Commodore Plus / 4

Commodore Plus / 4

Manufacturer

Commodore International

Main developer

Bil Herd (management, hardware), Dave DiOrio (TED, hardware), Ira Velinsky (housing), Terry Ryan (operating system, BASIC 3.5), David Johnson (3-plus-1 application software)

Sales start and new price

Fall 1984 for US $ 299 Fall 1984 for £ 249 in early 1985 for DM 1,300 in early 1985 for around ₤ 1,000,000

Cessation of production

1985

Devices sold

827,000

Main processor

MOS 7501 or 8501 @ 1.77 MHz (PAL)

RAM ex works

64 KB DRAM

Graphics output

40 × 25 characters 320 × 200 pixels, 160 × 200 pixels maximum 121 colors

Sound output

2 tone generators, one of which is optionally 1 noise generator

Housing dimensions (H / W / D)

67 mm / 338 mm / 203 mm

scope of delivery

Computer, power supply, antenna cable, user manual, 3-plus-1 software manual, warranty card, Commodore extra guarantee, interference suppression certificate, cardboard packaging, Styrofoam upper and lower shell

The Commodore Plus / 4 is a home computer based on the 7501 or 8501 microprocessor from the US manufacturer Commodore International .

The device was designed from mid-1983 under the name Commodore 264 as an inexpensive addition to the successful home computers Commodore VC 20 and Commodore 64 . In addition, the Sinclair ZX Spectrum was primarily intended to take market share with the new model . The technical and design data of the computer had to be subordinate to the maximum manufacturing costs of 50 US dollars specified by the company management. As a result, the number of electronic circuits was significantly reduced with the help of the special TED component and a smaller housing was designed, but without maintaining downward compatibility with the Commodore VC 20 and 64. While developing the TED, Commodore decided to realign the product towards an application-oriented device for smaller offices. The associated upgrade to 64 kilobytes (KB) of RAM and the implementation of the permanently installed application software 3-plus-1 ultimately led to the computer being renamed Commodore Plus / 4 , in addition to making it considerably more expensive .

The device, initially only shipped in North America from the fall of 1984, was advertised as a “Productivity Computer” (home user computer) and sold for 299 US dollars. Shortly afterwards, other sales markets such as Europe were added. Due to the poor sales, some drastic price reductions quickly followed, which resulted in the complete sale by Commodore after Christmas 1985. The computer gained fame in West Germany mainly through the computer learning course , a package consisting of the Commodore Plus / 4, a data recorder and additional beginner 's literature , which Aldi sold on sale from 1986 onwards .

Due to the low hardware and software compatibility to the previous models, the lack of graphics capabilities for games ( sprites ) and only limited sound generation, the Commodore Plus / 4 was not a great commercial success despite otherwise good technical indicators and powerful peripheral devices . In contrast to the Commodore 64, the Commodore Plus / 4 only made a small contribution to the original goal of wresting market leadership from Sinclair with only around 830,000 units sold worldwide. Production - including the technically dismantled entry-level versions Commodore 16 and Commodore 116 - was discontinued after gradual throttling as early as 1985, as the sales of the older, but better supported, Commodore 64 reached unexpected heights. In addition, with the company's own models such as the Commodore 128 and the Amiga 1000 , but also the ST series of the direct competitor Atari, significantly more powerful successors were now available.

history

During the booming home computer era in 1983, Commodore's inexpensive entry-level model VC 20 from 1981 was already out of date and the successful Commodore 64 launched at the end of 1982 only served the higher price segment. In 1983, the company management initiated the construction of a new computer to develop the previously inaccessible, prosperous low-price area around the Sinclair Spectrum .

Development and prototypes

The planned new product based on the tried and tested 8-bit architecture had to manage with a minimum of electronics following the instructions of the company management. This should enable production costs to be reduced to $ 50 on the one hand and the use of a smaller housing on the other - important key figures for being able to compete with a target sales price of $ 100, especially with regard to the inexpensive and compact Sinclair Spectrum.

The TED project

The engineers from MOS Technology and Commodore commissioned with the development initially turned to the construction of a new special electronic component. This should combine all functions for the generation of graphics and sound as well as input and output operations and enable savings in production costs as well as housing space. The corresponding functional groups of the later MOS 7360 called the integrated circuit (chip) were thereby developed from scratch.

MOS Technology logo

The properties of the special modules for graphics and sound generation built into the Commodore 64 and VC 20 were not included in the specifications during construction. On the one hand, its developers and the required knowledge had already left Commodore and, on the other hand, the marketing department had meanwhile changed the potential area of ​​application for the new system after Commodore had steadily lost market shares in the field of high-quality office computers. The previously untapped segment of professional home users - smaller offices and craftsmen - now came into focus. Accordingly, the capabilities of the system to be developed should be aligned to these new requirements. This primarily concerned the use of utility programs such as word processing , spreadsheets , databases and the versatile display of the results generated. The new main task of text-oriented use is also reflected in the naming of the chip as a text editing device or in the acronymized short form TED .

Microprocessor MOS 8501, successor to MOS 7501 in new manufacturing technology

The resulting good graphics capabilities of the MOS 7360 were paired with an optimized 6502 microprocessor, the MOS 7501 . New types of components also for the main memory in the form of 16 KB DRAM chips helped to further reduce the number of components and the built-in programming language BASIC , which was to be expanded, promised uncomplicated use of this new high-performance hardware. This computer system, specially tailored to the new MOS 7360 and 7501, was henceforth listed as a TED project in the development documents. First information, probably brought into circulation by Commodore himself in the sense of better marketing at relevant computer fairs, spoke either of the Ted computer or the code name 444 .

The Commodore 264 models

From the summer of 1983, the Commodore marketing department expanded the development program of the TED computer to include various expansion stages with special "features". Three different configurations quickly emerged, to which special attention was paid: At the lower end of the model range, the Commodore 116, equipped with an eraser keyboard and 16 KB RAM, ranked as the originally planned "Sinclair Killer". The more ambitious Commodore 264 model for semi-professional use was placed in the middle area. The concept provided for 64 KB of RAM, a full-fledged typewriter keyboard and a built-in package of utility programs based on Lotus 1-2-3 - a novelty in microcomputer history. The plan was to leave the selection of the individual application programs to the potential buyer, who should be able to put together his tailor-made program collection in a simple manner. The premium model with the designation Commodore 364 supplemented the Commodore 264 with a built-in speech synthesis module , an enlarged housing with numeric keypad and corresponding software.

Prototype of the Commodore 264 model series

In terms of a comfortable operation of the high-quality models Commodore 264 and 364 began to be integrated software package it with a Commodore to Macintosh computers from Apple -inspired windowing equip operating system. In addition, those responsible specified that the intended applications such as spreadsheets, word processing, database, programming languages and graphics programs should be optimally coordinated, for example to ensure easy interchangeability of the data. The user should be able to process tasks that go beyond this by means of self-created programs. For this purpose, an extension of the Commodore Basic 2.0 was planned for the uncomplicated creation of commercially oriented software and for using the high-resolution color graphics of the TED. All work on the implementation of the software began after the company headquarters had moved in late summer 1983.

The prototypes of the Commodore 264 models and the Commodore 364 including a newly developed 5¼-inch floppy disk drive SFS 481 were presented to a wider public for the first time at the Winter CES trade fair in Las Vegas in January 1984. As a result of a change in management staff shortly thereafter and the associated restructuring confusion, Commodore stopped developing the Commodore 364 model without further ado. Instead, at the behest of the marketing department, which is now more involved, a version based on the technology of the Commodore 116, housed in an anthracite-colored housing of the Commodore 64 series, called the Commodore 16, was launched. During the same period, a large number of development engineers left Commodore, which meant that the work on the graphical user interface Magic Desk II of the Commodore 264 , which was already in an advanced stage, was now idle. The external company Tri-Micro was hired quickly and was already working on a similar project for the Commodore 64. Owing to the given hardware restrictions of 64 KB RAM along with the lack of file swapping options and the time pressure, clear concessions had to be made to the scope and quality of the replacement software to be converted. As a result, the package, which is now limited to four application programs, fell far short of the expectations raised by its predecessors and previous press releases as a competitor to the market leader Lotus 1-2-3 (with at least 192 KB of RAM required).

In the meantime, Commodore presented the devices at other international trade fairs and explored their sales opportunities. In Germany, for example, the Commodore 264 and the dismantled variants Commodore 16 and Commodore 116 were first seen at the Hanover Fair in spring 1984.

Renamed to Commodore Plus / 4

To prevent confusion with the Commodore 64 and to clear up misunderstandings regarding the capacity of the built-in memory, the Commodore 264 was given a different name in June 1984: The new name Commodore Plus / 4 emphasized in particular the integrated software package 3-plus-1 , a unique selling point of the device on the home computer market. To boost sales, Commodore presented the newly named Commodore Plus / 4 together with the entry-level model Commodore 16, which was declared as a learning computer, in June 1984 at the 5th Commodore Show in London and a little later at the Summer CES in Chicago . In addition to the computers, some of the new peripheral devices in the form of two printers and the Commodore 1531 datasette were also on display.

Commodore transferred the manufacture of the devices, which had meanwhile been brought to production readiness, to various factories in the vicinity of the future sales area: the Commodore factories in Corby in the UK and Braunschweig in West Germany were responsible for supplying the European market . The prefabricated components supplied by the central material procurement office in Hong Kong were finally assembled, tested and distributed in the two plants.

marketing

In order to guarantee a sufficient worldwide supply, Commodore began to pre-produce and store the devices on a large scale after the Summer CES. Due to a global shortage of required components and delays in the completion of the integrated software package, production had to be throttled. The planned sales quotas were only available in autumn 1984.

Premium device

The Commodore Plus / 4, already advertised in the press as the “Productivity Computer” during the development phase, was sold in North America in autumn 1984 at a price of US $ 299. The appearance of the Commodore Plus / 4 was accompanied by suitable peripheral devices in the form of the printer DPS 1101 and MPS 802 as well as the data recorder Commodore 1531 , supplemented by special joysticks that can only be used with the Commodore Plus / 4 . Various games and other software, such as the popular programming language Logo , rounded off the premiere offer. However, sales were sluggish, although the advertising campaign announced the Commodore Plus / 4 early and full-bodied as the “professional successor” for the Commodore 64 and with the slogan “The only computer with four leading software programs built in” (German: “The only one Computer with four built-in industry-leading programs ") had aroused great expectations.

By the late autumn of 1984, corresponding production lines and sales capacities had also been developed in Europe and in smaller sales markets such as New Zealand, accompanied by extensive advertising campaigns and advance announcements in relevant computer magazines. Sales in Europe finally started at the end of the year, initially in the UK, priced at £ 249. In January 1985 the Commodore Plus / 4 was also available in West German retail outlets at a price of around 1300 DM, one month after the Commodore 116 and Commodore 16 premiered for 448 DM and 498 DM respectively.

Bundle offer

Shortly after the market launch, major marketing difficulties for the Commodore Plus / 4 became apparent in Europe, especially in Great Britain. In response, and with regard to the competing models, Commodore's UK subsidiary responded in the spring of 1985 with a price cut to £ 149. This decision also put the price of the Commodore 64 under pressure and had to be lowered as well. A development that drew the resentment of many retailers - it caused profit margins, which were already low in the highly competitive home computer market, to shrink further. Subsequent changes made to the British staff of Commodore led to a change in sales policy towards bundled offers for the Commodore Plus / 4.

At the 6th Commodore Show in June 1985, a bundle offer consisting of the Commodore Plus / 4, 1541 disk drive , the MPS 801 dot matrix printer and the Impex 3-2-1 software was presented for the first time at a retail price of £ 449. This was a complete turnaround from the previous marketing strategy of the "professional home user device" to one of the mass-compatible entry-level all-round package. At Commodore in Germany, the bundled offers of various sizes were also equipped with a programming manual and the instruction cassette BASIC course and declared a computer learning course . This marketing strategy tried to bind customers, who were often completely inexperienced with computers, to the Commodore brand by means of inexpensive lure offers in order to secure their purchasing power for more expensive products such as the Commodore 64 or Commodore 128.

When, with the Sinclair QL , CPC 464 and Atari 800XL, the home computer market began to produce other serious competitors, the already poor sales of the Commodore Plus / 4 collapsed completely. Commodore responded in mid-1985 by stopping production and further reducing prices for devices that were already in production. The unrivaled low prices, meanwhile, resulted in good Christmas sales, which in turn led to an upturn in software supply by third-party manufacturers. The then growing hopes of the users for further support from the manufacturer, however, only lasted briefly: With the release of the new Commodore 128 in view, Commodore finally dropped the Commodore 264 product line in early 1986. The extensive stocks were sold to interested bulk buyers within a short time in batches of up to 150,000 pieces.

Junk goods

In the course of 1986, the buyers began to sell the devices around the world at bargain prices. In Great Britain, for example, the complete Plus Pack package with computer, datasette, joystick and ten cassette games was now available for purchase from £ 99, those with the new Commodore 1551 floppy disk drive and MPS 803 printer and business software from £ 299. The other sellers followed suit and also lowered their prices. In Germany, the Aldi grocery chain in particular began to bring the heavily discounted computer learning course to its branches around May 1986, making the Commodore Plus / 4 and Commodore 16 computers available to a larger group of potential interested parties.

The plummeting prices drew increased interest outside of the western industrialized nations. Many Eastern Bloc countries , whose national computer products were many times more expensive than the Commodore Plus / 4, took the opportunity to purchase larger quantities. Hungary in particular stocked up on the computer and peripheral devices, which were unpopular in the West, in large quantities, with the majority of the technology acquired being used to equip state educational institutions.

According to Tri-Micro, around 600,000 computers had been sold worldwide by the end of 1987. The largest sales market was Europe with around 450,000 units sold, of which around 100,000 were in the Eastern Bloc and mainly Hungary. Including the following years, according to a former Commodore employee, a total of around 830,000 Commodore Plus / 4 computers were sold worldwide, with 286,500 units in Germany in particular. The computer sold significantly worse than the Commodore 64 (3 million units in Germany alone) and VC 20 (2.5 million units worldwide).

Technical details

The housing of the Commodore Plus / 4 contains a single board with all electronic assemblies, the peripheral connections, the external system bus for expansions, the screen output and the voltage control for the external power supply unit. The main electronic components are the 7501 or 8501 CPU ( central processing unit ), the text editing device (TED) and the working memory (RAM) and read-only memory ( ROM ). In addition to the computer, the scope of delivery included a power supply unit (5 V DC , 9 V AC ), the antenna cable and the operating instructions for the device and the built-in software.

Board of the Plus / 4. Hover over the individual components with the mouse pointer to identify them and click for further information.

CPU

→ Main article : MOS Technology 7501

The system architecture is based on the 8-bit microprocessor MOS 7501 or a more modern variant in the form of the MOS 8501 . These are downward-compatible further developments of the 6502 or 6510 microprocessors that are often built into home computers . The CPU can access an address space of 65536 bytes , which also defines the theoretically possible upper limit of the main memory of 64 KB. By switching banks - which is an essential part of the computer architecture of the Commodore Plus / 4 - it is possible to address more than 65536 different bytes by successively fading in further RAM and ROM modules. The system clock for PAL devices is 1.768  MHz , for those with NTSC output it is 1.788 MHz.

In addition to the CPU, the special module TED can also directly access the main memory and the input / output devices ( direct memory access , DMA), for example to generate the image to be displayed from video data. The system switches to shared bus mode, in which the memory accesses of both modules are made in constant change. For the CPU, operations are only possible with even-numbered and for the TED only with odd-numbered clock numbers. This effectively corresponds to halving the CPU clock rate to 884 kHz or 894 kHz. If the TED has no further image data to process, i. H. During horizontal and vertical blanking gaps and when the screen is cleared, all clocks for the CPU are released again - with a few exceptions.

Special module TED

→ Main article : MOS Technology TED

The 48-pin electronic special module MOS 7360 with the abbreviation TED (acronym for Text Editing Device ) contains the essential electronic components for generating graphics and sound as well as for input and output operations. In addition, u. a. also the memory management, the reading of the keyboard entries and the clock generation for its tasks. In contrast to the CPU, the TED cannot access ROM content.

The 48 connections of the TED component shown in circuit symbols

The various television standards ( NTSC , PAL ) are implemented through appropriate external wiring and adjustments to the operating system ("Kernal").

graphic

The data to be made available for the image output device such as monitor or television are generated by the TED from the image and color data stored in the main memory. The image generator contained in the TED enables the output of 320 pixels for 200 television lines. The data obtained from the video and color memory can be interpreted differently depending on the working mode of the TED and thus displayed differently. Elements with a size of 8 × 8, 2 × 1 and 1 × 1 pixels for resolutions of 40 × 25 characters and point graphics with 160 × 200 and 320 × 200 pixels (acronym for picture cell , graphic block) are supported. The various graphic operating modes can be mixed on the screen in a vertical sequence by means of raster interrupt programming.

The appearance of the video memory stored text character is represented by a maximum of 256 characters comprehensive character set defined. The character color is specified via an assigned byte in the color memory , the attribute . In addition to black, the available color plate includes 15 other colors, each in eight different levels of brightness. At the graphics level with the highest resolution, the color of the individual pixels - similar to the text mode - is always the same within an area of ​​8 × 8 pixels, but can be freely selected from the 121 possible per area.

In multi-color mode for both text and graphics, the data stored in the memory are interpreted differently by the TED than in normal mode. This means that more colors can be displayed at the same time in the 8 × 8 pixel areas - but the horizontal resolution of the pixels is halved and the available colors are reduced to a total of eight and the corresponding brightness levels. For text display, a further operating mode ( extended color mode ) with an increased number of colors is possible with the same resolution as in the multi- color mode, but at the expense of a reduced selection of characters (64 instead of 256).

In contrast to many other contemporary home computers, graphic blocks ( hardware sprites ) that can be moved independently of the background are not integrated in the Commodore Plus / 4. On the other hand, a soft fine adjustment ( scrolling ) for easy-to-eye movement of the entire screen content is supported.

Sound generation

The two separate generators "Voice 1" and "Voice 2", which can each generate a square wave, are used to generate the sound. Associated vibration parameters such as amplitude (volume), frequency (pitch) and tone duration can be freely set and thus varied by the user over time. It is not possible to change the waveform ("tone color") in sine or sawtooth form, as is the case with the sound chip of the Commodore 64; by combinations of the individual channels but sound technology can interesting beats are generated. In addition, one of the two audio channels can be used to generate white noise (“Voice 3”), i. H. can be used for certain sound effects such as noises or as a random number generator .

Memory allocation, RAM and ROM, bank switching

The address space that can be addressed by the CPU and TED is segmented in the Commodore Plus / 4 into different sections of different sizes. For practical reasons, it is common for their addresses instead of decimal notation , the hexadecimal to use. It is usually preceded by a $ symbol to make it easier to distinguish. The addresses from 0 to 65535 in decimal notation correspond to addresses $ 0000 to $ FFFF in the hexadecimal system.

After switching on the computer, the address space consists of almost 32 KB RAM ($ 0002 to $ 07FF for system and BASIC variables, $ 0800 to $ 0BFF as color memory for text mode, $ 0C00 to $ 0FFF as video memory for text mode, from $ 1000 to $ 7FFF free) followed by around 32 KB of ROM ($ 8000 to $ BFFF for the BASIC interpreter, $ C000 to $ FFFF for the operating system, $ D000 to $ D7FF for the character set, $ D800 to $ FCFF and $ FF40 to $ FFFF for the operating system). The other areas are reserved for input and output operations ($ 0000, $ 0001, $ FD00 to $ FEFF) and the control of the TED ($ FF00 to $ FF3F). The CPU first reads out the contents of the ROM modules with the operating system, which initializes the Commodore Plus / 4 and connected peripheral devices. If there are no plug-in modules with executable content on the expansion port, the operating system starts the built-in BASIC and a switch-on message with a blinking cursor appears on the screen.

During the initialization, the user can switch to the ROMs with the integrated application programs. If only RAM is shown, minus the reserved areas and the areas required for system maintenance, 60,671 bytes are available for use with BASIC or the 3-plus-1 software package. The change between the different RAM or ROM memory banks, the bank switching , is controlled by the operating system.

Input and output, interfaces

An expansion slot (system bus), two joystick connections in mini-DIN format, a monitor socket, a coaxial RF antenna connection for television, a socket for connecting to the Datasette Commodore 1531 , a serial Commodore standard interface for use with, serve as connections to the outside world many Commodore peripheral devices such as the 1541 floppy disk drive and an RS-232 interface in the form of the user port . Its control is handled by a special component only installed in the Commodore Plus / 4, the MOS 6551 or MOS 8551 (ACIA).

• 

  Rear view with power supply socket, SIO socket, datasette connection, user port, expansion port, joystick sockets and monitor socket

• 

  Right side with reset button and power switch

• 

  Left side with RF output and channel selector switch

Peripherals

Mass storage

In connection with mainly western home computers from the 1980s, cassette recorders and floppy disk drives were mainly used for data backup , while hard and removable disk drives were increasingly used in the professional environment for personal computers . The cheapest variant of data recording using compact cassettes generally has the disadvantage of low data transfer rates and thus long loading times, whereas the much faster and more reliable floppy and disk drives were much more expensive to purchase. When the Commodore Plus / 4 was released, cassette and diskette systems were available as mass storage devices.

Cassette systems

Datasette Commodore 1531

The Commodore Plus / 4 has a cassette interface ex works for data exchange with the Datasette Commodore 1531 . Operation with the rest of the datasettes produced by Commodore, such as the 1530 model, is only possible with an appropriate adapter from third-party manufacturers. Compact cassettes are used as storage media . As with the Commodore 64 and VC 20, the average data transfer rate is also around 300 bit / s. This low value compared to other contemporary home computers (600 bit / s with Atari home computers , 1500 bit / s with ZX Spectrum ) is due to the complex data format with double redundant blocks and checksum validation. By changing this recording format with special programs, the Turbo Tapes, such as CSJ Turbo Tape and Turbotape C16 , the loading speed can be increased by a factor of 12.

Floppy disk systems

→ Main article : Commodore floppy disk drives

The Commodore 1541 (5¼ "), Commodore 1570 (5¼"), Commodore 1571 (5¼ ") and Commodore 1581 (3½") floppy drives can be operated with the Commodore Plus / 4 via the standard serial interface . Using the accelerated data transfer ( burst mode ) of the non-1541 models is not possible. The average data transfer rate for the older version of the 1541 diskette station is around 1200 bps, which is a low rate compared to other home computer systems.

In addition, Commodore produced a floppy disk drive specially developed for the Commodore 16, 116 and Plus / 4, the data of which is transferred via a parallel interface, the expansion port. Unspecified problems delayed the release of this 5¼-inch floppy disk drive, initially known as SFS 481 . Renamed in the meantime to Commodore 1551 , it was only available from mid-1986, often as part of one of the many sale bundle offers. The device, which is also available individually at an introductory price of DM 400, has a number of significant advantages over the older 1541 model: The more robust mechanics and new control electronics significantly increase reliability; the parallel connection means the data transfer rate is around 6000 bit / s. The instruction set of both drive operating systems ( DOS ) is almost identical, so that 1541 diskettes can be used with the 1551 diskette station and - apart from a few special cases - also vice versa.

In addition to the Commodore's own floppy disk drives, the Commodore Plus / 4 can also be operated with devices from third-party manufacturers such as the Enhancer 2000 from Comtel Group.

• 

  Front with power light (green light emitting diode ), activity indicator (red light emitting diode) and toggle mechanism with inserted transport lock

• 

  Rear with power switch, IEC socket, fuse and connection cable for the computer

• 

  Right side with ventilation slots for the built-in power supply unit

• 

  Connector for the expansion port on the computer

Output devices

→ Main articles : Commodore monitors  and Commodore printers

The Commodore Plus / 4 has various options for data output: The computer can be operated with the Commodore color monitors, for example, via a special monitor output, whereby the Commodore 1703 with its darker housing was specially designed for the Commodore 16 and Commodore Plus / 4. In addition to the monitor output, the TV modulator can also be used to display it on a standard television, whereby the image quality is to be classified as significantly poorer.

Various Commodore printers are used to fix text or graphics in writing. These include the needle-based models MPS 801 to 803 , the type wheel printer DPS 1101 with typewriter quality and the four-color Commodore 1520 plotter . In addition, many printer models from third-party manufacturers such as Seikosha, Brother or Star can be operated with the Commodore Plus / 4.

Input devices

The keyboard built into the Commodore Plus / 4 has 67 keys in a QWERTY arrangement with four separate cursor keys. Outside the actual keypad there are four freely programmable and double-assignable function keys.

In contrast to many other home computers of its time, the joystick connections of the Commodore Plus / 4 do not follow a common standard. Rather, it is a technical island solution that is due to the limited space in the small housing. Adapters released later by third-party manufacturers allow, in addition to the operation of the joysticks specially designed for the Commodore Plus / 4, the connection of the widespread Atari 2600- compatible models ( D-Sub : two-row 9-pin) such as the Competition Pro joystick or one Representative of the Quickshot series from Spectravideo .

Remote data transmission

With the help of the UART interface built into the Commodore Plus / 4 in the form of the MOS 6551 , RS-232 high-speed modems of the time can be operated without further software support. However, in 1984 only very few users had modems with higher data transfer rates than were possible with the Commodore 64 using software emulation. Initially, only the Commodore 1660 telephone modem was used.

software

Screwed on plug-in module with printed circuit board and software on ROM

As with other home computers of the 1980s, commercial software was distributed on various data carriers. The inexpensive compact cassettes, particularly popular with game manufacturers, were, however, very prone to errors due to the high mechanical stress on the magnetic tape, and their use was often associated with long loading times. In addition, certain operating modes, such as relative addressing, which is advantageous for operating databases, are not possible with datasettes. In the case of the plug-in modules, which are much more expensive to manufacture, the programs contained therein were available immediately after switching on the computer, which was a great advantage in particular for system software and frequently used applications. The best compromise between loading time, possible operating modes, reliability and storage capacity was achieved by the diskettes, the use of which was supported by the 1541 diskette drive when the Commodore Plus / 4 was released.

The range of programs for the Commodore Plus / 4 computer included the selection of commercial programs sold by Commodore as well as software ( listings ) developed by third-party manufacturers and published in magazines and books . Most of the commercial programs were offered on cartridge and floppy disk. In contrast, games, especially those from third-party manufacturers, were often only available on compact cassettes.

Illegal copies ("pirated copies") always made up a large part of the software in circulation and often presented small software developers with existential economic difficulties. As a result, copy protection systems were increasingly used, especially in games, as the best-selling software.

System programs

The configuration of the Commodore-Plus / 4 hardware and the BASIC falls within the scope of the operating system, for which the name Kernal has become established in normal usage . The operating system consists of a total of 39 subroutines; they control the input / output operations, access to system variables, memory management and the operation of the BASIC interpreter. The start addresses of the individual subroutines are summarized in a jump table to be used by the user in order to ensure the software compatibility of the programs created with Commodore 16, Commodore 116 and future revisions of the operating system.

Programming languages ​​and application programs

Based on the system software, the user-specific use of the Commodore Plus / 4 in a wide variety of application areas was of great importance. Was the processing of a task with z. For example, programs that can be purchased are not possible for technical or economic reasons, or if, for example, new types of entertainment software are to be produced, this had to be done independently with the help of the appropriate programming languages.

Assembly language

In the early 1980s, the creation of time-critical action games and applications in control engineering required optimal use of the hardware, in particular the main memory. In the home computer sector, this was only possible through the use of assembly language with appropriate translation programs, the assemblers . In many cases assemblers were delivered with an associated editor for entering the program instructions (“source code”), often also as a program package with debugger and disassembler for error analysis. In the professional development environment, cross assemblers were often used. This made it possible to generate executable programs for home computers on more powerful and easy-to-use third-party computer platforms. For example, the Commodore Plus / 4 system software was developed on a VAX computer from DEC .

For programming in machine language , the Commodore Plus / 4 user can use the TEDMON monitor integrated in the system ROMs , which can be started, for example, by entering a BASIC command. In addition to displaying, editing and manipulating memory and register contents, you can also create your own simple assembler programs, for example to be called by BASIC. Due to the lack of functionalities such as breakpoints , integrated text data format, jump labels or macro definitions , creating larger programs and analyzing errors is difficult and therefore the use of more comfortable alternatives such as the 6502 Editor / Assembler Plus / 4 from York Electronic Research is recommended.

In many cases, programming beginners preferred the clear and easy-to-use, but less powerful, high-level programming languages.

Interpreter high-level languages

→ Main article : Commodore BASIC

BASIC 3.5 programming screen

The BASIC 3.5, which is delivered together with the Commodore Plus / 4 and is easy to learn, enables the implementation of larger projects as well as appealing graphics thanks to its powerful set of over 75 commands and the available 60,671 bytes of RAM. The fundamental limitations inherent in the nature of the interpreter , such as the low execution speed and the large amount of memory required, had a disadvantageous effect on the usability of BASIC programs . These disadvantages can be mitigated by special programs, BASIC compilers . Executable machine programs are generated that can run without a BASIC interpreter and thus often allow faster execution. With the Austrospeed +4 compiler, released in 1987 , significant speed advantages are achieved, especially when reading diskette files (up to 20 times faster) and with certain sorting algorithms (up to four times faster).

After many computers had found new owners as part of the sell-off that began in 1986, especially in Germany and Hungary, optimized BASIC dialects were offered there from 1986 onwards due to the increased demand . Turbobasic (1986), Markt & Technik Basic (1986) and Sprite-Basic (1988) are representative of German programs ; as the Hungarian representative Lacisoft Basic , Octasoft BASIC V7.0 (1988) and Tool Basic 7.0 (1989).

In addition to the BASIC programming language in its various dialects, there is the logo interpreter language , which has been available since the Commodore Plus / 4 was launched. Supported by elements such as turtle graphics ( turtle graphics ), a child-friendly and interactive introduction to the basics of programming is possible. Logo was only supplied on floppy disks, which means that a floppy disk drive is required for operation.

Compiler high-level languages

As a middle ground between high-level interpreter language (slow to execute, but easily readable source codes and simple error analysis) and assembly language (difficult to learn and cumbersome to use, but no alternative to generating faster and memory-efficient programs at the beginning of the 1980s), they also established themselves in the home computer sector During the 1980s the high-level compiler languages. The execution speed of the machine programs generated with it was much faster compared to interpreted programs such as the built-in BASIC, but did not quite reach that achieved by assemblers. However, the speed disadvantages compared to assembled programs were often accepted in favor of an easier-to-maintain source code .

Over time, compiler languages ​​such as G-Pascal and various versions of Forth became available for Commodore Plus / 4 users .

Application software

In addition to the programming languages ​​for creating your own applications, the range of programs for the Commodore Plus / 4 includes only a small selection of ready-made commercial application software compared to the Commodore 64.

The integrated 3-plus-1 software package consists of four closely interlinked application programs, the data of which can be easily exchanged with one another using a simple window-based user interface. The built-in word processing with its limited range of functions (formatting commands, search, character replacement, output of 80 characters per line supported) and the cumbersome operation ( control characters only effective when printing) is not suitable for professional purposes, just like the spreadsheet, whose tables are due to the maximum screen column width of only 40 characters can only display small sections (3 × 12 of 17 × 50 fields) and is therefore very confusing. In addition, the graphics program supplied for displaying the table data does not by any means use the capabilities of the TED, so that the series of numbers can only be visualized in the form of roughly resolved bar charts. With a maximum of 17 fields of 38 characters each and thus a total of only 999 information that can be stored, the file management also meets non-professional requirements such as use in warehousing .

In the course of time, Commodore expanded the program library to include more powerful business programs such as Script / Plus , Calc / Plus and Financial Advisor in the form of plug-in modules. In addition, a large number of applications appeared on diskette and cassette, mainly in Europe and particularly in Hungary.

Games

By far the largest part of the commercial as well as freely available Commodore Plus / 4 software are the games. The most popular were primarily implementations of arcade games . In addition to Commodore, Scott Adams' Adventure International and Infocom , low-budget manufacturers such as Anirog, Kingsoft (Anco), Mastertronic , Microdeal and Tynesoft published for the Commodore Plus / 4. Apart from the plug-in module titles produced by Commodore, commercial Commodore Plus / 4 games were mostly delivered on compact cassettes with quick loading programs and often combined copy protection mechanisms. In 1987 there were over 150 commercial titles available in Germany at prices between DM 10 and DM 40. Games were also developed and distributed in what was then the Eastern Bloc , such as B. Hungaroring .

Magazines

In the 1980s, along with specialist books, computer magazines played a major role for many home computer owners. The editions, which were often published monthly, contained test reports on innovations, programming instructions and software for typing. They also served as an advertising and information platform as well as for establishing contact with like-minded people.

Various kiosk and subscription publications tailored to their needs were available for the Commodore Plus / 4 users. In West Germany these were often special editions of popular commercial computer magazines such as 64'er or Compute mit .

emulation

After the end of the home computer era in the early 1990s and with the advent of powerful and affordable computing technology in the late 1990s, dedicated enthusiasts increasingly developed programs for emulating home computers and their peripheral devices. To play old classics of various home computer systems, a single modern system with data images of the corresponding home computer programs was sufficient with the help of the emulators. The emergence of the emulators continued, among other things. a. an increased transfer of otherwise possibly lost software to modern storage media, which makes an important contribution to the preservation of digital culture.

The most powerful emulators for Windows and Linux systems are the Versatile Commodore Emulator ( VICE ), Yet Another Plus / 4 Emulator (YAPE) and plus4emu .

reception

Contemporary

The small and compact housing, the large main memory, the extended BASIC 3.5 with its extensive instruction set, the good graphic possibilities of the TED ("color wonder"), the built-in assembler and the support of the 1541 floppy disk drive already available in many places were very well received in the trade press. Thus, the performance of the device was mainly classified as being up to date. Only when it came to the price did the opinions differ: opinions were divided into “justified” and “unjustified”.

The disadvantages of the hardware described in the reviews mainly relate to the differences to the previous models Commodore 64 and VC 20. The main point of criticism was the lack of downward compatibility and the lack of software for the Commodore Plus / 4. In addition, the incompatible connections for joystick and datasette as well as the non-standardized RS-232 interface often aroused the disapproval of the testers. In addition to the mostly expensive software from the Commodore 64 and VC 20, certain existing peripheral devices such as standard joysticks could not be used with the Commodore Plus / 4, a circumstance that met with complete incomprehension and constant rumors about Commodore's true intention - the pure profit maximization through expected accessory sales - nourished.

The unique selling point of the computer, the integrated software, advertised by Commodore, gave an idea of ​​only limited usability after the first trade fair presentations. After the start of sales and more detailed tests, the worst fears were confirmed, because the built-in software turned out to be completely unsuitable for professional purposes in terms of functionality and manageability. To make matters worse, the use of a floppy disk drive and thus additional purchases were required.

After the limitations of the device and its built-in software had crystallized more and more clearly, the question of the purpose and target group of the Commodore Plus / 4 increasingly arose. Due to the additional hidden costs for new software and peripheral devices, the trade press often considered the purchase of a Commodore 64 system with additional software to be the more sensible option, even for users as the target group targeted by Commodore:

"Anyone who can afford the lower-priced Commodore 64 and specifically buy software for it is probably better served than with the Plus / 4 and its integrated programs."

- Heinrich Lenhardt : Happy Computer 2/1985

A short time after the market launch, the sales misery of the Commodore Plus / 4, accompanied by drastic words such as "the more or less failed C16 and Plus / 4" (Commodore Horizons, June 1985), became more and more apparent. As a result of the subsequent drop in prices, according to many computer magazines, the price-performance ratio improved and the computer was viewed with goodwill in Europe and especially in West Germany - the modern technology, BASIC 3.5 and the additional programs are ideal for introducing newbies suitable for computer technology:

“The Commodore Plus / 4 offers remarkable performance for a home computer. Due to the significantly lower price and the rich software equipment, this computer is particularly suitable for beginners. An offer that is not available every day. "

- Jürgen Zumbach : Happy Computer 12/1986

Retrospective

The Commodore Plus / 4 is meanwhile experiencing increased awareness on the Internet, in magazines and books and is seen in retrospect as a prime example of the accumulation of unfortunate circumstances, coupled with a lack of concept and poor marketing.

The time chosen for the realization of the Commodore Plus / 4 turned out to be unfavorable in the opinion of Ian Matthews, because the overpowering Commodore 64 would have always cast its long shadow over the Commodore Plus / 4 project. The well-being of the Commodore 64 dominated company policy and claimed the majority of resources and manufacturing capacities. This was at the expense of the timely completion of the Commodore Plus / 4 and, according to Matthews, led to a postponement of the start of sales with correspondingly negative marketing consequences. Matthews sums up his view of Commodore's marketing policy as follows:

"One thing Commodore did well with the" TED "series was to color them black, so they were correctly dressed for their own funerals."

"The black coloring of the TED series was a good decision by Commodore, because the devices were appropriately equipped for their funeral."

- Ian Matthews

According to other authors, the sales strategy practiced at Commodore, namely always wanting to bring new software and peripheral devices to the buyer with new computers, turned out to be wrong in the case of the Commodore Plus / 4 - only a fraction of the potential customers have already acquired expensive ones Buy software and hardware again for a device that is only slightly more powerful and want to laboriously convert previously created databases.

The use of the "cheap chip TED" (Stefan Egger, SCACOM 20/21), tailored to the originally planned Sinclair competitor, and the associated lack of sprites and sound generation possibilities, according to the US computer magazine Commodore World and the German author couple Allner, besides the incompatibilities one more thing to deter "the market", who would have expected a full-fledged successor to the Commodore 64.

Completely announced components such as the freely selectable software, which were dropped in favor of permanently installed software that was also assessed as very poor ("Tri-Micro's 3 Plus 1 software is best described as barely stable."), Would still have the last one, according to Matthews remaining target group of home users pissed off.

literature

• Fritz Schäfer: The big plus / 4 book. Kingsoft Fritz Schäfer, 1986.
• Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. 6th edition, Scott, Foresman and Company, 1990, ISBN 0-673-18249-5 .
• Sarah Meyer: The Commodore Plus / 4 Book. 1st edition, SAMS Computerfacts, 1984, ISBN 0-672-22389-9 .

Web links

Commons : Commodore Plus / 4  - Collection of images, videos and audio files

• Commodore Plus / 4 World (English)
• History of Commodore 264 series (English)
• Prototypes of the Commodore 264 series

Remarks

1. ^ ^{A b} Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , pp. 182-185.
2. ^ ^{A b} Benn Dunnington: The Plus / 4.  - Internet Archive In: Info 64 , Issue 5, 1984, p. 28.
3. ^ ^{A b} New CBM micros debut at show.  - Internet Archive In: Commodore Horizons , August 1984, p. 6.
4. ↑ ^{a b c d e} Heinrich Lenhardt: The Plus / 4 is finally here  - Internet Archive In: Happy Computer , February, 1984, p. 12.
5. ↑ Leo Sorge: Commodore Plus / 4. (PDF) MCmicrocomputer, March 1985, p. 47.
6. ^ Stefan Egger: Commodore Plus / 4. scacom.bplaced.net, accessed September 12, 2014 . 
7. ^ ^{A b} Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , p. 178.
8. ↑ ^{a b c d} Stefan Egger: Three bad ideas. SCACOM-Aktuell, edition 20/21, 2010, p. 26.
9. ^ Scott Mace: Commodore enhances 264. InfoWorld, July, 1984, p. 11.
10. ^ Morton Kevelson: What's Inside the Plus / 4?  - Internet Archive In: Ahoy! , March 1983, p. 29.
11. ↑ Rumor, Innoendo and TED  - Internet Archive In: Ahoy! , February 1984, p. 14.
12. ↑ New one soon from Commodore?  - Internet Archive In: Bits & Bytes , February 1984, p. 2.
13. ↑ Software on the move.  - Internet Archive In: Baron's MicroComputing Reports , May, 1984, p. 7.
14. ^ ^{A b} Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , pp. 188 f.
15. ↑ Michael Scharfenberger: 264 and 364 - The new ones from Commodore.  - Internet Archive In: Happy Computer , Edition 3, 1984, pp. 10 f.
16. ↑ The picture is a photo montage based on a template from Compute! Magazine (April 1986, p. 16).
17. ↑ Die Neuen - 264 und 364 64'er, Edition 4, 1984, pp. 9-11.
18. ↑ Mickey McLean: 80s Ups and Downs.  - Internet Archive In: Compute! 'S Gazette , January 1990, p. 18.
19. ^ Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , p. 199.
20. ^ Selby Bateman: The move toward integrated software.  - Internet Archive In: Compute! 'S Gazette , January 1985, pp. 27 f.
21. ↑ Dietmar Eirich: Computer Yearbook '86. Heyne, 1985, ISBN 3-453-47056-7 , p. 55.
22. ^ Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , p. 202.
23. ↑ Editorial.  - Internet Archive In: Commodore Horizons , June, 1984, p. 3.
24. ↑ The CBM-PC?  - Internet Archive In: Ahoy! , June, 1984, p. 7.
25. ↑ Commodore 16.  - Internet Archive In: Ahoy! , September 1984, p. 7.
26. ^ Taking care of business.  - Internet Archive In: Commodore Horizons , July, 1984, p. 7.
27. ↑ ^{a b c d e f g} Ian Matthews: Commodore "TED" 264 Series: The Beginning of the End. (No longer available online.) Commodore.ca, January 13, 2008, archived from the original on February 23, 2006 ; Retrieved September 12, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
28. ^ Commodore Story. In: Diskmagazin Zine # 3 , 1990.
29. ↑ Chris Jenkins: Corby on stream.  - Internet Archive In: Commodore Horizons , September 1984, p. 7.
30. ↑ Horst Höfflin: Hong Kong made - made in Germany. In: RUN , August 1984, p. 8 f.
31. ^ Peter Ensor: Commodore Plus / 4.  - Internet Archive In: Bits & Bytes , May 1985, p. 18.
32. ^ Commodore Horizons: New CBM micros debut at show.  - Internet Archive August 1984 edition, p. 6.
33. ↑ Axel Arberle: The great Commodore Show.  - Internet Archive In: Computer Kontakt Magazin , Issue 11, 1984, p. 54.
34. ↑ Andreas Hagedorn: Is he coming or not?  - Internet Archive In: Happy Computer , December 1984, p. 159.
35. ↑ Editorial.  - Internet Archive In: Computer Horizons , March 1984, p. 3.
36. ↑ Plus / 4 and C16 go down.  - Internet Archive In: Commodore Horizons , April 1985, p. 8.
37. ^ Bessey means business.  - Internet Archive In: Commodore Horizons , July 1985, p. 34.
38. ↑ Show-stopping C128.  - Internet Archive In: Commodore Horizons , August 1985, p. 8.
39. ^ ^{A b} Andrew Farrel: From PET to CDTV.  - Internet Archive In: The Australian Commodore and Amiga Review , September 1991, p. 18.
40. ↑ New marketing idea could catch on: Commodore offers C16 over Aldi counters. In: Computerwoche , April 4, 1986.
41. ↑ Plus / 4 revival?  - Internet Archive In: Commodore Horizons , March 1986, p. 7.
42. ↑ Plus / 4 deal secured by Commodore.  - Internet Archive In: Commodore Computing International , February 1986, p. 3.
43. ↑ Tony Lyon: The Commodore Plus / 4. retrovideogamesystems.com, March 21, 2010, accessed September 12, 2014 . 
44. ↑ Jürgen Zumbach: Commodore Plus / 4, the power package.  - Internet Archive In: Happy Computer , December 1986, p. 34.
45. ^ Christian Zahn, Boris Kretzinger, Enno Coners: The Commodore Story. CSW Verlag, 2013, ISBN 978-3-941287-35-8 , p. 60.
46. ^ David Johnson: Truth and its consequences. ( Memento of May 28, 2003 in the Internet Archive ) Tri-Micro, 1987, p. 29.
47. ^ Stefan Egger: Commodore Plus / 4. Retrieved August 31, 2014.
48. ↑ Commodore International: TED System Hardware Manual. P. 35.
49. ↑ Commodore International: TED System Hardware Manual. P. 3.
50. ↑ David W. DiOrio: Video and sound system control circuit. Patent US 4569019 A, filed 1983, published 1986.
51. ↑ Commodore International: TED System Hardware Manual. P. 4.
52. ^ Fritz Schäfer: Das große Plus / 4 book Kingsoft, 1986, p. 49.
53. ↑ Commodore International: TED System Hardware Manual. P. 30.
54. ^ Fritz Schäfer: Das große Plus / 4 Buch Kingsoft, 1986, p. 47.
55. ↑ B. Mangelsdorff: Game sounds for the C16 and Plus / 4. 64'er, special issue 14, 1987, p. 158.
56. ↑ Commodore International: TED System Hardware Manual. P. 24.
57. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , pp. 303 f.
58. ↑ Commodore International: TED System Hardware Manual. P. 4.
59. ↑ Dietmar Eirich: Computer Periphery. Heyne, Munich 1985, ISBN 3-453-47058-3 , pp. 51-53.
60. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , p. 360.
61. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , p. 323.
62. ↑ Gerd Donaubauer: C16 and diskette - speed is not witchcraft. 64'er, special issue 3, 1986, p. 49.
63. ↑ Thomas Röder: CSJ Turbo Tape. 64'er, special issue 14, 1987, p. 77.
64. ↑ Andreas Jung: Load faster with the datasette. 64'er, special issue 14, 1987, p. 156.
65. ↑ Karsten Schramm: C16 and diskette - speed is not witchcraft. In: 64'er , special issue 9, 1986, p. 7.
66. ↑ Commodore VC1551 floppy.  - Internet Archive Vobis advertisement. In: Happy Computer , July, 1986, p. 5.
67. ↑ Karsten Schramm: C16 and diskette - speed is not witchcraft. In: 64'er , special issue 9, 1986, p. 8 f.
68. ↑ Is there compatible hardware?  - Internet Archive Tri-Micro In: Plus Exchange , p. 11.
69. ↑ Selby Bateman: Commodore's New Computer Family.  - Internet Archive In: Compute! Gazette , April 1984, p. 18
70. ↑ The monitor dilemma. In: Data Welt , summer 1984, p. 15.
71. ↑ Gerd Donaubauer: Printer for C16. 64'er, special issue 3, 1986, pp. 43-47.
72. ↑ Richard Evers: The Plus 4 - A Quick Overview  - Internet Archive In: The Transactor Magazin , July 1985, p. 56.
73. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , p. 390.
74. ↑ Jörg Kähler: Commodore C16-Plus / 4-Joystick. In: 64'er , special issue 14, 1987, pp. 13-15.
75. ↑ Telecommunications hardware (sic!) And software.  - Internet Archive Tri-Micro. In: Plus Exchange , p. 5.
76. ↑ Germano Caronni: Managing data with the C16 and Plus / 4. 64'er, special issue 14, 1987, p. 61.
77. ↑ Dietmar Eirich: Computer for reference. Compact Verlag, 1989, ISBN 3-8174-3564-9 , p. 212.
78. ^ Fritz Schäfer: Das große Plus / 4 Buch Kingsoft, 1986, pp. 99 and 101.
79. ↑ CQ Spitzner: Kernel complete - All routines of the C16, C116 and Plus / 4. 64'er, special issue 14, 1987, p. 53.
80. ↑ U. Schollwöck: Machine language on the Dragon 32/64. 1984, p. 6.
81. ^ Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , p. 186 f.
82. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , p. 228.
83. ↑ Thomas Tieke, Gottfried Knechtel: Super assembler with command extension. 64'er, special issue 3, 1986, p. 166.
84. ↑ Cyndie Merten, Sarah Meyer: Programmer's Reference Guide for the Commodore Plus / 4. Scott, Foresman and Company, 1986, ISBN 0-673-18249-5 , p. 304.
85. ↑ Michael Thomas: Austrospeed +4. 64'er, special issue 14, 1987, p. 78 f.
86. ↑ ^{a b c} Four times better. Computer course, booklet 20, p. 534 f.
87. ↑ Jürgen Zumbach: Software for C16 / C116 and Plus / 4.  - Internet Archive In: Happy Computer , February 1987, p. 161.
88. ↑ Andreas Lange: What archives, museums and libraries can learn from gamers - and vice versa. Retrieved February 23, 2014.
89. ↑ emulation. Retrieved September 17, 2014 . 
90. ↑ Computer course booklet 20, p. 535.
91. ^ Peter Ensor: Commodore Plus / 4.  - Internet Archive In: Bits & Bytes , May 1985, p. 20.
92. ↑ ^{a b} Keith and Steven Brain: Plus / 4 - the verdict.  - Internet Archive In: Commodore Horizons , November 1984, p. 15.
93. ↑ CQ Spitzner: Graphics and sound with the C16. In: 64'er , special issue 3, 1986, p. 21.
94. ^ Peter Ensor: Commodore Plus / 4.  - Internet Archive In: Bits & Bytes , May, 1985, p. 18.
95. ^ Commodore's GM.  - Internet Archive In: Commodore Horizons , June 1985, p. 9.
96. ↑ Jürgen Zumbach Commodore Plus / 4, the power package.  - Internet Archive In: Happy Computer , December 1986, p. 34.
97. ^ Brian Bagnall, Boris Kretzinger, Winnie Forster: Volkscomputer. Gameplan, 2010, ISBN 978-3-00-023848-2 , pp. 202-204.
98. ^ Jörg and Kerstin Allner: Computer Classics. Data Becker, 2003, ISBN 978-3-8158-2339-2 , p. 93.
99. ↑ Jim Brain: Hardware Collectables - The Commodore 264 Series.  - Internet Archive In: Commodore World , August / September 1995, p. 38.

This article was added to the list of excellent articles on November 22, 2014 in this version .

	This article is available as an audio file:
	Save | Information  | 78:14 min (35.6 MB) Text of the spoken version (January 8, 2015)
	More information on spoken Wikipedia