The Atari ST is a line of home computers from Atari Corporation and the successor to the Atari 8-bit family. The initial ST model, the 520ST, saw limited release in April–June 1985 and was available in July; the Atari ST is the first personal computer to come with a bitmapped color GUI, using a version of Digital Research's GEM released in February 1985. The 1040ST, released in 1986, is the first personal computer to ship with a megabyte of RAM in the base configuration and the first with a cost-per-kilobyte of less than US$1; the Atari ST is part of a mid-1980s generation of home computers that have 16 or 32-bit processors, 256 KB or more of RAM, mouse-controlled graphical user interfaces. This generation includes the Macintosh, Commodore Amiga, Apple IIGS, and, in certain markets, the Acorn Archimedes. "ST" stands for "Sixteen/Thirty-two", which refers to the Motorola 68000's 16-bit external bus and 32-bit internals. The ST was sold with the less expensive monochrome monitor; the system's two color graphics modes are only available on the former while the highest-resolution mode needs the monochrome monitor.
In some markets Germany, the machine gained a strong foothold as a small business machine for CAD and desktop publishing work. Thanks to its built-in MIDI ports, the ST enjoyed success for running music-sequencer software and as a controller of musical instruments among amateurs and well-known musicians alike; the ST was superseded by the Atari STE, Atari TT, Atari MEGA STE, Falcon computers. The Atari ST was born from the rivalry between home-computer makers Atari, Inc. and Commodore International. Jay Miner, one of the original designers for the custom chips found in the Atari 2600 and Atari 8-bit family, tried to convince Atari management to create a new chipset for a video game console and computer; when his idea was rejected, Miner left Atari to form a small think tank called Hi-Toro in 1982 and began designing the new "Lorraine" chipset. The company, renamed Amiga Corporation, was pretending to sell video game controllers to deceive competition while it developed a Lorraine-based computer.
Amiga ran out of capital to complete Lorraine's development, Atari, owned by Warner Communications, paid Amiga to continue development work. In return Atari received exclusive use of the Lorraine design for one year as a video game console. After one year Atari would have the right to add a keyboard and market the complete computer, designated the 1850XLD; as Atari was involved with Disney at the time, it was code-named "Mickey", the 256K memory expansion board was codenamed "Minnie". After leaving Commodore International in January 1984, Jack Tramiel formed Tramel Technology with his sons and other ex-Commodore employees and, in April, began planning a new computer; the company considered the National Semiconductor NS320xx microprocessor but was disappointed with its performance. This started the move to the 68000; the lead designer of the Atari ST was ex-Commodore employee Shiraz Shivji, who had worked on the Commodore 64's development. Atari in mid-1984 was losing about a million dollars per day.
Interested in Atari's overseas manufacturing and worldwide distribution network for his new computer, Tramiel negotiated with Warner in May and June 1984. He bought Atari's Consumer Division in July; as executives and engineers left Commodore to join Tramiel's new Atari Corporation, Commodore responded by filing lawsuits against four former engineers for theft of trade secrets. The Tramiels did not purchase the employee contracts when they bought the assets of Atari Inc. so one of their first acts was to interview Atari Inc. employees to decide whom to hire at what was a brand new company. This company was called TTL renamed to Atari Corp. At the time of the purchase of Atari Inc's assets, there were 900 employees remaining from a high point of 10,000. After the interviews 100 employees were hired to work at Atari Corp. At one point a custom sound processor called AMY was a planned component for the new ST computer design, but the chip needed more time to complete, so AMY was dropped in favor of an off-the-shelf Yamaha sound chip.
It was during this time in late July/early August that Leonard Tramiel discovered the original Amiga contract, which required Amiga Corporation to deliver the Lorraine chipset to Atari on June 30, 1984. Amiga Corp. had sought more monetary support from investors in spring 1984. Having heard rumors that Tramiel was negotiating to buy Atari, Amiga Corp. entered into discussions with Commodore. The discussions led to Commodore wanting to purchase Amiga Corporation outright, which Commodore believed would cancel any outstanding contracts, including Atari's. Instead of Amiga Corp. delivering Lorraine to Atari, Commodore delivered a check of $500,000 to Atari on Amiga's behalf, in effect returning the funds Atari invested into Amiga for the chipset. Tramiel countersued Amiga Corp. on August 13, 1984. He sought an injunction to bar Amiga from producing anything with its technology. At Commodore, the Amiga team was in limbo during the summer of 1984 because of the lawsuit. No word on the status of the chipset, the Lorraine computer, or the team's fate was known.
In the fall of 1984, Commodore informed the team that the Lorraine project was active again, the chipset was to be improved, the operating system developed, the hardware design completed. While Commodore announced the Amiga 1000 with the Lorraine chipset in July 1985, the delay gave Atari, with its ma
The C64 Direct-to-TV, called C64DTV for short, is a single-chip implementation of the Commodore 64 computer, contained in a joystick, with 30 built-in games. The design is similar to the Atari Classics 10-in-1 TV Game; the circuitry of the C64DTV was designed by Jeri Ellsworth, a computer chip designer who had designed the C-One. Tulip Computers licensed the rights to Ironstone Partners, which cooperated with DC Studios and Mammoth Toys in the development and marketing of the unit. QVC purchased the entire first production run of 250,000 units and sold 70,000 of them on the first day that they were offered. There exist multiple versions of the C64DTV. DTV1 comes with 2 MB ROM, it first appeared in late 2004 for the American/Canadian market. DTV2 is a revised version for the European and world markets and appeared in late 2005; the ROM has been replaced by flash memory in these devices. However, the DTV2/PAL version suffers from a manufacturing fault, which results in poor colour rendering. In the DTV3, a problem with the blitter was fixed.
Core circuity ASIC running at 32 MHz internally, implementing 6510 CPU, VIC-II, SID, CIA, PLA Casing/Connectors integrated in a joystick five additional buttons running from batteries only Composite video, monaural audio looks similar to a Competition Pro joystick Graphics NTSC reprogrammable palette with 4 bits of luma and 4 bits of chroma DTV2 and later: "chunky" 256 color mode, additional blitter for fast image transformation Sound no support for SID filters DTV2 and later: 8 bit digital sound, additional options for envelope generators Memory DTV1: 128 KB RAM, 2 MB ROM DTV2 and later: 2 MB RAM, 2 MB flash memory DMA engine for RAM/RAM and ROM/RAM transfers DTV2 and later: additional RAM access using bank switching and blitter CPU implementing a 6510 at 1 MHz DTV2 and later: Enhanced CPU The official games for the unit are a mix of Epyx and Hewson C64 games. Games unique to the NTSC or PAL versions are noted below. Since the internal circuit board has exposed solder points for floppy-drive and keyboard ports, hardware modifications of the C64DTV are simple.
Known hardware mods keyboard connector external joystick floppy connector power unit connector fixing the palette problems of the PAL version S-Video connector user port Original C64 casing and PS2 keyboard Additional hardware Data transfer cable SD card interface 1541-III or MMC2IEC The internal flash memory is accessible as device 1. However, software is not included to support write operations. Flash devices used in the DTV are specified for a limited number of write accesses only; when using the standard keyboard mod, the F7 key does not work. There is a workaround, the "Keyboard Twister." The DTV contains software-flashable memory. A number of tools have been released to compile programs into DTV-compatible flash images and load it onto the DTV. People made their own game compilations, adding popular games that were not in the original DTV, added boot menus to make homebrew software development easier or enable new features, for example transfer programs like DTVtrans for transferring data from PC to DTV RAM and vice versa via the PC parallel port and the DTV joystick port.
DTV Hacking Wiki, archived from the original on 2013-04-14, retrieved 2013-08-06 - DTV versions overview, HOWTOs, DTV Programming guide The Official C64 DTV site - user manual plus some other information David Murray's Commodore DTV Hacking C64DTV stuff by tlr Flash Tool, ML-Monitor, PC<->DTV transfer system Mr. Latch-up's C64 DTV & Hummer Advice Column A page about the history of the device Details on fixing colour problem on PAL DTVs - Note that surface-mount soldering skills are required. DTVtrans, connecting a DTV to a PC via parallel port DTV2ser, connecting a DTV to a PC/Mac via USB or serial port Four ways to turn a C64 DTV into a C64 clone Grokk´s DTV Stuff DTVBIOS and DTVBASIC - make your DTV code-ready
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as "shells". Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, crustaceans such as crabs and lobsters; the shells of certain sponges and the various groups of shelled molluscs, including those of snails, tusk shells and nautilus, are exoskeletons. Some animals, such as the tortoise, have both an exoskeleton. Exoskeletons contain rigid and resistant components that fulfill a set of functional roles in many animals including protection, sensing, support and acting as a barrier against desiccation in terrestrial organisms. Exoskeletons have a role in defense from pests and predators, in providing an attachment framework for musculature. Exoskeletons contain chitin. Ingrowths of the arthropod exoskeleton known as apodemes serve as attachment sites for muscles.
These structures are composed of chitin, are six times as strong and twice as stiff as vertebrate tendons. Similar to tendons, apodemes can stretch to store elastic energy for jumping, notably in locusts. Many different species produce exoskeletons. Bone, cartilage, or dentine turtles. Chitin forms the exoskeleton in arthropods including insects, arachnids such as spiders, crustaceans such as crabs and lobsters, in some fungi and bacteria. Calcium carbonates constitute the shells of molluscs and some tube-building polychaete worms. Silica forms the exoskeleton in the microscopic diatoms and radiolaria. One species of mollusc, the scaly-foot gastropod makes use of the iron sulfides greigite and pyrite; some organisms, such as some foraminifera, agglutinate exoskeletons by sticking grains of sand and shell to their exterior. Contrary to a common misconception, echinoderms do not possess an exoskeleton, as their test is always contained within a layer of living tissue. Exoskeletons have evolved independently many times.
Further, other lineages have produced tough outer coatings analogous to an exoskeleton, such as some mammals. This coating is constructed from bone in the armadillo, hair in the pangolin; the armor of reptiles like turtles and dinosaurs like Ankylosaurs is constructed of bone. Since exoskeletons are rigid, they present some limits to growth. Organisms with open shells can grow by adding new material to the aperture of their shell, as is the case in snails and other molluscans. A true exoskeleton, like that found in arthropods, must be shed. A new exoskeleton is produced beneath the old one; as the old one is shed, the new skeleton is pliable. The animal will pump itself up to expand the new shell to maximal size let it harden; when the shell has set, the empty space inside the new skeleton can be filled up. Failure to shed the exoskeleton once outgrown can result in the animal being suffocated within its own shell, will stop subadults from reaching maturity, thus preventing them from reproducing.
This is the mechanism such as Azadirachtin. Exoskeletons, as hard parts of organisms, are useful in assisting preservation of organisms, whose soft parts rot before they can be fossilized. Mineralized exoskeletons can be preserved "as is", as shell fragments, for example; the possession of an exoskeleton permits a couple of other routes to fossilization. For instance, the tough layer can resist compaction, allowing a mold of the organism to be formed underneath the skeleton, which may decay. Alternatively, exceptional preservation may result in chitin being mineralized, as in the Burgess Shale, or transformed to the resistant polymer keratin, which can resist decay and be recovered. However, our dependence on fossilized skeletons significantly limits our understanding of evolution. Only the parts of organisms that were mineralized are preserved, such as the shells of molluscs, it helps that exoskeletons contain "muscle scars", marks where muscles have been attached to the exoskeleton, which may allow the reconstruction of much of an organism's internal parts from its exoskeleton alone.
The most significant limitation is that, although there are 30-plus phyla of living animals, two-thirds of these phyla have never been found as fossils, because most animal species are soft-bodied and decay before they can become fossilized. Mineralized skeletons first appear in the fossil record shortly before the base of the Cambrian period, 550 million years ago; the evolution of a mineralized exoskeleton is seen by some as a possible driving force of the Cambrian explosion of animal life, resulting in a diversification of predatory and defensive tactics. However, some Precambrian organisms produced tough outer shells while others, such as Cloudina, had a calcified exoskeleton; some Cloudina shells show evidence of predation, in the form of borings. On the whole, the fossil record only contains mineralised exoskeletons, since these are by far the most durable. Since most lineages with exoskeletons are thought to have started out with a non-mineralised exoskeleton which they mineralised, this makes it difficult to comment on the early evolution of each lineage's exoskeleton.
It is known, that in a short course of time, just before the Cambrian period, exoskeletons
The Commodore 64 known as the C64 or the CBM 64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 10 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the Commodore VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware; the C64 dominated the low-end computer market for most of the 1980s. For a substantial period, the C64 had between 30% and 40% share of the US market and two million units sold per year, outselling IBM PC compatibles, Apple computers, the Atari 8-bit family of computers. Sam Tramiel, a Atari president and the son of Commodore's founder, said in a 1989 interview, "When I was at Commodore we were building 400,000 C64s a month for a couple of years."
In the UK market, the C64 faced competition from the BBC Micro and the ZX Spectrum, but the C64 was still one of the two most popular computers in the UK. Part of the Commodore 64's success was its sale in regular retail stores instead of only electronics or computer hobbyist specialty stores. Commodore produced many of its parts in-house to control costs, including custom integrated circuit chips from MOS Technology, it has been compared to the Ford Model T automobile for its role in bringing a new technology to middle-class households via creative and affordable mass-production. 10,000 commercial software titles have been made for the Commodore 64 including development tools, office productivity applications, video games. C64 emulators allow anyone with a modern computer, or a compatible video game console, to run these programs today; the C64 is credited with popularizing the computer demoscene and is still used today by some computer hobbyists. In 2011, 17 years after it was taken off the market, research showed that brand recognition for the model was still at 87%.
In January 1981, MOS Technology, Inc. Commodore's integrated circuit design subsidiary, initiated a project to design the graphic and audio chips for a next generation video game console. Design work for the chips, named MOS Technology VIC-II and MOS Technology SID, was completed in November 1981. Commodore began a game console project that would use the new chips—called the Ultimax or the Commodore MAX Machine, engineered by Yash Terakura from Commodore Japan; this project was cancelled after just a few machines were manufactured for the Japanese market. At the same time, Robert "Bob" Russell and Robert "Bob" Yannes were critical of the current product line-up at Commodore, a continuation of the Commodore PET line aimed at business users. With the support of Al Charpentier and Charles Winterble, they proposed to Commodore CEO Jack Tramiel a true low-cost sequel to the VIC-20. Tramiel dictated. Although 64-Kbit dynamic random-access memory chips cost over US$100 at the time, he knew that DRAM prices were falling, would drop to an acceptable level before full production was reached.
The team was able to design the computer because, unlike most other home-computer companies, Commodore had its own semiconductor fab to produce test chips. The chips were complete by November, by which time Charpentier and Tramiel had decided to proceed with the new computer; the product was code named the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Yash Terakura, Shiraz Shivji, Bob Russell, Bob Yannes and David A. Ziembicki; the design and some sample software were finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends. The machine used the same case, same-sized motherboard, same Commodore BASIC 2.0 in ROM as the VIC-20. BASIC served as the user interface shell and was available on startup at the READY prompt; when the product was to be presented, the VIC-40 product was renamed C64. The C64 made an impressive debut at the January 1982 Consumer Electronics Show, as recalled by Production Engineer David A. Ziembicki: "All we saw at our booth were Atari people with their mouths dropping open, saying,'How can you do that for $595?'"
The answer was vertical integration. Commodore had a reputation for announcing products that never appeared, so sought to ship the C64. Production began in spring 1982 and volume shipments began in August; the C64 faced a wide range of competing home computers, but with a lower price and more flexible hardware, it outsold many of its competitors. In the United States the greatest competitors were the Atari 8-bit 400, the Atari 800, the Apple II; the Atari 400 and 800 had been designed to accommodate stringent FCC emissions requirements and so were expensive to
The Enterprise is a Zilog Z80-based home computer first produced in 1985. It was marketed by Enterprise Computers, its two variants are the Enterprise 64, with 64 kilobytes of Random Access Memory, the Enterprise 128, with 128 KB of RAM. The Enterprise has a 4 megahertz Z80 Central processing unit, 64 KB or 128 KB of RAM, 32 KB of internal read-only memory that contains the EXOS operating system and a screen editor / word processor; the BASIC programming language was supplied on a 16 KB ROM module. Two application-specific integrated circuit chips take some of the workload off of the central processor, they are named "Nick" and "Dave" after their designers, Nick Toop, who had worked on the Acorn Atom, Dave Woodfield. "Nick" manages graphics, while "Dave" handles memory paging. A bank switching scheme allows the memory to be expanded to a maximum of 4 megabytes; the highest 2 address lines from the Z80 are used to select one of the four 8-bit Page Registers in the Dave chip. The output from the selected register is used as the highest 8 bits of the 22-bit address bus, while the lowest 14 bits come directly from the Z80 address bus.
The 64 KB address space of the Z80 processor is divided into four 16k sections. Any 16k page from the 4 MB address space can be mapped to any of these sections; the lowest two pages of the 4 MB address space contain system ROM. The next four pages are reserved for a ROM cartridge; the top four pages are used as video RAM, but can be used for storage of program code and data as well. On the 128k model, the additional 64 KB of ram is mapped on pages 248 to 251; the remaining memory space can be used by external devices and memory modules connected to the expansion bus. The case is unusual in that it contains both a full-sized keyboard with programmable function keys, a joystick, its distinctive shape was due to the designers' desire to break away from customary designs. The low-profile keyboard is constructed with mechanical keycaps on top of a rubber membrane and has a standard layout, but the feel of the keys was disliked by many, or most people, because the keys weren't "full travel", but had a squishy feel, similar to a Sinclair QL or Spectrum+.
The joystick replaces the normal cursor keys, allows the cursor to be moved diagonally. Royal College of Art graduates Geoff Hollington and Nick Oakley were responsible for the design. Enterprise has five graphics modes: 40- and 80-column text modes, Lo-Res and Hi-Res bit mapped graphics, attribute graphics. Bit mapped graphics modes allow selection between displays of 2, 4,16 or 256 colours, but horizontal resolution decreases as colour depth increases. Interlaced and non-interlaced modes are available; the maximum resolution is 640 × 256 pixels non-interlaced. These resolutions permit only a 2-colour display. A 256-colour display has a maximum resolution of 80×256; the attribute graphics mode provides a 320×256 pixel resolution with 16 colours, selectable from a palette of 256. Multiple pages can be displayed on the screen if their graphics modes are different; each page has its own palette. The page height can be larger than the screen or the window it is displayed on; each page is connected to a channel of the EXOS operating system, so it is possible to write on a hidden page.
The sound is handled by the second ASIC chip, "Dave", has 3 sound channels plus a noise channel. Each channel's sound can be placed in the stereo image. Available effects include distortion, low-pass and high-pass filters, ring modulation; the chip has programmable envelope generators that are more flexible than synthesizers' traditional ADSR envelope, allow up to 255 phases to be specified for each envelope. On each phase, the envelope can adjust the sound's stereo balance; the Enterprise came included an array of connectors far beyond what was common on home computers of the time. There is an RGB output, a RS232 / RS423 serial port, a Centronics printer port, two external joystick ports, two cassette interfaces, a ROM cartridge slot, an ordinary expansion port. To save expense, many of the connectors did not use sockets, but instead had simple edge connectors that used the exposed traces at the edge of the printed circuit board; the BASIC ROM can be replaced by a ROM that emulates a ZX Spectrum, which theoretically allows the Enterprise to run the catalogue of thousands of Spectrum games.
An external floppy drive became available and allowed access to CP/M programs, while at the same time being compatible with the MS-DOS disc format and file structure. EXOS is contained in the system ROM, is based on "channels". All peripherals are accessed through channels, which allows the programs to treat all input and output devices identically; the system ROM contains a full-screen editor, which doubles as a simple word processor. It can edit BASIC programs, as well as programs written in other languages; the editor uses the joystick for cursor control. Enterprise does not include BASIC or any other programming language in its internal ROM, unlike most other home computers of the time, its BASIC interpreter was supplied on a 16k ROM cartridge, the language can be changed by switching the cartridge, a system similar to that of Acorn's BBC Micro. IS-Basic adheres to the ANSI BASIC standard, it is a structured language whose wide set of control structures includes multi-line IF... THEN
Shoot 'em up
Shoot'em up is a subgenre of the shooter genre of video games. There is no consensus as to; some restrict the definition to games featuring spacecraft and certain types of character movement. The genre's roots can be traced back to Spacewar!, one of the earliest computer games, developed in 1962. The shoot'em up genre was established by the hit arcade game Space Invaders, which popularised and set the general template for the genre in 1978, the genre was further developed by arcade hits such as Asteroids and Galaxian in 1979. Shoot'em ups were popular throughout early 1990s. In the mid-1990s, shoot'em ups became a niche genre based on design conventions established in the 1980s, catered to specialist enthusiasts in Japan. "Bullet hell" games are a subgenre that features overwhelming numbers of enemy projectiles in visually impressive formations. A "shoot'em up" known as a "shmup" or "STG", is a game in which the protagonist combats a large number of enemies by shooting at them while dodging their fire.
The controlling player must rely on reaction times to succeed. Beyond this, critics differ on which design elements constitute a shoot'em up; some restrict the genre to games using fixed or scrolling movement. Others widen the scope to include games featuring such protagonists as robots or humans on foot, as well as including games featuring "on-rails" and "run and gun" movement. Mark Wolf restricts the definition to games featuring multiple antagonists, calling games featuring one-on-one shooting "combat games". Critics described any game where the primary design element was shooting as a "shoot'em up", but shoot'em ups became a specific, inward-looking genre based on design conventions established in those shooting games of the 1980s. Shoot'em ups are a subgenre of shooter game, in turn a type of action game; these games are viewed from a top-down or side-view perspective, players must use ranged weapons to take action at a distance. The player's avatar is a vehicle under constant attack. Thus, the player's goal is to shoot as as possible at anything that moves or threatens them.
In some games, the player's character can withstand some damage. The main skills required in shoot'em ups are memorising enemy attack patterns; some games feature overwhelming numbers of enemy projectiles and the player has to memorise their patterns to survive. These games belong to one of the fastest-paced video game genres. Large numbers of enemy characters are featured; these enemies may behave in a certain way dependent on their type, or attack in formations that the player can learn to predict. The basic gameplay tends to be straightforward and many games offset this with boss battles and a variety of weapons. Shoot'em ups have realistic physics. Characters can change direction with no inertia, projectiles move in a straight line at constant speeds; the player's character can collect "power-ups" which may afford the character greater protection, an "extra life", or upgraded weaponry. Different weapons are suited to different enemies, but these games keep track of ammunition; as such, players tend to fire indiscriminately, their weapons only damage legitimate targets.
Shoot'em ups are categorized by design elements viewpoint and movement:Fixed shooters restrict the protagonist to a single axis of motion, enemies attack in a single direction, each level is contained within a single screen. Atari's Centipede is a hybrid, in that the player can move but that movement is constrained to a small area at the bottom of the screen, the game otherwise meets the fixed shooter definition. Tube shooters feature craft flying through an abstract tube, such as Gyruss. Rail shooters limit the player to moving around the screen. Examples include Space Harrier, Captain Skyhawk, Star Wars: Rebel Assault, Panzer Dragoon, Star Fox 64, Sin and Punishment. Light-Gun games that are "on-rails" are not in the shoot-em-up category but the FPS category, the term has been applied to scripted events in first-person shooters such as Call of Duty. Scrolling shooters include horizontal scrolling games. Vertically scrolling shooters: In a vertically scrolling shoot'em up, the action is viewed from above and scrolls up the screen.
Horizontally scrolling shooters: In a "horizontal shooter" or "side-scrolling shooter", the action is viewed side-on and scrolls horizontally. Isometrically scrolling shooters: A small number of scrolling shooters, such as Sega's Zaxxon, feature an isometric point of view. Multidirectional shooters feature 360 degree movement where the protagonist may rotate and move in any direction. Multidirectional shooters with one joystick for movement and one joystick for firing in any direction independent of movement are called "twin-stick shooters."Bullet hell is a shoot'em up in which the entire screen is almost fille
The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research. Referred to during development as the ZX81 Colour and ZX82, it was launched as the ZX Spectrum by Sinclair to highlight the machine's colour display, compared with the black and white of its predecessor, the ZX81; the Spectrum was released as eight different models, ranging from the entry level with 16 KB RAM released in 1982 to the ZX Spectrum +3 with 128 KB RAM and built in floppy disk drive in 1987. The Spectrum was among the first mainstream-audience home computers in the UK, similar in significance to the Commodore 64 in the US; the introduction of the ZX Spectrum led to a boom in companies producing software and hardware for the machine, the effects of which are still seen. Some credit it as the machine. Licensing deals and clones followed, earned Clive Sinclair a knighthood for "services to British industry"; the Commodore 64, Dragon 32, Oric-1, Oric Atmos, BBC Micro and the Amstrad CPC range were rivals to the Spectrum in the UK market during the early 1980s.
While the machine was discontinued in 1992, new software titles continue to be released – over 40 so far in 2018. The Spectrum is based on a Zilog Z80 A CPU running at 3.5 MHz. The original model has 16 KB of ROM and either 16 KB or 48 KB of RAM. Hardware design was by Richard Altwasser of Sinclair Research, the outward appearance was designed by Sinclair's industrial designer Rick Dickinson. Video output is through an RF modulator and was designed for use with contemporary television sets, for a simple colour graphic display. Text can be displayed using 32 columns × 24 rows of characters from the ZX Spectrum character set or from a set provided within an application, from a palette of 15 shades: seven colours at two levels of brightness each, plus black; the image resolution is 256×192 with the same colour limitations. To conserve memory, colour is stored separate from the pixel bitmap in a low resolution, 32×24 grid overlay, corresponding to the character cells. In practice, this means that all pixels of an 8x8 character block share one foreground colour and one background colour.
Altwasser received a patent for this design. An "attribute" consists of a foreground and a background colour, a brightness level and a flashing "flag" which, when set, causes the two colours to swap at regular intervals; this scheme leads to what was dubbed colour clash or attribute clash, where a desired colour of a specific pixel could not be selected. This became a distinctive feature of the Spectrum, meaning programs games, had to be designed around this limitation. Other machines available around the same time, for example the Amstrad CPC or the Commodore 64, did not suffer from this limitation; the Commodore 64 used colour attributes in a similar way, but a special multicolour mode, hardware sprites and hardware scrolling were used to avoid attribute clash. Sound output is through a beeper on the machine itself, capable of producing one channel with 10 octaves. Software was available that could play two channel sound; the machine includes an expansion bus edge connector and 3.5 mm audio in/out ports for the connection of a cassette recorder for loading and saving programs and data.
The "ear" port has a higher output than the "mic" and is recommended for headphones, with "mic" for attaching to other audio devices as line in. It was manufactured in Scotland, in the now closed Timex factory; the machine's Sinclair BASIC interpreter is stored in ROM and was written by Steve Vickers on contract from Nine Tiles Ltd. The Spectrum's chiclet keyboard is marked with BASIC keywords. For example, pressing "G" when in programming mode would insert the BASIC command GO TO; the BASIC interpreter was developed from that used on the ZX81 and a ZX81 BASIC program can be typed into a Spectrum unmodified, but Spectrum BASIC included many extra features making it easier to use. The ZX Spectrum character set was expanded from that of the ZX81, which did not feature lower-case letters. Spectrum BASIC included extra keywords for the more advanced display and sound, supported multi-statement lines; the cassette interface was much more advanced and loading around five times faster than the ZX81, unlike the ZX81, the Spectrum could maintain the TV display during tape storage and retrieval operations.
As well as being able to save programs, the Spectrum could save the contents of arrays, the contents of the screen memory, the contents of any defined range of memory addresses. Rick Dickinson came up with a number of designs for the "ZX82" project before the final ZX Spectrum design. A number of the keyboard legends changed during the design phase including ARC becoming CIRCLE, FORE becoming INK and BACK becoming PAPER; the Spectrum reused a number of design elements of the ZX81: The ROM code for things such as floating point calculations and expression parsing were similar. The simple keyboard decoding and cassette interfaces were nearly identical; the central ULA integrated circuit was somewhat similar although it implemented the major enhancement over the ZX81: A hardware based television raster generator that indirectly gave the new machine four times as much processing power as the ZX81 due to the Z80 now being released from this video generation task. A bug in the ULA as designed