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
A programmer, coder, or software engineer is a person who creates computer software. The term computer programmer can refer to a specialist in one area of computers, or to a generalist who writes code for many kinds of software. One who practices, or professes, a formal approach to programming may be known as a programmer analyst. On the other hand, "code monkey" is a derogatory term for a programmer who writes code without any involvement in the design or specifications. A programmer's primary computer language is prefixed to these titles, those who work in a web environment prefix their titles with web. A range of occupations—including: software developer, web developer, mobile applications developer, embedded firmware developer, software engineer, computer scientist, game programmer, game developer, or software analyst—that involve programming require a range of other skills; the use of the term programmer for these positions is sometimes considered an insulting or derogatory simplification.
British countess and mathematician Ada Lovelace is considered the first computer programmer, as she was the first to publish an algorithm intended for implementation on Charles Babbage's analytical engine, in October 1842, intended for the calculation of Bernoulli numbers. Because Babbage's machine was never completed to a functioning standard in her time, she never saw this algorithm run; the first person to run a program on a functioning modern electronically based computer was computer scientist Konrad Zuse, in 1941. The ENIAC programming team, consisting of Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman were the first working programmers. International Programmers' Day is celebrated annually on 7 January. In 2009, the government of Russia decreed a professional annual holiday known as Programmers' Day to be celebrated on 13 September, it had been an unofficial international holiday before that. The word "software" did not appear in print until the 1960s.
Before this time, computers were programmed either by customers, or the few commercial computer vendors of the time, such as UNIVAC and IBM. The first company founded to provide software products and services was Computer Usage Company in 1955; the software industry expanded in the early 1960s immediately after computers were first sold in mass-produced quantities. Universities and business customers created a demand for software. Many of these programs were written in-house by full-time staff programmers; some were distributed between users of a particular machine for no charge. Others were done on a commercial basis, other firms such as Computer Sciences Corporation started to grow; the computer/hardware makers started bundling operating systems, system software and programming environments with their machines. The industry expanded with the rise of the personal computer in the mid-1970s, which brought computing to the desktop of the office worker. In the following years, it created a growing market for games and utilities.
DOS, Microsoft's first operating system product, was the dominant operating system at the time. In the early years of the 21st century, another successful business model has arisen for hosted software, called software-as-a-service, or SaaS. From the point of view of producers of some proprietary software, SaaS reduces the concerns about unauthorized copying, since it can only be accessed through the Web, by definition, no client software is loaded onto the end user's PC. By 2014, the role of cloud developer had been defined. Computer programmers write, test and maintain the detailed instructions, called computer programs, that computers must follow to perform their functions. Programmers conceive and test logical structures for solving problems by computer. Many technical innovations in programming — advanced computing technologies and sophisticated new languages and programming tools — have redefined the role of a programmer and elevated much of the programming work done today. Job titles and descriptions may vary, depending on the organization.
Programmers work in many settings, including corporate information technology departments, big software companies, small service firms and government entities of all sizes. Many professional programmers work for consulting companies at client sites as contractors. Licensing is not required to work as a programmer, although professional certifications are held by programmers. Programming is considered a profession. Programmers' work varies depending on the type of business for which they are writing programs. For example, the instructions involved in updating financial records are different from those required to duplicate conditions on an aircraft for pilots training in a flight simulator. Simple programs can be written in a few hours, more complex ones may require more than a year of work, while others are never considered'complete' but rather are continuously improved as long as they stay in use. In most cases, several programmers work together as a team under a senior programmer’s supervision.
Programmers write programs according to the specifications determined b
The SAM Coupé is an 8-bit British home computer, first released in late 1989. It was designed to have compatibility with and is considered a clone of the Sinclair ZX Spectrum computer, since it features a compatible screen mode and emulated compatibility and was marketed as a logical upgrade from the Spectrum, it was manufactured by Miles Gordon Technology, based in Swansea in the United Kingdom. Released at a time when 16-bit home computers were more prevalent and a lack of commercial software titles led to it being a commercial failure, yet it had an active community of disk magazines and homebrew coders; the machine is based around a Z80B CPU clocked at 6 MHz and a 10,000-gate ASIC. The ASIC performs a similar role in the computer to the ULA in the ZX Spectrum; the Z80B CPU accesses selected parts of the large memory space in its 64 KB address space by slicing it into 16 KB banks and using I/O ports to select the particular blocks appearing in each 16 KB bank. The basic SAM Coupé model has 256 KB of RAM, upgradable internally to 512 KB via a connector on the main board accessible via a trapdoor underneath and externally using the Euroconnector with an additional 4 MB.
The computer has a direct connection for a cassette recorder for data storage but two 3.5 inch floppy disk drives can be installed within the case as well or externally using an interface. Six channels of 8-octave stereo sound are provided by a Philips SAA1099 sound generator chip; the ASIC includes a screen line interrupt, allowing video effects to be synchronised to specific display lines with little effort. The SAM Coupé provides four graphics modes: Mode 4 — 256×192, linear framebuffer, 4 bits per pixel = 24 KB Mode 3 — 512×192, linear framebuffer, 2 bits per pixel = 24 KB Mode 2 — 256×192, linear framebuffer, 1 bit per pixel with 32×192 separate attributes for each 8×1 block of pixels = 12 KB Mode 1 — 256×192, separate attributes, non-linear framebuffer arranged to match the display of the ZX Spectrum = 6.75 KBAll modes are paletted, with a 16-entry CLUT selecting from a palette of 128 colours. Palette entries consist of 2 bits for each of the red and blue components as well as an extra bit which increases the intensity of all three components.
The machine's non-standard SCART connector includes signals to drive a TTL-style monitor, in which case the total palette of colours is reduced to 16. In order to match the display speed of the ZX Spectrum, the Coupé introduces extra wait states to reduce the CPU speed while in Display Mode 1; the Motorola MC1377P RGB to PAL/NTSC encoder creates a composite video signal from the machine's RGB- and Sync-signals for the RF modulator. The machine shipped with 32 KB of ROM containing code to boot the machine and a BASIC interpreter written by Andrew Wright and influenced by his earlier Beta BASIC for the ZX Spectrum; the ROM's contained only the bootstrap code and the DOS was instead loaded from disk using the BOOT command, or the F9 key. The majority of disks shipped with SAMDOS, the system's first DOS, on them so that they could be directly booted. An improved replacement, MasterDOS, was developed offering faster disk access, more files and support for the real-time clock for filestamps amongst many other improvements.
The BASIC was advanced and included code for sprite drawing and basic vector shapes such as lines and circles. The screen co-ordinate system for these could be arbitrarily scaled and centered. A provision for "recording" sequences of graphics commands so that they could be repeated without the speed penalty of a BASIC interpreter in between was provided; the machine is capable of running CP/M 2.2 using the Pro-Dos software with support for both 720 Kilobyte format disks and IDE drives Internal RAM was shared between the video circuitry and the CPU, with CPU accesses incurring a speed penalty as it waited for ASIC accesses to finish. As a result, the SAM Coupé's CPU ran only around 14% faster than the ZX Spectrum CPU, yet was required to do much more work in SAM's high-resolution modes to produce a similar movement on the display. A Mode 3 or Mode 4 screen uses four times as much RAM as a ZX Spectrum, so four times the work had to be done in the same time. A small compensation was the straightforward arrangement of colour pixels in this memory, instead of the ZX Spectrum's more limited display and attributes memory.
Low-level graphics software operations could be much simpler than their Spectrum equivalents and therefore somewhat faster to execute. The penalty of memory contention delay applied to all memory accesses to RAM, not just to memory associated with the video circuitry. Hardware sprites and scrolling would have improved the performance of games there was insufficient wafer space on the VLSI ASIC to include such circuitry. While the main 256×192 area of the screen was being drawn, the processor could only access memory in 1 out of every 8 t-states. During the border area this was 1 out of every 4 t-states, which had no effect on the many instructions whose timings were a multiple of 4. In modes 3 and 4 the display could be disabled eliminating these memory contention delays for a full 6 MHz running speed. Code running in ROM was unaffected by the contention, though any RAM accesses they performed would still be affected; the SAM used Citizen 3.5 inch slimline drives which slotted in below the keyboard to provide front-facing slots.
Like IDE hard disks, these enclosures contained not just the drives but the drive controllers, a WD1772-02, with the effect that the SAM could use both drives simultan
Sweden the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, is connected to Denmark in the southwest by a bridge-tunnel across the Öresund, a strait at the Swedish-Danish border. At 450,295 square kilometres, Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. Sweden has a total population of 10.2 million. It has a low population density of 22 inhabitants per square kilometre; the highest concentration is in the southern half of the country. Germanic peoples have inhabited Sweden since prehistoric times, emerging into history as the Geats and Swedes and constituting the sea peoples known as the Norsemen. Southern Sweden is predominantly agricultural, while the north is forested. Sweden is part of the geographical area of Fennoscandia; the climate is in general mild for its northerly latitude due to significant maritime influence, that in spite of this still retains warm continental summers.
Today, the sovereign state of Sweden is a constitutional monarchy and parliamentary democracy, with a monarch as head of state, like its neighbour Norway. The capital city is Stockholm, the most populous city in the country. Legislative power is vested in the 349-member unicameral Riksdag. Executive power is exercised by the government chaired by the prime minister. Sweden is a unitary state divided into 21 counties and 290 municipalities. An independent Swedish state emerged during the early 12th century. After the Black Death in the middle of the 14th century killed about a third of the Scandinavian population, the Hanseatic League threatened Scandinavia's culture and languages; this led to the forming of the Scandinavian Kalmar Union in 1397, which Sweden left in 1523. When Sweden became involved in the Thirty Years War on the Reformist side, an expansion of its territories began and the Swedish Empire was formed; this became one of the great powers of Europe until the early 18th century. Swedish territories outside the Scandinavian Peninsula were lost during the 18th and 19th centuries, ending with the annexation of present-day Finland by Russia in 1809.
The last war in which Sweden was directly involved was in 1814, when Norway was militarily forced into personal union. Since Sweden has been at peace, maintaining an official policy of neutrality in foreign affairs; the union with Norway was peacefully dissolved in 1905. Sweden was formally neutral through both world wars and the Cold War, albeit Sweden has since 2009 moved towards cooperation with NATO. After the end of the Cold War, Sweden joined the European Union on 1 January 1995, but declined NATO membership, as well as Eurozone membership following a referendum, it is a member of the United Nations, the Nordic Council, the Council of Europe, the World Trade Organization and the Organisation for Economic Co-operation and Development. Sweden maintains a Nordic social welfare system that provides universal health care and tertiary education for its citizens, it has the world's eleventh-highest per capita income and ranks in numerous metrics of national performance, including quality of life, education, protection of civil liberties, economic competitiveness, equality and human development.
The name Sweden was loaned from Dutch in the 17th century to refer to Sweden as an emerging great power. Before Sweden's imperial expansion, Early Modern English used Swedeland. Sweden is derived through back-formation from Old English Swēoþēod, which meant "people of the Swedes"; this word is derived from Sweon/Sweonas. The Swedish name Sverige means "realm of the Swedes", excluding the Geats in Götaland. Variations of the name Sweden are used in most languages, with the exception of Danish and Norwegian using Sverige, Faroese Svøríki, Icelandic Svíþjóð, the more notable exception of some Finnic languages where Ruotsi and Rootsi are used, names considered as referring to the people from the coastal areas of Roslagen, who were known as the Rus', through them etymologically related to the English name for Russia; the etymology of Swedes, thus Sweden, is not agreed upon but may derive from Proto-Germanic Swihoniz meaning "one's own", referring to one's own Germanic tribe. Sweden's prehistory begins in the Allerød oscillation, a warm period around 12,000 BC, with Late Palaeolithic reindeer-hunting camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania.
This period was characterised by small bands of hunter-gatherer-fishers using flint technology. Sweden is first described in a written source in Germania by Tacitus in 98 AD. In Germania 44 and 45 he mentions the Swedes as a powerful tribe with ships that had a prow at each end. Which kings ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC; as for literacy in Sweden itself, the runic script was in use among the south Scandinavian elite by at least the 2nd century AD, but all that has come down to the present from the Roman Period is curt inscriptions on artefacts of male names, demonstrating th