, and in 1983 the MSRP of $99.95 was a steal. In addition, the PC-3 had an upwardly compatible BASIC, strongly based on many facets of the PC-2's -- while tapes saved on a PC-1 could be read into a PC-3 as-is, PC-3 programs could take advantage of added support for READ/DATA/RESTORE, WAIT, RANDOM, INKEY$ and PASSword protection, while DEBUG was changed out for the more typical TRON/TROFF. Strings and array support were greatly improved with a new two-dimensional DIM, and arrays other than A() were independent and did not alias other variables (but the only array that could be used as a second subscript was, strangely, A()); in addition, DIM not only controlled array size but allowed string expansion with constructions like DIM B$(3)*12, which creates four (0-3) 12-character strings. Strings defaulted to 16 characters, but could be as long as 80. The glitch with 2-D array subscripting must have escaped the notice of the manual authors because it was hastily published on an easily-misplaced slip of paper after the manual's initial publication.

The presence of the PC-3 really helped bring old PC-1 users back into the fold, especially with the incompatibilities of the PC-2 and PC-4. Really, there were only two small stains on the PC-3: the fact that available free memory really didn't improve much, and the loss of the PC-1's peripheral port. I call these "small stains" because the latter was largely mitigated by the large variety of Sharp peripherals that the PC-3 was compatible with, and the memory constraint was tremendously lightened with the 4K PC-3 "PC-3A" released in 1984. (One "thing that makes you go hmm" is the lower catalog number for the later release ... perhaps releasing the 4K PC-3 was something Tandy was planning from the beginning?) Tandy also simultaneously released their own thermal printer and tape interface for an MSRP of $119.95, finally with a 24CPL width, bringing the PC-3's peripheral availability to par with its older relative.

The 4K PC-3 was the first Pocket Computer to lose the Radio Shack designation, becoming merely the Tandy Pocket Computer PC-3, or PC-3A as it appeared in some catalogues. Replacing its predecessor completely, the 4K PC-3 "PC-3A" lasted until 1986.

[The PC-3 and the Sharp CE-126 printer/cassette interface.] The PC-3, along with the PC-2 and PC-4, easily represents the best of what Pocket Computers have to offer. In fact, although the PC-4 beats the PC-3 in cost and convenience and the PC-2 just crushes everything under its raw oozing muscle, the 4K PC-3 makes a decently fast, amply provisioned, good all-around system -- especially when paired up with all the compatible peripherals Sharp made and Tandy didn't import! Many people will talk in reverent tones about the Sharp CE-125, a very cleverly designed printer and microcassette recorder combination which looks super-neat in its matching case, but unfortunately was another evil NiCad-based contraption that I have recently learned works well to prop my closet open ('cuz when the battery goes toes up it sure don't do squat else). Instead, I rave about the Sharp CE-126P, another cassette/printer combo which can be powered with AA batteries, using the same thermal printer paper as the PC-3's own native printer. This stylish portable device is not hard to find on the used market -- I own two, both purchased from eBay originally -- and because it is a relatively unknown device does not command a large price. A PC-3 and a CE-126 are a hard-to-beat combination for a small desktop print terminal or for running printed tallies off of calculations, and the built-in cassette interface is a nice bonus. Need something to run off raffle tickets? Need to spin out numbers on paper without waiting for Excel or Mathematica to start up? Want a receipt printer that's a little more than an adding machine? You can't beat this combo for size or convenience.

Another outstanding find, but a tough one, is the small 2.5" CE-140F pocket floppy drive. Although the media is weird, you get a comfy 64K per side, enough to jam just about anything you want on a single disk. Finally, the (much later) EA-128C and EA-129C can be used as a link cable between the PC-3 and any Sharp system with the same 11-pin I/O.

The long and short of it is, for a great combination of size, expandability and function, the PC-3 definitely deserves consideration by anyone who wants a Pocket Computer that can "do real stuff."

The cross-platform MESS multiple systems emulator has a driver for the PC-1251, which will work for PC-3 emulation, of course.

The pinout for the 11-pin I/O connector is as follows (pin 1 starting from the top of the machine). They should be 5v TTL levels, but I am not responsible if you fry your machine, so test carefully.

  1. MT 2 (optional input from peripheral)
  2. Ground
  3. VCC
  4. Busy
  5. Data Out (typically for printer)
  6. Cassette Out (a/k/a X out)
  7. Cassette In (a/k/a X in, MT 1)
  8. Data In
  9. ACKnowledge line
  10. IO select 2 (optional select line driven by computer)
  11. IO select 1 (optional select line driven by computer)

Here are the Tandy options/catalogue numbers for the PC-3 series. Note that the software sold for the PC-1 was also included in ads for the PC-3, despite being exactly the same and having the same catalogue numbers, so I will not repeat them here.

Other sites on the PC-3 (note that not all acknowledge the 4K version):



[The PC-8. Click the picture for an enlarged view.]

Tandy Pocket Computer PC-8

26-3655
Introduced 1987
Originated as Sharp PC-1246
CPU: SC61720D03 (CMOS 4-bit) @ 1MHz
LCD: 16 character, non-dot-addressable
OS: S'-BASIC (18K ROM)
Base memory (free/total bytes): 1278/2048
Size: 135x70x9.5mm, 95g (0.21lb)
Options: T, P

[The PC-8 (26-3655). Click the picture for an enlarged view.]

Tandy Pocket Computer PC-8

When Tandy is determined to foul up, they just keep right on doing it. While Sharp saw fit to make a low-cost version of the PC-125x series in 1983, which started as the 8-bit PC-1245 and was then mutated down into the even more watered-down 4-bit PC-1246, Tandy didn't see fit to import it until 1987, essentially the same mistake they made with the dreadful PC-7. ['Huh??']

The shame is that the PC-1246 is judged unfairly by many unfamiliar with Sharp because of the tardiness of the PC-8, when in reality it was not at all dismal compared with its contemporaries at the time of its initial development. As a low-cost version of the PC-1250/PC-1251, it did achieve its market purpose, and it is the lightest yet easily the most durable of the Pocket Computers with its rugged hard case -- durability being a quality many Pocket Computers, even the ones Tandy didn't import, seriously lacked, and it is in fact the only Tandy Pocket Computer that does have such a rigid case. It also sported the same 11-pin I/O port, meaning it could accept PC-125x peripherals, and its BASIC was completely compatible such that anything that could tolerate the smaller screen would run without modification otherwise. Although it lacked reservable keys, something sorely missed, it did offer keyword key combinations and could still simulate reserve keys in a limited sense with the defined key function and some programming. Finally, the free memory count when compared with the PC-1250 was nearly equal.

For 1983, then, the PC-1246 was adequate, but in 1987 it was pointless. Although the MSRP was not unreasonable, at $59.95, it merely appeared as decent as it did solely when compared to the underpowered, unexpandable and low quality PC-7. While a step up from that preceding unmitigated disaster (and $10 less to boot), it was still a dismal way to finish the Tandy Pocket Computer series but incredibly was in fact outsold and outlasted by those very same ancestors. Along with the PC-5, it had one of the shortest lifetimes of any Pocket Computer, lasting less than a year.

The PC-8 is fully compatible with all PC-3 peripherals, so no special peripherals unique to it were produced, and the PC-2's large travel case was also billed as compatible.

Other sites on the PC-8:




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... Cameron Kaiser

BASIC is for lovers.