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TRS-80 Pocket Computer PC-1 with Realistic Minisette 9
Tandy PC-4 Pocket Computer
Tandy PC-6 with 8 KB memory expansion card installed and a compatible cassette interface
Tandy PC-8 Pocket Computer
TRS-80 PC-1 with a printer & cassette interface and CTR-80A cassette recorder

The Tandy Pocket Computer or TRS-80 Pocket Computer is a line of pocket computers sold by Tandy Corporation under the Tandy or Radio Shack TRS-80 brands.

Although named after the TRS-80 line of computers, they were not compatible with any TRS-80 desktop computer and did not use the Z80 CPU. Models in the Pocket Computer line were actually rebadged Sharp and Casio devices with different model names. They were given designations from PC-1 to PC-8. The PC-1, PC-2, PC-3 and PC-8 were designed by Sharp; while the PC-4, PC-5, PC-6 and PC-7 were designed by Casio.[1]

History, lineage and nomenclature

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Tandy introduced its first Pocket Computer in 1980 as an experiment; BYTE stated that "neither Tandy nor any of the other pocket-computer makers really know if there is a meaningful market for this machine". The magazine said that the vendors expected that businessmen would use them with a modem to communicate with larger computers.[2] Although not branded as such, the original TRS-80 Pocket Computer later became known as the PC-1, as subsequent models were labelled PC-2 through PC-8. Some were made by Sharp, and the rest by Casio (PC-4 through PC-7). The PC-2 had four colored ball point pens and could print or plot on plain paper. The other print-capable models all used thermal paper, the PC-3 and PC-8 used one printer, while the PC-4, PC-5 and PC-6 used another. The PC-7 had no printer or cassette interface.

Models

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The Tandy/TRS-80 model names are listed with the corresponding original Sharp or Casio model number.

Purpose

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Pocket computers were an advancement over early programmable calculator designs. In addition to providing users with scientific math functions in a small portable package, the devices also understood a form of the BASIC programming language. They included a QWERTY keyboard, of either rubber capacitive or membrane type, to use for entering the names of scientific functions and programming commands, in addition to a traditional numeric keypad. (The exception was the PC-7, which had a rectangular and alphabetically ordered keyboard, like most scientific calculators.) On some models, the alphanumeric keypad had a different type, form factor, and location than the numeric keypad.

Design

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The models provided a short one-line dot-matrix LCD display, to show the current line of input text, or a segment of it containing the cursor. Character widths in these models varied from 12 characters in the PC-4 and PC-7 to 24 characters on most of the rest. The displays also included some way of indicating operational mode, scientific mode, and other states and conditions.

The Casio models included lower-case characters. These were only for use in PRINT statements, as lower-case commands and variables were not accepted as with almost all BASIC programming machines.

In general, the two specific lines were not cross-compatible, but there were compatibilities within lines. PC-1 programs would work unmodified on the PC-3 and on the PC-8 with changes for screen size, and PC-4 (26-3650B) programs would run unmodified on the PC-5, PC-6 and PC-7. The PC-2 was a unique architecture and was the only unit in the line allowing direct memory access with POKE, PEEK and CALL.

Operating modes

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Each model had two operating modes: Run and Prog.

Run

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In Run mode, the command line could be openly used to execute one-line, non-BASIC operations. This is the normal mode used, from where arbitrary calculations could be entered to receive results. The Run mode also allowed the execution of the BASIC programs stored in the device.

Instead of an "equals" key to initiate calculation evaluation, an "EXE" (execute) key was provided. This caused confusion with those who were used to traditional calculators. The = character was used only for variable assignment, and evaluation tests in programs.

The input of simple calculations would be aggregated on the command line, and no results would be displayed until the EXE key was pressed. In some models, a special ANS variable was provided to reuse the results of the previous calculation; in others, the previous calculation was automatically included if the next calculation began with an operator.

Some valid calculation input examples (PC-8): 

 SIN40
 10+2+(8*1)/7
 TAN (LOG (√(4/3)))

Prog

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The Prog mode changed the input from a command line to a program editor. In this mode, BASIC programs could be entered one line at a time. Up and down arrow buttons were provided to scroll up and down through the program space. On most models, free calculations could not be entered in the Prog mode. Certain models, especially the Casio-derived ones, called this mode WRiTe mode.

On the Sharp models, there was only one line numbering space. In order for multiple programs to exist on the device, they had to be written in different ranges of line numbers. For example, it was common to insert one program starting with line 100, and another program starting at line 200, etc. Valid line numbers in most models were from 1 to 999. To prevent run-on execution, each program had to finish with the END command, unless run-on execution was desired. On Sharp-derived units, labels could be inserted into the program, usually single characters such that in Run mode, that program could be executed by depressing a special DEF key followed by the key of that character. This was equivalent to an explicit GOTO command to the first line number of that section of program, which was also a valid way to execute programs from Run mode.

In the Casio-derived models, the BASIC space was subdivided into segmented program spaces which could be numbered, cleared and executed manually, or could call each other.

Many of the devices included a special modifier key to expedite the entry of BASIC commands as well as scientific function names. The most common commands would each be associated with a key, and the full command could be entered by depressing the special modifier key, followed by the associated key for the command.

In some models, BASIC and other commands would be converted into one-character tokens (converted to strings upon display) instead of being stored as whole strings.

Memory

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The total memory capacity of the devices varied from 1 KB to 12 KB and up as far as 16 KB with the use of an available RAM card (only for some models). The optional RAM cards varied in sizes from 1 KB, 4 KB and 8 KB.

All user storage was taken from the same space, so allocation of arrays using DIM would decrease the available memory for program instructions, and vice versa. However, the storage space for one-character alphabetical variables was pre-allocated, and as a result the A array had special significance in many units. For example, in the PC-8, the A array actually pointed to the locations of the alphabetical variables, so A(2) pointed to the value of B, and so on. As a result, published programs for the device avoided the use of A as either an array or an alphabetical variable. On some models the entire variable space could be manipulated in this fashion.

Other notes

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Undocumented commands

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The PC-3 and PC-8 had a couple of commands that were not listed in the manual, but nonetheless were recognized by BASIC and usable.

  • CALL {memory location}; PEEK {memory location} and POKE {memory location},{byte value} - the highest memory location is 2047, and it is possible to modify the BASIC program in RAM directly with POKE, as well as access a certain memory location (37, possibly?) that controls the DEG/RAD/GRAD spots on the LCD. With judicious POKEs into the BASIC program text area more characters in the PC-8 character set can be discovered, including a `tilde` which also seems to function as a bizarre command. Some blank characters when PRINT#'ed will display additional symbols on the printer if one is attached.
  • CK00 - seems to be some type of test mode for the display. Will show a couple of patterns on the LCD and then appear to lock up.
  • CK01 - seems to be some type of test mode related to the optional Printer Interface

Also, SHIFT-6 on the PC-8 will display a Yen symbol.

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Tandy Pocket Computer

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from Grokipedia
The Tandy Pocket Computer (also known as the Pocket Computer) was a line of portable, handheld computers introduced by through its retail chain, beginning in 1980, and consisting of rebranded models from manufacturers Sharp and that featured built-in capabilities for on-the-go computation, data management, and simple applications. These devices, sized similarly to advanced calculators, represented an early form of personal digital assistants (PDAs) and were notable for their compact design, LCD displays, and expandability via optional peripherals like cassette interfaces and printers, targeting hobbyists, professionals, and students for tasks such as scientific calculations, program storage, and basic data processing. The series debuted with the PC-1 model in July 1980, a rebadged Sharp PC-1211 with 1.9 KB of RAM, an 11 KB ROM containing a , a 24-character LCD display, and a 57-key keyboard, initially priced at $249.95 and powered by four PX675 mercury batteries (or equivalents like LR44) for up to 300 hours of use. Subsequent models evolved in features and performance: the PC-2 (), based on the Sharp PC-1500, introduced an 8-bit processor, up to 16 KB expandable RAM, and a ; the PC-3 (1983), from the Sharp PC-1250, added capabilities; the PC-4 (1983), a PB-100 rebrand with 544 bytes of RAM, gained cultural fame through its appearance in the film ; while later entries like the PC-5 (1985, FX-780P, 4 KB RAM), PC-6 (1986, FX-790P, up to 8 KB RAM), PC-7 (1988, -based), and PC-8 (1987, Sharp-based) offered improved keyboards and features, with the line continuing until the late 1980s. These pocket computers operated in distinct modes—such as RUN for execution and PRO for programming—and supported fixed or flexible memory allocation for variables and programs, though they were incompatible with Tandy's larger desktop systems due to differing architectures. Despite their innovative portability, the Tandy Pocket Computers faced limitations like small capacities, lack of lowercase text support in early models, and from graphing calculators and emerging laptops, leading to declining sales by the late 1980s as Tandy shifted focus to other product lines. Nonetheless, they played a key role in popularizing programmable handhelds, influencing the development of modern smartphones and tablets by demonstrating the viability of pocket-sized computing for everyday use.

History and Lineage

Origins and Development

In the late 1970s, , operating through its retail chain, recognized the explosive growth in personal computing following the success of its desktop microcomputers introduced in 1977. To extend this momentum into portable devices, Tandy aimed to provide compact, battery-powered alternatives that could appeal to consumers seeking on-the-go computing amid the rising popularity of microcomputers for home, education, and business use. Beginning in 1980, Tandy established partnerships with Japanese manufacturers Sharp and to rebrand their advanced programmable calculators as the Tandy Pocket Computer line, targeting the U.S. market with affordable, accessible handheld devices. These collaborations enabled Tandy to leverage established Japanese expertise in and , bypassing the need for in-house hardware development while aligning with RadioShack's strategy of offering entry-level technology to a broad audience. Sharp provided the foundational models, with Casio contributing later iterations for cost-effective expansion. The line debuted with the PC-1 in 1980, a rebranded Sharp PC-1211 that transitioned devices from simple functions to fully programmable handhelds using , complete with a keyboard and LCD display for running user-defined programs. Priced at around $250, the PC-1 democratized portable programming, allowing tasks like and calculations in a device small enough to fit in a , and it quickly became a through stores. Across the series, processor technology advanced from 4-bit chips in the PC-1, operating at modest clock speeds for basic operations, to more capable 8-bit architectures in subsequent models like the PC-2 (based on Sharp's LH-5801). This evolution, fueled by rapid innovations in Japanese electronics during the early , enhanced performance for complex programs and multitasking, keeping the Tandy line competitive in the emerging portable computing landscape.

Timeline and Production End

The Tandy Pocket Computer line began with the release of the PC-1 in 1980, marking 's entry into portable computing through its retail network. This model, a rebranded Sharp PC-1211, set the foundation for subsequent iterations focused on programmable functionality in a compact form. The lineup expanded rapidly in the early 1980s, with the PC-2 launching in 1982 as an advanced model based on the Sharp PC-1500, featuring expanded and capabilities. In 1983, Tandy introduced both the PC-3 (a budget-oriented Sharp PC-1250 with 2K RAM) and the PC-4 (a PB-100 rebrand priced under $100), broadening accessibility for basic programming and calculation tasks. The mid-1980s saw further diversification, including an upgrade to the PC-3A in 1984 with 4K RAM. That same year, Tandy shifted branding from the prefix to simply "Tandy," aligning the pocket computers with its evolving broader lineup of personal computing products beyond the original desktop systems. The PC-5 arrived in late 1985 as a FX-780P rebrand, followed by the PC-6 in 1986 and the PC-7 in 1987, both Casio-derived models emphasizing scientific computing with improved RAM and battery life. The series concluded with the PC-8 in 1987, a short-lived Sharp PC-1246 variant aimed at low-cost entry-level use. The pocket computers reached peak popularity in the mid-1980s, benefiting from widespread distribution through RadioShack's extensive store network of over 7,000 locations across the , which facilitated hands-on demonstrations and software sales. This era aligned with growing interest in portable electronics for , , and fieldwork, positioning the devices as affordable alternatives to full-sized computers. However, by the late 1980s, sales declined amid intensifying competition from more powerful computers like the PC compatibles and Tandy's own shifting priorities toward desktop and portable PCs such as the series. Production of the Tandy Pocket Computer line effectively ended around 1991, with the durable PC-6 remaining in catalogs until that year despite the introduction of newer models. This closure reflected the broader obsolescence of dedicated pocket computers, as emerging personal digital assistants (PDAs) and advanced laptops offered superior integration of computing, communication, and features.

Models and Specifications

Early Models (PC-1 to PC-3)

The Tandy Pocket Computer PC-1, introduced in and based on the Sharp PC-1211, marked the entry into Tandy's line of portable programmable devices. It featured a dual 4-bit CPU configuration using SC43177 and SC43178 processors operating at 256 kHz, providing 1.9K of total RAM with 1.4K available for user programs and data. The system included 11K of ROM containing the S'-BASIC interpreter, a 24-character dot-matrix LCD display for text output, and a cassette interface for and transfer via optional adapters like the CE-121. Initially priced at $249.95, the PC-1's compact design—measuring approximately 7 x 2.75 x 0.7 inches and weighing 6 ounces—emphasized portability while enabling basic scientific calculations and simple programming tasks. The PC-2, released in 1982 and derived from the Sharp PC-1500, represented a significant advancement with an 8-bit LH-5801 CPU running at 1.3 MHz, offering improved performance over the PC-1's architecture. It provided 1.85K of user RAM, expandable up to 16K through plug-in modules, alongside 16K of ROM for an extended BASIC dialect that supported graphics commands. Key innovations included a 26-character LCD with 156 x 7 resolution for bitmapped capabilities, a built-in for time-sensitive applications, and interfaces such as for and cassette ports for storage. Priced at $279.95 upon launch (later reduced to $199.95), the PC-2's larger form factor—about 7.7 x 3.4 x 1 inch and 13 ounces—accommodated a 65-key keyboard, making it suitable for more complex programs involving plotting and data visualization. Introduced in 1983, the PC-3 was based on the Sharp PC-1250 and addressed some limitations of earlier models with an 8-bit SC61860 CPU at 576 kHz, 24K of ROM, and 1.4K of user RAM (from a total of 2K). It retained a 24-character LCD display similar to the PC-1 but offered enhanced efficiency and full compatibility with PC-1 software and peripherals. The 1984 PC-3A upgrade, aligned with the Sharp PC-1251, increased user RAM to 4K total, providing more space for larger programs without altering the core design or display. Both models, priced at $99.95, featured a slimmer profile—around 5.3 x 2.75 x 0.4 inches and 4 ounces—and maintained cassette and printer interfaces, solidifying while improving overall usability. These early models established the foundational role of the Tandy Pocket Computer series by progressively introducing in the PC-2 for visual applications and RAM expansions in the PC-3A to mitigate memory constraints in portable computing. The shift from 4-bit to 8-bit processing across the lineup enhanced execution speed and program complexity, paving the way for broader adoption in educational and professional settings.
ModelYearBase Sharp ModelCPUUser RAM (Total)ROMDisplayKey InterfacesInitial Price
PC-11980PC-1211Dual 4-bit @ 256 kHz1.4K (1.9K)11K24-char LCDCassette$249.95
PC-21982PC-15008-bit @ 1.3 MHz1.85K (expandable to 16K)16K26-char, 156x7 LCD, Cassette$279.95
PC-31983PC-12508-bit @ 576 kHz1.4K (2K)24K24-char LCDCassette, Printer$99.95
PC-3A1984PC-12518-bit @ 576 kHz4K24K24-char LCDCassette, Printer$99.95

Later Models (PC-4 to PC-8)

The later models of the Tandy Pocket Computer, produced from 1983 to 1987, represented a shift toward cost-effective designs sourced primarily from , prioritizing affordability and compactness over the expandability seen in earlier iterations. These devices targeted budget-conscious users such as students and hobbyists, with prices often under $100, reflecting Tandy's strategy to extend the line's market viability amid declining interest in pocket computing. While maintaining capabilities, the models emphasized portability, with thinner profiles and simplified interfaces, though some suffered from reliability issues due to cost-cutting measures. The PC-4, introduced in 1983 and based on the PB-100, offered 544 bytes of user RAM powered by a 4-bit CPU, a 12-character LCD display, and segmented program memory that functioned as an early form of filesystem for organizing code in blocks labeled P0 through P9. Lacking built-in expansion options, it focused on basic standalone operation without peripherals, positioning it as an entry-level device priced around $50 to appeal to casual programmers. In 1985, the PC-5 arrived, derived from the FX-780P, with 4K of RAM, a 24-character LCD, and a split keyboard design that allowed for a more compact folded form factor. However, its construction quality was compromised by cost reductions, leading to a relatively short commercial lifespan marked by frequent hardware failures. The PC-6, released in 1986 and also based on a design, improved on its predecessor with 8K of base RAM expandable to 16K via an integrated , a 24-character LCD, and a two-tone for enhanced . This model supported limited peripherals through its expansion capabilities and remained in sales through 1991, outlasting other later variants due to its balanced feature set. That same year, the PC-7 emerged as a low-end option based on the FX-5200P, providing under 1K of user RAM and no expansion ports, intended as a direct successor to the PC-4 but criticized for underwhelming performance relative to its positioning. Its 12-character display and basic functionality underscored Tandy's emphasis on , though it failed to capture significant market traction. The line concluded with the 1987 PC-8, adapted from the Sharp PC-1246, featuring 1.3K of user RAM, a compact 16-character screen, and compatibility with PC-3 peripherals via an 11-pin interface, offering only incremental refinements as the final entry. Priced at $59.95, it highlighted the series' endgame focus on legacy support rather than innovation. Overall, these models marked Tandy's pivot to partnerships for cheaper manufacturing, resulting in sleeker, more portable units that traded power and modularity for accessibility, though this approach contributed to the line's gradual phase-out by the late 1980s.

Design and Hardware

Physical Design and Input

The Tandy Pocket Computer series emphasized compact, calculator-like form factors designed for easy portability, typically measuring around 6 to 8 inches in length, 2.5 to 3.5 inches in width, and less than 1 inch in thickness, with weights ranging from 4 to 16 ounces depending on the model. For instance, the early PC-1 measured 6 7/8 by 2 3/4 by 11/16 inches and weighed 6 ounces, while the PC-2 was larger at approximately 195 × 86 × 25 mm (7.7 × 3.4 × 1.0 in) and 375 g (13.2 oz) with batteries. Later models like the PC-4 shrank to approximately 6.5 by 2.8 by 0.4 inches and 4 ounces, and folding designs such as the PC-5 measured 5.6 by 2.8 by 0.7 inches when closed. These dimensions allowed the devices to fit in a or pants , aligning with their name and marketing as on-the-go computing tools, though protective slip-on covers were sold separately to guard against scratches and drops during carry. Power systems evolved from larger battery setups in early models to more compact cells in later ones, prioritizing longevity and portability. The PC-1 and similar early units ran on four PX675 mercury cells, providing up to 300 hours of operation, while the PC-2 used four AA alkaline batteries for about 75 hours. By the PC-3 and subsequent models like the PC-4, PC-6, and PC-7, power shifted to two CR2032 cells, offering low consumption around 0.02 watts maximum and extended runtime, often with a secondary for memory retention in units like the PC-5 and PC-6. Across the line, power s and mode switches—typically including on/off, run, and text modes—were standardized in placement on the side or top edge for quick access, with low-battery indicators common to prevent data loss. Input methods varied to balance compactness with usability, featuring full keyboards on larger early models and more abbreviated designs on slimmer later ones. The PC-1, PC-2, and PC-3 incorporated 52- to 65-key layouts in miniature form, enabling efficient typing for programming and text entry despite reduced key sizes. In contrast, smaller models like the PC-4 and PC-7 used numeric keypads with alphabetic overlays accessed via shift keys, limiting direct letter input but suiting calculator-style operation. The PC-5 introduced a split folding keyboard with a mushy section on top and firmer keys below, though its hinges and latches proved prone to failure over time. Build quality differed notably between eras, with early models boasting durable plastic cases that withstood regular use, as seen in the robust of the PC-1 and PC-2. Later units like the PC-5 and PC-7 suffered from flimsier materials, including flexible cases that distorted under strain and fragile folding mechanisms, leading to common issues like hinge splits and poor long-term durability compared to their predecessors. Despite these variations, the series maintained a consistent emphasis on lightweight, ergonomic designs for mobile professionals and hobbyists.

Display and Processor

The Tandy Pocket Computer series featured monochrome LCD displays optimized for portability and low power consumption, with variations across models reflecting advancements in resolution and functionality. Early models like the PC-1, PC-2, PC-3, PC-5, and PC-6 utilized a 24-character dot-matrix LCD, typically with a resolution of 156x8 pixels, enabling clear text rendering in a single line. In contrast, the PC-4 employed a simpler 12-character non-dot-addressable LCD for basic text output, while the PC-8 had a more compact 16-character dot-matrix display with 96x8 pixels to suit its smaller form factor. Processor architecture evolved from basic 4-bit designs to more capable 8-bit units, enhancing computational efficiency without sacrificing battery life. The PC-1 relied on dual 4-bit processors (SC43177/SC43178) at 256 kHz, while the PC-4 used a single 4-bit HD61913A01 at 200 kHz—suited for fundamental arithmetic and operations. Subsequent models shifted to 8-bit processors for improved performance: the PC-2 used an LH5801 at 1.3 MHz, the PC-3 an SC61860 at 576 kHz, and the PC-8 a 4-bit SC61720D03 at 576 kHz; the PC-5 and PC-6 featured HD61747-series processors at approximately 0.5 MHz. These designs prioritized low-power operation, often drawing from VLSI integration to minimize energy use in handheld environments. Graphics capabilities were limited but innovative in select models, with all units supporting text for multi-line program review, though none included color. The PC-2 stood out with its unique -based mode, utilizing a 156x7 resolution for simple plots and custom characters via commands like GCURSOR and GPRINT, enabling rudimentary visualizations such as line graphs. Later models like the PC-5 and PC-6 lacked dedicated screens, focusing instead on text-only output despite their dot-matrix displays. Starting with the PC-2, a was integrated for time-sensitive applications, further optimizing efficiency by allowing precise timing without external dependencies.

Software and Operation

Operating Modes

The Tandy Pocket Computer series employed a dual-mode operating system to balance immediate computational tasks with program development, a design choice that distinguished it from single-purpose calculators of the era. This interface separated routine operations from , allowing users to toggle between modes efficiently for targeted workflows. RUN mode served as the default entry point upon powering on, optimized for quick arithmetic and scientific calculations without the overhead of program structures. Users could input expressions directly on the command line for immediate , leveraging 16 built-in functions including trigonometric operations (such as , COS, and TAN), logarithms, , and , alongside basic arithmetic and statistical tools like square roots and factorials. This mode also facilitated program execution by entering the RUN command followed by a or program label, as well as viewing and manipulating variables (A-Z for numerics, strings up to model-dependent limits). Outputs appeared directly on the display, supporting one-line non-stored computations akin to a , with results retained in the ANS register for further use. To enter PROG mode, users activated a physical slide switch on early models such as the PC-1, PC-3, and PC-8, which toggled directly between RUN and PROG, or pressed a key sequence like the MODE key (cycled until "PRO" displayed) on models like the PC-2. In PROG mode, the focus shifted to program management, where users entered statements prefixed with line numbers ranging from 1 to 65279 to ensure sequential storage and execution. Editing involved inserting, deleting, or modifying lines using cursor controls, with the system providing error handling for syntax violations (e.g., "") and runtime issues during testing. Programs could be listed for review, saved to optional peripherals, and executed upon returning to RUN mode, emphasizing a development cycle separate from ad-hoc calculations. Line numbering enforced ordered code structure, preventing free-form entry and aiding in through traceable jumps and loops. Mode transitions were straightforward but rigid, with the physical switch or key combo restoring to its primary state for in RUN or focused development in PROG, reflecting the era's hardware constraints. The absence of multitasking meant only one mode operated at a time, requiring deliberate switches that cleared the command buffer to avoid conflicts, though persistent variables and programs remained intact across changes unless explicitly cleared. This setup prioritized simplicity and resource efficiency in a compact form factor, making the Tandy Pocket Computer versatile for both professional calculations and hobbyist programming. Note that dialects are model-specific and generally incompatible between Sharp-based (PC-1,3,8) and Casio-based (PC-4-7) models.

Programming Language and Commands

The Tandy Pocket Computers primarily used dialects of BASIC optimized for portability and limited resources. The PC-1 featured S'-BASIC, a compact, single-byte tokenizing variant akin to TRS-80 Level I BASIC, supporting floating-point arithmetic with 10-digit precision and limited to 26 single-letter variables (A-Z). Later models like the PC-2 introduced Extended Pocket BASIC (also known as S-BASIC), which expanded capabilities to include string handling with functions such as LEFT,RIGHT, RIGHT, LEN, and MID$, as well as graphics commands for the built-in plotter, including PLOT and LINE to draw points and connect them on 2.25-inch paper. The PC-3 employed an expanded BASIC dialect with statement compaction, supporting variable-length strings up to 80 characters for simple variables and enhanced array handling, while the PC-8 used S'-BASIC compatible with the PC-3, with a limited command set for scientific applications. Core programming commands were consistent across models, drawing from standard syntax to facilitate program control and data manipulation. Essential statements included PRINT for displaying results or prompts, INPUT for reading user values, and GOSUB for branching and subroutine calls, IF-THEN for conditional execution, and FOR-NEXT loops for iteration, enabling straightforward algorithmic structures like calculations and decision trees. Programs were line-based, requiring numbered lines (typically 1 to 254 on the PC-1, extending to 999 on models like the PC-3), with a maximum of one statement per line and execution starting from the lowest upon RUN. In the PROG mode (briefly referenced in operating contexts), these commands formed the basis for entering and editing code directly. Built-in functions supported a range of computations, prioritizing within hardware constraints. Scientific functions such as , COS, TAN, LOG, EXP, and were available on models from the PC-2 onward, allowing trigonometric and logarithmic operations essential for tasks. String functions like ASC, CHR,STR, STR, and VAL facilitated text processing in extended dialects. Advanced models incorporated functions including for direct hardware register access, enabling low-level operations like memory inspection. Error handling relied on descriptive codes to diagnose issues during execution or editing. Common errors included "" for invalid command formats, "MEMORY FULL" when program steps exceeded available RAM, and numbered codes on later models like the PC-3 (e.g., 1 for syntax issues, 6 for overflow, 8 for I/O problems with peripherals). These messages, displayed on the LCD, guided users to correct input or resource limitations without advanced tools.

Memory and Expansion

Memory Architecture

The memory architecture of the Tandy Pocket Computer series utilized a fixed (ROM) section for the and operating system, typically ranging from 10 KB to 24 KB across the series, which remained immutable and dedicated to system functions. User-accessible (RAM) was volatile and shared among program storage, variables, and the execution stack, with no support for or paging mechanisms. This design prioritized compactness but imposed strict limits on application size and complexity, often leading to "MEMORY FULL" errors during program compilation or runtime when allocations exceeded available space. In the initial models, such as the PC-1, total RAM totaled 1.9 KB, of which approximately 1.4 KB was allocated for user programs (up to 1,424 steps) and a fixed set of 26 variables (A-Z), with the remainder reserved for the stack and system buffers, including a display buffer of around 300 bytes for the 24-character LCD. Variables were pre-allocated upon initialization, consuming a predictable portion of RAM regardless of usage, which encouraged efficient coding to maximize program space; flexible allowed unused variable space to be repurposed for additional program steps in some configurations. Later early models like the PC-3 had 2 KB total RAM (~1.4 KB available) in its initial 1983 version (equivalent to Sharp PC-1250), expanding to 4 KB total (~3.5 KB available) in the 1984 PC-3A variant (equivalent to Sharp PC-1251), maintaining the distinction between fixed system areas and dynamic user allocation. Subsequent models introduced greater flexibility and capacity, exemplified by the PC-6 with 8 KB base RAM (yielding roughly 7.5 KB user-available after system overhead), where was dynamically divided among programs, variables, and stack without fixed pre-allocation for all variables, allowing more efficient use for larger applications. The PC-4, however, employed a segmented approach in its 4-bit , with base RAM of 1 KB (544 bytes available, expandable to 2 KB total with ~1.6 KB available using a 1 KB upgrade) supporting multiple small, independent programs rather than a single monolithic one, mitigating limitations through modularity. Across the line, RAM lacked built-in persistence, relying on external cassette saves for , as power loss erased all user content. Expansion options, such as additional RAM modules for the PC-6, could increase capacity but were addressed through peripheral interfaces.

Interfaces and Accessories

The Tandy Pocket Computer series featured a range of interfaces designed for , output, and connectivity, primarily through expansion ports. Early models like the PC-1, PC-2, and PC-3 included cassette ports via dedicated interfaces for saving and loading programs and . The PC-1 used a Printer/Cassette Interface (catalog number 26-3503) that connected to standard cassette recorders like the Minisette-9, enabling program storage at typical cassette speeds of the era. Similarly, the PC-2's Printer//Dual Cassette Interface (26-3605) supported dual-cassette operation for reliable transfer, while the PC-3 relied on a combined Printer/Cassette Interface (26-3591) for the same purpose. These cassette systems allowed users to archive programs and externally, extending the limited internal memory. Serial connectivity was available on select models through RS-232 interfaces, facilitating integration with printers, modems, and other devices. The PC-2 offered an RS-232C Interface (26-3612) supporting baud rates from 50 to 2400, which enabled terminal emulation and communication with online services or external peripherals. The PC-8 also supported RS-232 functionality, compatible with modems and serial printers, building on the design of its Sharp PC-1246 counterpart. Expansion options enhanced the core functionality of several models, particularly through modular add-ons. RAM cards were available for the PC-2, supporting up to 16K total via 4K (26-3615) or 8K (26-3616) modules that plugged into the rear expansion slot, allowing for larger programs and data handling. The PC-6 similarly expanded to 16K with an 8K RAM module, while the PC-4 could reach 2 KB total using a 1K upgrade. Printer modules provided output capabilities, with the PC-1 and PC-3 using dot-matrix interfaces for 16-24 characters per line, and the PC-2's supporting four-color graphics on 256x4096 resolution paper. A variety of accessories supported portability and power needs across the lineup. Protective cases were offered for most models, including a padded vinyl carrying case (26-3608) for the PC-2 that accommodated the printer interface and , and simpler travel cases (26-3654) for the PC-4, PC-6, and PC-8. and chargers were standard inclusions or optional add-ons, such as the one for the PC-2's interface, ensuring reliable operation beyond battery life. Cassette recorders, like the CTR-80A, paired with the interfaces for external storage, and the PC-4's dedicated external cassette module (26-3651) was notably featured in promotional materials and media demonstrations of the era. Compatibility among models relied on proprietary cables and connectors, limiting interoperability with non-Tandy devices but enabling shared peripherals within the line. Early models like the PC-1 used unique 60-pin or DIN-style cables for their interfaces, while later Casio-based units (PC-4 to PC-6) required specific link cables (26-3671) to adapt PC-4 peripherals. The PC-3 and PC-8 shared full compatibility for printer/cassette modules, allowing upgrades without new hardware. This design prioritized seamless expansion within the Tandy ecosystem but often necessitated official accessories for optimal performance.

Advanced Features and Legacy

Undocumented Capabilities

The Tandy TRS-80 PC-2 supported direct entry of code through its Extended Pocket interpreter, utilizing commands to access hardware registers and locations for low-level programming. This capability allowed users to write custom routines, such as advanced manipulation on the dot-addressable 26-character LCD display, by directly manipulating display bytes— for instance, POKEing values to specific addresses to draw lines or shapes beyond the standard commands such as GCURSOR and POINT. Unlike other models in the line, the PC-2's LH-5801 processor and open architecture enabled seamless integration of within programs via CALL statements, facilitating efficient hardware access like interrupt handling or custom I/O operations. The PC-4's segmented memory system featured ten program slots (P0-P9) that divided the available RAM (base 544 bytes, expandable to about 1.5 KB with options), which power users exploited as a rudimentary filesystem for application swapping without full reloading from tape. By using the CALL slot_number , programs in one slot could invoke or chain to routines in others, enabling modular organization and data sharing across slots—effectively simulating a multi-app environment on the limited RAM. This feature, utilized by enthusiasts in the late and early , allowed efficient storage of utility libraries or levels, though it required careful management to avoid slot conflicts during execution. Hidden commands in the PC-2 included direct access to the internal via PEEK at specific undocumented addresses, such as those mapping the clock's registers, permitting precise timestamping or alarm functions outside the standard TIME statement. These features, uncovered by hobbyist reverse-engineering in online forums and newsletters after the devices' discontinuation, extended the units' utility for timing-sensitive applications. Exploiting these capabilities carried risks, including from invalid memory writes or battery removal without , which could render the unit unresponsive on these battery-powered systems with no built-in recovery mechanisms.

Cultural Impact and Preservation

The Tandy Pocket Computer line gained notable visibility in popular media during the , particularly through its appearance in the 1984 film , where the PC-4 model, rebadged from the PB-100, was used by the character for logging ghost data via a cassette interface attachment. This depiction highlighted the device's portability and utility in fieldwork, contributing to its cultural recognition as an early example of compact computing technology in cinema. The series had a significant market impact by democratizing access to personal programming for hobbyists and students, with models like the PC-4 priced affordably at around $59.95, making accessible without requiring a full-sized computer. Sold exclusively through stores, the pocket computers drove substantial sales in the early , with U.S. pocket computer revenues reaching $150 million in 1983 alone, influencing a generation of early coders and sparking interest in portable electronics. Preservation efforts have sustained the legacy of the Tandy Pocket Computers, with emulators like PockEmul enabling modern recreation of compatible vintage pocket computers on smartphones and desktops, including support for later Sharp models akin to the Tandy line. Online archives, such as Floodgap Retrobits, maintain detailed documentation, including scanned manuals and technical overviews for PC-1 to PC-6, actively soliciting donations of hardware and peripherals to prevent loss as of 2024. In contemporary retro computing communities, the Tandy line continues to attract collectors seeking functional units for nostalgia and experimentation, as evidenced by active trading on platforms like and discussions in enthusiast forums. Recent events, such as the Tandy Assembly conferences in 2024 and 2025, have featured talks on programming and preserving Tandy Pocket Computers, fostering appreciation for their role in the evolution of portable computing. While no official revivals have occurred, the devices inspire ongoing projects in vintage hardware restoration and emulation.

References

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