1.
Tesla (Czechoslovak company)
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TESLA was a large, state-owned electrotechnical conglomerate in the former Czechoslovakia. The company was established as Elektra on 18 January 1921 and renamed TESLA on 7 March 1946, TESLA had a state-sponsored monopoly on electronics production in Czechoslovakia, and produced nearly all electronic products in the country until 1989. Many subsidiaries were created from the brand, including those at Liptovský Hrádok, Hradec Králové, Pardubice, Žďár nad Sázavou, Bratislava. Later, some of them were transformed into independent state-owned companies, while the companys wide range of production was impressive, quantity usually did not meet the needs of industrial customers. Many products gradually became obsolete simply because they were not updated, other products, e. g. some kinds of SCRs or Power-Transistors were competitive with the world market and so TESLA was the supplier for all eastern Europe Countries. Some high quality products were exported to western countries, for example the turntables NC470 or NC500 under the tradename Lenco. The most well-known international Tesla product was the Tesla 308U Talisman bakelite radio designed by Igor Didov of Tesla Bratislava, tESLAs logo is a rare sight in the present-day Czech Republic and Slovakia, as only a few of its subsidiaries have survived. One of its subsidiaries, the Slovak JJ Electronic in Čadca is known for its production of vacuum tubes
2.
Intel 8080
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The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, a slightly faster variant 8080A-1 became available later with clock frequency limit up to 3.125 MHz. The 8080 was successful enough that compatibility at the language level became a design requirement for the 8086 when design for it was started in 1976. This also means that the 8080 indirectly influenced the ubiquitous 32-bit and 64-bit x86 architectures of today, the Intel 8080 was the successor to the 8008. It used the basic instruction set and register model as the 8008. Every instruction in the 8008 has an equivalent instruction in the 8080, the 8080 also added a few 16-bit operations to its instruction set as well. Whereas the 8008 required the use of the HL register pair to indirectly access its 14-bit memory space, in addition, the internal 7-level push-down call stack of the 8008 was replaced by a dedicated 16-bit stack pointer register. The 8080s large 40-pin DIP packaging permitted it to provide a 16-bit address bus and it also has a 16-bit stack pointer to memory, and a 16-bit program counter. The processor maintains internal flag bits which indicates the results of arithmetic, conditional branch instructions test the various flag status bits. The flags can be copied as a group to the accumulator, the A accumulator and the flags together are called the PSW register or program status word. As with many other 8-bit processors, all instructions are encoded in a single byte, some of them are followed by one or two bytes of data, which can be an immediate operand, a memory address, or a port number. Like larger processors, it has automatic CALL and RET instructions for multi-level procedure calls and returns, there are also eight one-byte call instructions for subroutines located at the fixed addresses 00h, 08h, 10h. and 38h. These were intended to be supplied by external hardware in order to invoke a corresponding interrupt-service routine, the most sophisticated command is XTHL, which is used for exchanging the register pair HL with the value stored at the address indicated by the stack pointer. Most 8-bit operations can only be performed on the 8-bit accumulator, for 8-bit operations with two operands, the other operand can be either an immediate value, another 8-bit register, or a memory byte addressed by the 16-bit register pair HL. Direct copying is supported between any two 8-bit registers and between any 8-bit register and an HL-addressed memory byte, due to the regular encoding of the MOV instruction, there are redundant codes to copy a register into itself, which were of little use, except for delays. However, what would have been a copy from the HL-addressed cell into itself is used to encode the halt instruction. The XCHG instruction exchanges the values of the HL and DE register pairs, by adding HL to itself, it is possible to achieve the same result as a 16-bit arithmetical left shift with one instruction. The 8080 supported up to 256 input/output ports, accessed via dedicated I/O instructions—taking port addresses as operands and this I/O mapping scheme was regarded as an advantage, as it freed up the processors limited address space
3.
Hertz
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The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, megahertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is also used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is also used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels. Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch. Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
4.
Read-only memory
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Read-only memory is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, strictly, read-only memory refers to memory that is hard-wired, such as diode matrix and the later mask ROM, which cannot be changed after manufacture. Although discrete circuits can be altered in principle, integrated circuits cannot and that such memory can never be changed is a disadvantage in many applications, as bugs and security issues cannot be fixed, and new features cannot be added. More recently, ROM has come to include memory that is read-only in normal operation, the simplest type of solid-state ROM is as old as the semiconductor technology itself. Combinational logic gates can be joined manually to map n-bit address input onto arbitrary values of m-bit data output, with the invention of the integrated circuit came mask ROM. In mask ROM, the data is encoded in the circuit. This leads to a number of disadvantages, It is only economical to buy mask ROM in large quantities. The turnaround time between completing the design for a mask ROM and receiving the finished product is long, for the same reason, mask ROM is impractical for R&D work since designers frequently need to modify the contents of memory as they refine a design. If a product is shipped with faulty mask ROM, the way to fix it is to recall the product. Subsequent developments have addressed these shortcomings, PROM, invented in 1956, allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addressed problems 1 and 2 above, since a company can order a large batch of fresh PROM chips. The 1971 invention of EPROM essentially solved problem 3, since EPROM can be reset to its unprogrammed state by exposure to strong ultraviolet light. All of these technologies improved the flexibility of ROM, but at a significant cost-per-chip, rewriteable technologies were envisioned as replacements for mask ROM. The most recent development is NAND flash, also invented at Toshiba, as of 2007, NAND has partially achieved this goal by offering throughput comparable to hard disks, higher tolerance of physical shock, extreme miniaturization, and much lower power consumption. Every stored-program computer may use a form of storage to store the initial program that runs when the computer is powered on or otherwise begins execution. Likewise, every non-trivial computer needs some form of memory to record changes in its state as it executes. Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years. Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of storage such as magnetic disk drives were too costly
5.
Personal computer
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A personal computer is a multi-purpose electronic computer whose size, capabilities, and price make it feasible for individual use. PCs are intended to be operated directly by a end-user, rather than by an expert or technician. In the 2010s, PCs are typically connected to the Internet, allowing access to the World Wide Web, personal computers may be connected to a local area network, either by a cable or a wireless connection. In the 2010s, a PC may be, a multi-component desktop computer, designed for use in a location a laptop computer, designed for easy portability or a tablet computer. In the 2010s, PCs run using a system, such as Microsoft Windows, Linux. The very earliest microcomputers, equipped with a front panel, required hand-loading of a program to load programs from external storage. Before long, automatic booting from permanent read-only memory became universal, in the 2010s, users have access to a wide range of commercial software, free software and free and open-source software, which are provided in ready-to-run or ready-to-compile form. Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the computer market, first with MS-DOS. Alternatives to Microsofts Windows operating systems occupy a minority share of the industry and these include Apples OS X and free open-source Unix-like operating systems such as Linux and Berkeley Software Distribution. Advanced Micro Devices provides the alternative to Intels processors. PC is an initialism for personal computer, some PCs, including the OLPC XOs, are equipped with x86 or x64 processors but not designed to run Microsoft Windows. PC is used in contrast with Mac, an Apple Macintosh computer and this sense of the word is used in the Get a Mac advertisement campaign that ran between 2006 and 2009, as well as its rival, Im a PC campaign, that appeared in 2008. Since Apples transition to Intel processors starting 2005, all Macintosh computers are now PCs, the “brain” may one day come down to our level and help with our income-tax and book-keeping calculations. But this is speculation and there is no sign of it so far, in the history of computing there were many examples of computers designed to be used by one person, as opposed to terminals connected to mainframe computers. Using the narrow definition of operated by one person, the first personal computer was the ENIAC which became operational in 1946 and it did not meet further definitions of affordable or easy to use. An example of an early single-user computer was the LGP-30, created in 1956 by Stan Frankel and used for science and it came with a retail price of $47, 000—equivalent to about $414,000 today. Introduced at the 1965 New York Worlds Fair, the Programma 101 was a programmable calculator described in advertisements as a desktop computer. It was manufactured by the Italian company Olivetti and invented by the Italian engineer Pier Giorgio Perotto, the Soviet MIR series of computers was developed from 1965 to 1969 in a group headed by Victor Glushkov
6.
Czechoslovakia
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From 1939 to 1945, following its forced division and partial incorporation into Nazi Germany, the state did not de facto exist but its government-in-exile continued to operate. From 1948 to 1990, Czechoslovakia was part of the Soviet bloc with a command economy and its economic status was formalized in membership of Comecon from 1949, and its defense status in the Warsaw Pact of May 1955. A period of liberalization in 1968, known as the Prague Spring, was forcibly ended when the Soviet Union, assisted by several other Warsaw Pact countries. In 1993, Czechoslovakia split into the two states of the Czech Republic and Slovakia. Form of state 1918–1938, A democratic republic, 1938–1939, After annexation of Sudetenland by Nazi Germany in 1938, the region gradually turned into a state with loosened connections among the Czech, Slovak, and Ruthenian parts. A large strip of southern Slovakia and Carpatho-Ukraine was annexed by Hungary, 1939–1945, The region was split into the Protectorate of Bohemia and Moravia and the Slovak Republic. A government-in-exile continued to exist in London, supported by the United Kingdom, United States and its Allies, after the German invasion of Russia, Czechoslovakia adhered to the Declaration by United Nations and was a founding member of the United Nations. 1946–1948, The country was governed by a government with communist ministers, including the prime minister. Carpathian Ruthenia was ceded to the Soviet Union, 1948–1989, The country became a socialist state under Soviet domination with a centrally planned economy. In 1960, the country became a socialist republic, the Czechoslovak Socialist Republic. It was a state of the Soviet Union. 1989–1990, The federal republic consisted of the Czech Socialist Republic, 1990–1992, Following the Velvet Revolution, the state was renamed the Czech and Slovak Federal Republic, consisting of the Czech Republic and the Slovak Republic. Neighbours Austria 1918–1938, 1945–1992 Germany Hungary Poland Romania 1918–1938 Soviet Union 1945–1991 Ukraine 1991–1992 Topography The country was of irregular terrain. The western area was part of the north-central European uplands, the eastern region was composed of the northern reaches of the Carpathian Mountains and lands of the Danube River basin. Climate The weather is mild winters and mild summers, influenced by the Atlantic Ocean from the west, Baltic Sea from the north, and Mediterranean Sea from the south. The area was long a part of the Austro Hungarian Empire until the Empire collapsed at the end of World War I, the new state was founded by Tomáš Garrigue Masaryk, who served as its first president from 14 November 1918 to 14 December 1935. He was succeeded by his ally, Edvard Beneš. The roots of Czech nationalism go back to the 19th century, nationalism became a mass movement in the last half of the 19th century
7.
Slovakia
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Slovakia, officially the Slovak Republic, is a landlocked country in Central Europe. It is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east, Slovakias territory spans about 49,000 square kilometres and is mostly mountainous. The population is over 5 million and comprises mostly ethnic Slovaks, the capital and largest city is Bratislava. The Slavs arrived in the territory of present-day Slovakia in the 5th and 6th centuries, in the 7th century, they played a significant role in the creation of Samos Empire and in the 9th century established the Principality of Nitra. In the 10th century, the territory was integrated into the Kingdom of Hungary, which became part of the Habsburg Empire. After World War I and the dissolution of the Austro-Hungarian Empire, a separate Slovak Republic existed in World War II as a client state of Nazi Germany. In 1945, Czechoslovakia was reëstablished under Communist rule as a Soviet satellite, in 1989 the Velvet Revolution ended authoritarian Communist rule in Czechoslovakia. Slovakia became an independent state on 1 January 1993 after the dissolution of Czechoslovakia. The country maintains a combination of economy with universal health care. The country joined the European Union in 2004 and the Eurozone on 1 January 2009, Slovakia is also a member of the Schengen Area, NATO, the United Nations, the OECD, the WTO, CERN, the OSCE, the Council of Europe and the Visegrád Group. The Slovak economy is one of the fastest growing economies in Europe and its legal tender, the Euro, is the worlds 2nd most traded currency. Although regional income inequality is high, 90% of citizens own their homes, in 2016, Slovak citizens had visa-free or visa-on-arrival access to 165 countries and territories, ranking the Slovak passport 11th in the world. Slovakia is the world’s biggest per-capita car producer with a total of 1,040,000 cars manufactured in the country in 2016 alone, the car industry represents 43 percent of Slovakia’s industrial output, and a quarter of its exports. Radiocarbon datingputs the oldest surviving archaeological artefacts from Slovakia – found near Nové Mesto nad Váhom – at 270,000 BC and these ancient tools, made by the Clactonian technique, bear witness to the ancient habitation of Slovakia. Other stone tools from the Middle Paleolithic era come from the Prévôt cave near Bojnice, the most important discovery from that era is a Neanderthal cranium, discovered near Gánovce, a village in northern Slovakia. The most well-known finds include the oldest female statue made of mammoth-bone, the statue was found in the 1940s in Moravany nad Váhom near Piešťany. Numerous necklaces made of shells from Cypraca thermophile gastropods of the Tertiary period have come from the sites of Zákovská, Podkovice, Hubina and these findings provide the most ancient evidence of commercial exchanges carried out between the Mediterranean and Central Europe. The Bronze Age in the territory of modern-day Slovakia went through three stages of development, stretching from 2000 to 800 BC
8.
IQ 151
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The IQ151 was a personal computer produced by ZPA Nový Bor in the former Czechoslovakia. It had a Tesla MHB8080A CPU /2 MHz,32 KB RAM,4 KB ROM, with video output and it was primarily used in Czech schools, while in Slovakia the PMD85 series were used instead. This computer was produced due to a lack of foreign currency with which to buy systems from the West. After the fall of Communism in 1989, production of the IQ151 was stopped since it was not competitive in terms of price, information about IQ151 at old-computers. com East-European Home-Computer, IQ151
9.
Currency
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A currency in the most specific use of the word refers to money in any form when in actual use or circulation as a medium of exchange, especially circulating banknotes and coins. A more general definition is that a currency is a system of money in common use, under this definition, US dollars, British pounds, Australian dollars, and European euros are examples of currency. These various currencies are recognized stores of value and are traded between nations in exchange markets, which determine the relative values of the different currencies. Currencies in this sense are defined by governments, and each type has limited boundaries of acceptance, other definitions of the term currency are discussed in their respective synonymous articles banknote, coin, and money. The latter definition, pertaining to the systems of nations, is the topic of this article. Currencies can be classified into two systems, fiat money and commodity money, depending on what guarantees the value. Some currencies are legal tender in certain jurisdictions, which means they cannot be refused as payment for debt. Others are simply traded for their economic value, digital currency has arisen with the popularity of computers and the Internet. Currency evolved from two basic innovations, both of which had occurred by 2000 BC, originally money was a form of receipt, representing grain stored in temple granaries in Sumer in ancient Mesopotamia, then Ancient Egypt. In this first stage of currency, metals were used as symbols to represent value stored in the form of commodities and this formed the basis of trade in the Fertile Crescent for over 1500 years. Trade could only reach as far as the credibility of that military and it is not known what was used as a currency for these exchanges, but it is thought that ox-hide shaped ingots of copper, produced in Cyprus, may have functioned as a currency. It is thought that the increase in piracy and raiding associated with the Bronze Age collapse, possibly produced by the Peoples of the Sea, brought the trading system of oxhide ingots to an end. In Africa, many forms of value store have been used, including beads, ingots, ivory, various forms of weapons, livestock, the manilla currency, the manilla rings of West Africa were one of the currencies used from the 15th century onwards to sell slaves. African currency is still notable for its variety, and in many various forms of barter still apply. These factors led to the metal itself being the store of value, first silver, now we have copper coins and other non-precious metals as coins. Metals were mined, weighed, and stamped into coins and this was to assure the individual taking the coin that he was getting a certain known weight of precious metal. Coins could be counterfeited, but they created a new unit of account. Most major economies using coinage had several tiers of coins, using a mix of copper, silver, gold coins were used for large purchases, payment of the military and backing of state activities, they were more often used as measures of account than physical coins
10.
Western world
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The Western world or the West is a term usually referring to different nations, depending on the context, most often including at least part of Europe. There are many accepted definitions about what they all have in common, the Western world is also known as the Occident. The concept of the Western part of the earth has its roots in Greco-Roman civilization in Europe, before the Cold War era, the traditional Western viewpoint identified Western Civilization with the Western Christian countries and culture. Its political usage was changed by the antagonism during the Cold War in the mid-to-late 20th Century. The term originally had a literal geographic meaning, Western culture was influenced by many older great civilizations of the ancient Near East, such as Phoenicia, Minoan Crete, Sumer, Babylonia, and also Ancient Egypt. It originated in the Mediterranean basin and its vicinity, Greece, over time, their associated empires grew first to the east and west to include the rest of Mediterranean and Black Sea coastal areas, conquering and absorbing. Later, they expanded to the north of the Mediterranean Sea to include Western, Central, numerous times, this expansion was accompanied by Christian missionaries, who attempted to proselytize Christianity. There is debate among some as to whether Latin America is in a category of its own, specifically, Western culture may imply, a Biblical Christian cultural influence in spiritual thinking, customs and either ethic or moral traditions, around the Post-Classical Era and after. European cultural influences concerning artistic, musical, folkloric, ethic and oral traditions, the concept of Western culture is generally linked to the classical definition of the Western world. In this definition, Western culture is the set of literary, scientific, political, artistic, much of this set of traditions and knowledge is collected in the Western canon. The term has come to apply to countries whose history is marked by European immigration or settlement, such as the Americas, and Oceania. The geopolitical divisions in Europe that created a concept of East and West originated in the Roman Empire, Roman Catholic Western and Central Europe, as such, maintained a distinct identity particularly as it began to redevelop during the Renaissance. Even following the Protestant Reformation, Protestant Europe continued to see itself as more tied to Roman Catholic Europe than other parts of the civilized world. Use of the term West as a cultural and geopolitical term developed over the course of the Age of Exploration as Europe spread its culture to other parts of the world. Additionally, closer contacts between the West and Asia and other parts of the world in recent times have continued to cloud the use, herodotus considered the Persian Wars of the early 5th century BC a conflict of Europa versus Asia. The terms West and East were not used by any Greek author to describe that conflict, the Great Schism and the Fourth Crusade confirmed this deviation. The Renaissance in the West emerged partly from currents within the Roman Empire, Ancient Rome was a civilization that grew from a city-state founded on the Italian Peninsula about the 9th century BC to a massive empire straddling the Mediterranean Sea. In its 12-century existence, Roman civilization shifted from a monarchy, to a republic, nonetheless, despite its great legacy, a number of factors led to the eventual decline of the Roman Empire
11.
Velvet Revolution
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The Velvet Revolution or Gentle Revolution was a non-violent transition of power in what was then Czechoslovakia, occurring from November 17 to December 29,1989. Popular demonstrations against the one-party government of the Communist Party of Czechoslovakia combined students, the result was the end of 41 years of one-party rule in Czechoslovakia, and the subsequent dismantling of the planned economy and conversion to a parliamentary republic. On November 17,1989, riot police suppressed a student demonstration in Prague and that event sparked a series of demonstrations from November 19 to late December. By November 20, the number of protesters assembled in Prague grew from 200,000 the previous day to an estimated 500,000, a two-hour general strike involving all citizens of Czechoslovakia was held on November 27. On November 24, the top leadership of the Communist Party, including General Secretary Miloš Jakeš. Two days later, the legislature deleted the sections of the Constitution giving the Communists a monopoly of power. Barbed wire and other obstructions were removed from the border with West Germany, on December 10, President Gustáv Husák appointed the first largely non-communist government in Czechoslovakia since 1948, and resigned. Alexander Dubček was elected speaker of the parliament on December 28. In June 1990, Czechoslovakia held its first democratic elections since 1946, the term Velvet Revolution was coined by Rita Klímová, the dissidents English translator who later became the ambassador to the United States. The term was used internationally to describe the revolution, although the Czechs also used the term internally, after the dissolution of Czechoslovakia in 1993, Slovakia used the term Gentle Revolution, the term that Slovaks used for the revolution from the beginning. The Czech Republic continues to refer to the event as the Velvet Revolution, the Communist Party seized power on February 25,1948. No official opposition parties operated thereafter, dissidents published home-made periodicals, but they faced persecution by the secret police. Thus, the public did not openly support the dissidents for fear of dismissal from work or school. A writer or filmmaker could have his/her books or films banned for an attitude towards the socialist regime. These rules were easy to enforce, as all schools, media and they were under direct supervision and often were used as accusatory weapons against rivals. The nature of blacklisting changed gradually after the introduction of Mikhail Gorbachevs policies of Glasnost, the Czechoslovak Communist leadership verbally supported Perestroika, but made few changes. Speaking about the Prague Spring of 1968 was taboo, the first anti-government demonstrations occurred in 1988 and 1989, but these were dispersed and participants were repressed by the police. By the late 1980s, discontent with living standards and economic inadequacy gave way to support for economic reform
12.
Central processing unit
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The computer industry has used the term central processing unit at least since the early 1960s. The form, design and implementation of CPUs have changed over the course of their history, most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit chip. An IC that contains a CPU may also contain memory, peripheral interfaces, some computers employ a multi-core processor, which is a single chip containing two or more CPUs called cores, in that context, one can speak of such single chips as sockets. Array processors or vector processors have multiple processors that operate in parallel, there also exists the concept of virtual CPUs which are an abstraction of dynamical aggregated computational resources. Early computers such as the ENIAC had to be rewired to perform different tasks. Since the term CPU is generally defined as a device for software execution, the idea of a stored-program computer was already present in the design of J. Presper Eckert and John William Mauchlys ENIAC, but was initially omitted so that it could be finished sooner. On June 30,1945, before ENIAC was made, mathematician John von Neumann distributed the paper entitled First Draft of a Report on the EDVAC and it was the outline of a stored-program computer that would eventually be completed in August 1949. EDVAC was designed to perform a number of instructions of various types. Significantly, the programs written for EDVAC were to be stored in high-speed computer memory rather than specified by the wiring of the computer. This overcame a severe limitation of ENIAC, which was the considerable time, with von Neumanns design, the program that EDVAC ran could be changed simply by changing the contents of the memory. Early CPUs were custom designs used as part of a larger, however, this method of designing custom CPUs for a particular application has largely given way to the development of multi-purpose processors produced in large quantities. This standardization began in the era of discrete transistor mainframes and minicomputers and has accelerated with the popularization of the integrated circuit. The IC has allowed increasingly complex CPUs to be designed and manufactured to tolerances on the order of nanometers, both the miniaturization and standardization of CPUs have increased the presence of digital devices in modern life far beyond the limited application of dedicated computing machines. Modern microprocessors appear in electronic devices ranging from automobiles to cellphones, the so-called Harvard architecture of the Harvard Mark I, which was completed before EDVAC, also utilized a stored-program design using punched paper tape rather than electronic memory. Relays and vacuum tubes were used as switching elements, a useful computer requires thousands or tens of thousands of switching devices. The overall speed of a system is dependent on the speed of the switches, tube computers like EDVAC tended to average eight hours between failures, whereas relay computers like the Harvard Mark I failed very rarely. In the end, tube-based CPUs became dominant because the significant speed advantages afforded generally outweighed the reliability problems, most of these early synchronous CPUs ran at low clock rates compared to modern microelectronic designs. Clock signal frequencies ranging from 100 kHz to 4 MHz were very common at this time, the design complexity of CPUs increased as various technologies facilitated building smaller and more reliable electronic devices
13.
System monitor
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A system monitor is a hardware or software component used to monitor resources and performance in a computer system. Software monitors occur more commonly, sometimes as a part of a widget engine and these monitoring systems are often used to keep track of system resources, such as CPU usage and frequency, or the amount of free RAM. Other possible displays may include the date and time, system uptime, computer name, username, data, fan speeds, and the voltages being provided by the power supply. Less common are hardware-based systems monitoring similar information, customarily these occupy one or more drive bays on the front of the computer case, and either interface directly with the system hardware or connect to a software data-collection system via USB. With either approach to gathering data, the system displays information on a small LCD panel or on series of small analog or LED numeric displays. Some hardware-based system monitors also allow direct control of fan speeds, a few very high-end models of hardware system monitor are designed to interface with only a specific model of motherboard. These systems directly utilize the sensors built into the system, providing more detailed, single system, Distributed, I²C Network monitoring Mean time between failures Intelligent Platform Management Interface System profiler Monitoring a Linux System with X11/Console/Web-Based Tools
14.
Compact Cassette
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The Compact Cassette or Musicassette, also commonly called cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. It was released by Philips in 1962, having developed in Hasselt. Compact cassettes come in two forms, either already containing content as a cassette, or as a fully recordable blank cassette. Its uses ranged from portable audio to home recording to data storage for early microcomputers, the first cassette player designed for use in car dashes was introduced in 1968. Between the early 1970s and the early 2000s, the cassette was one of the two most common formats for prerecorded music, first alongside the LP record and later the compact disc. Compact Cassettes contain two miniature spools, between which a magnetically coated, polyester-type plastic film is passed and wound and these spools and their attendant parts are held inside a protective plastic shell. This reversal is achieved either by flipping the cassette, or by having the machine itself change the direction of tape movement. In 1935, decades before the introduction of the Compact Cassette, AEG released the first reel-to-reel tape recorder and it was based on the invention of the magnetic tape by Fritz Pfleumer, which used similar technology but with open reels. These instruments were expensive and relatively difficult to use and were therefore used mostly by professionals in radio stations. In 1958, following four years of development, RCA Victor introduced the stereo, quarter-inch, reversible, however, it was a large cassette, and offered few pre-recorded tapes. Despite the multiple versions, it failed, consumer use of tape only took off in the early 1960s, after playback machines reached a comfortable, user-friendly design. This was achieved primarily by the introduction of transistors which replaced the bulky, fragile, reel-to-reel tape then became more suitable to household use, but still remained an esoteric product. The team at Philips was led by Lou Ottens in Hasselt, Philips was competing with Telefunken and Grundig in a race to establish its cassette tape as the worldwide standard, and it wanted support from Japanese electronics manufacturers. However, the Philips Compact Cassette became dominant as a result of Philips decision to license the format free of charge, Philips also released the Norelco Carry-Corder 150 recorder/player in the US in November 1964. By 1966 over 250,000 recorders had been sold in the US alone, by 1968,85 manufacturers had sold over 2.4 million players. By the end of the 1960s, the business was worth an estimated 150 million dollars. In the early years sound quality was mediocre, but it improved dramatically by the early 1970s when it caught up with the quality of 8-track tape, the Compact Cassette went on to become a popular alternative to the 12-inch vinyl LP during the late 1970s. The mass production of blank Compact Cassettes began in 1964 in Hanover, prerecorded music cassettes were launched in Europe in late 1965
15.
Television
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Television or TV is a telecommunication medium used for transmitting moving images in monochrome, or in color, and in two or three dimensions and sound. The term can refer to a set, a television program. Television is a medium for entertainment, education, news, politics, gossip. Television became available in experimental forms in the late 1920s. After World War II, a form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses. During the 1950s, television was the medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US, for many reasons, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions greatly increased in popularity, another development was the move from standard-definition television to high-definition television, which provides a resolution that is substantially higher. HDTV may be transmitted in various formats, 1080p, 1080i, in 2013, 79% of the worlds households owned a television set. Most TV sets sold in the 2000s were flat-panel, mainly LEDs, major manufacturers announced the discontinuation of CRT, DLP, plasma, and even fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are gradually expected to be replaced by OLEDs, also, major manufacturers have announced that they will increasingly produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s, Television signals were initially distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by cable or optical fiber, satellite systems and. Until the early 2000s, these were transmitted as analog signals, a standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is correctly called a video monitor rather than a television, the word television comes from Ancient Greek τῆλε, meaning far, and Latin visio, meaning sight. The Anglicised version of the term is first attested in 1907 and it was. formed in English or borrowed from French télévision. In the 19th century and early 20th century, other. proposals for the name of a technology for sending pictures over distance were telephote. The abbreviation TV is from 1948, the use of the term to mean a television set dates from 1941
16.
Black and white
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Black and white, often abbreviated B/W or B&W, and hyphenated black-and-white when used as an adjective, is any of several monochrome forms in visual arts. Black-and-white images are not usually starkly contrasted black and white and they combine black and white in a continuum producing a range of shades of gray. Even when most studios had the capability to make color films they were not heavily utilized as using the Technicolor process was expensive, for the years 1940–1966, a separate Academy Award for Best Art Direction was given for black-and-white movies along with one for color. Television, Television program was first transmitted in black-and-white, scottish inventor John Logie Baird demonstrated the worlds first color television transmission on July 3,1928 using a mechanical process. Some color broadcasts in the US began in the 1950s, with color becoming common in industrialized nations during the late 1960s. In the United States, the Federal Communications Commission settled on a color NTSC standard in 1953, color television became more widespread in the U. S. between 1963 and 1967, when the CBS and ABC networks joined NBC in broadcasting full color schedules. Canada began airing color television in 1966 while the United Kingdom began to use a different color system from July 1967 known as PAL. The Republic Of Ireland followed in 1970, in China, black and white television sets were the norm until as late as the 1990s, color TVs not outselling them until about 1989. While seldom used now, many consumer camcorders have the ability to record in black-and-white. Photography, Photographs were either black-and-white or shades of sepia, color photography was originally rare and expensive and again often containing inaccurate hues. Color photography became more common from the mid-20th century, Today, black-and-white is a niche market for photographers who use the medium for artistic purposes. This can take the form of film or digital conversion to grayscale. For amateur use certain companies such as Kodak manufactured black-and-white disposable cameras until 2009, also, certain films are produced today which give black-and-white images using the ubiquitous C41 color process. Printing press, Most American newspapers were black-and-white until the early 1980s, The New York Times, some claim that USA Today was the major impetus for the change to color. In the UK, color was only introduced from the mid-1980s. Even today, many newspapers restrict color photographs to the front, similarly, daily comic strips in newspapers were traditionally black-and-white with color reserved for Sunday strips. Sometimes color is reserved for the cover, magazines such as Jet magazine were either all or mostly black-and-white until the end of the 2000s when it became all-color. Manga are typically published in black-and-white although now it is part of its image, many school yearbooks are still entirely or mostly in black-and-white
17.
PAL
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Phase Alternating Line is a colour encoding system for analogue television used in broadcast television systems in most countries broadcasting at 625-line /50 field per second. Other common colour encoding systems are NTSC and SECAM, all the countries using PAL are currently in process of conversion or have already converted standards to DVB, ISDB or DTMB. This page primarily discusses the PAL colour encoding system, the articles on broadcast television systems and analogue television further describe frame rates, image resolution and audio modulation. To overcome NTSCs shortcomings, alternative standards were devised, resulting in the development of the PAL, the goal was to provide a colour TV standard for the European picture frequency of 50 fields per second, and finding a way to eliminate the problems with NTSC. PAL was developed by Walter Bruch at Telefunken in Hannover, Germany, with important input from Dr. Kruse, the format was patented by Telefunken in 1962, citing Bruch as inventor, and unveiled to members of the European Broadcasting Union on 3 January 1963. When asked, why the system was named PAL and not Bruch the inventor answered that a Bruch system would not have sold very well. The first broadcasts began in the United Kingdom in June 1967, the one BBC channel initially using the broadcast standard was BBC2, which had been the first UK TV service to introduce 625-lines in 1964. Telefunken PALcolor 708T was the first PAL commercial TV set and it was followed by Loewe-Farbfernseher S920 & F900. Telefunken was later bought by the French electronics manufacturer Thomson, Thomson also bought the Compagnie Générale de Télévision where Henri de France developed SECAM, the first European Standard for colour television. The term PAL was often used informally and somewhat imprecisely to refer to the 625-line/50 Hz television system in general, accordingly, DVDs were labelled as PAL or NTSC even though technically the discs do not carry either PAL or NTSC composite signal. CCIR 625/50 and EIA 525/60 are the names for these standards, PAL. Both the PAL and the NTSC system use a quadrature amplitude modulated subcarrier carrying the chrominance information added to the video signal to form a composite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL and NTSC4.43, the SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers 4.25000 and 4.40625 MHz. Early PAL receivers relied on the eye to do that cancelling, however. The effect is that phase errors result in changes, which are less objectionable than the equivalent hue changes of NTSC. In any case, NTSC, PAL, and SECAM all have chrominance bandwidth reduced greatly compared to the luminance signal. The 4.43361875 MHz frequency of the carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency is 15625 Hz, the carrier frequency calculates as follows,4.43361875 MHz =283.75 ×15625 Hz +25 Hz
18.
Component video
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Component video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video in all the video information is combined into a single line level signal that is used in analog television. Like composite, component-video cables do not carry audio and are paired with audio cables. When used without any qualifications the term component video usually refers to analog YPBPR component video with sync on luma. Reproducing a video signal on a device is a straightforward process complicated by the multitude of signal sources. DVD, VHS, computers and video game consoles all store, process and transmit video signals using different methods, one way of maintaining signal clarity is by separating the components of a video signal so that they do not interfere with each other. A signal separated in this way is called component video, S-Video, RGB and YPBPR signals comprise two or more separate signals, and thus are all component-video signals. In the past, for most consumer-level applications, analog component video was used, however, component video is capable of carrying various signals, such as 480i, 480p, 576i, 576p, 720p, 1080i, 1080p, 2160p and beyond. Many new high definition TVs support the use of component video up to their native resolution, most modern computers offer this signal via a VGA port. Many televisions, especially in Europe, utilize RGB via the SCART connector, all arcade games, other than early vector and black-and-white games, use RGB monitors. In addition to the red, green and blue color signals, sync on luma, where the Y signal from S-Video is used alongside the RGB signal only for the purposes of sync. Composite sync is common in the European SCART connection scheme, RGBS requires four wires – red, green, blue and sync. If separate cables are used, the cable is usually colored yellow or white. Separate sync is most common with VGA, used worldwide for analog computer monitors and this is sometimes known as RGBHV, as the horizontal and vertical synchronization pulses are sent in separate channels. If separate cables are used, the lines are usually yellow and white, yellow and black, or gray. Sync on Green is less common, and while some VGA monitors support it, sony is a big proponent of SoG, and most of their monitors use it. Like devices that use video or S-video, SoG devices require additional circuitry to remove the sync signal from the green line
19.
Display resolution
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The display resolution or display modes of a digital television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It is usually quoted as width × height, with the units in pixels, for example,1024 ×768 means the width is 1024 pixels and this example would normally be spoken as ten twenty-four by seven sixty-eight or ten twenty-four by seven six eight. A consequence of having a display is that, for multi-format video inputs. Note that for broadcast television standards the use of the word here is a misnomer. In digital measurement, the resolution would be given in pixels per inch. In analog measurement, if the screen is 10 inches high, in the case of television inputs, many manufacturers will take the input and zoom it out to overscan the display by as much as 5% so input resolution is not necessarily display resolution. The eyes perception of display resolution can be affected by a number of factors – see image resolution, one factor is the display screens rectangular shape, which is expressed as the ratio of the physical picture width to the physical picture height. This is known as the aspect ratio, a screens physical aspect ratio and the individual pixels aspect ratio may not necessarily be the same. An array of 1280 ×720 on a 16,9 display has square pixels, an example of pixel shape affecting resolution or perceived sharpness, displaying more information in a smaller area using a higher resolution makes the image much clearer or sharper. Most television display manufacturers overscan the pictures on their displays, so that the effective on-screen picture may be reduced from 720 ×576 to 680 ×550, the size of the invisible area somewhat depends on the display device. HD televisions do this as well, to a similar extent, Computer displays including projectors generally do not overscan although many models allow it. CRT displays tend to be underscanned in stock configurations, to compensate for the distortions at the corners. As of July 2002,1024 ×768 eXtended Graphics Array was the most common display resolution, many web sites and multimedia products were re-designed from the previous 800 ×600 format to the layouts optimized for 1024 ×768. The availability of inexpensive LCD monitors has made the 5,4 aspect ratio resolution of 1280 ×1024 more popular for desktop usage during the first decade of the 21st century. Many computer users including CAD users, graphic artists and video game players ran their computers at 1600 ×1200 resolution or higher such as 2048 ×1536 QXGA if they had the necessary equipment. A new more-than-HD resolution of 2560 ×1600 WQXGA was released in 30-inch LCD monitors in 2007, as of March 2012,1366 ×768 was the most common display resolution. In 2010, 27-inch LCD monitors with the 2560 × 1440-pixel resolution were released by manufacturers including Apple. Panels for professional environments, such as use and air traffic control
20.
Grayscale
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In photography and computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information. Images of this sort, also known as black-and-white, are composed exclusively of shades of gray, grayscale images are distinct from one-bit bi-tonal black-and-white images, which in the context of computer imaging are images with only two colors, black and white. Grayscale images have many shades of gray in between, but also they can be synthesized from a full color image, see the section about converting to grayscale. The intensity of a pixel is expressed within a range between a minimum and a maximum, inclusive. This range is represented in a way as a range from 0 and 1. This notation is used in papers, but this does not define what black or white is in terms of colorimetry. Another convention is to employ percentages, so the scale is then from 0% to 100%. This is used for an intuitive approach, but if only integer values are used, the range encompasses a total of only 101 intensities. Also, the notation is used in printing to denote how much ink is employed in halftoning. In computing, although the grayscale can be computed through rational numbers, image pixels are stored in binary, the precision provided by this format is barely sufficient to avoid visible banding artifacts, but very convenient for programming because a single pixel then occupies a single byte. Technical uses often require more levels, to full use of the sensor accuracy. Sixteen bits per sample is a convenient choice for such uses, the TIFF and the PNG image file formats support 16-bit grayscale natively, although browsers and many imaging programs tend to ignore the low order 8 bits of each pixel. No matter what pixel depth is used, the binary representations assume that 0 is black, a common strategy is to use the principles of photometry or, more broadly, colorimetry to match the luminance of the grayscale image to the luminance of the original color image. This also ensures that both images will have the absolute luminance, as can be measured in its SI units of candelas per square meter, in any given area of the image. Then, linear luminance is calculated as a sum of the three linear-intensity values. To encode grayscale intensity in linear RGB, each of the three primaries can be set to equal the calculated linear luminance Y, linear luminance typically needs to be gamma compressed to get back to a conventional non-linear representation. In practice, because the three components are then equal, it is only necessary to store these values once in sRGB-compatible image formats that support a single-channel representation. The ITU-R BT.709 standard used for HDTV developed by the ATSC uses different color coefficients, although these are numerically the same coefficients used in sRGB above, the effect is different because here they are being applied directly to gamma-compressed values
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Color
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Color or colour is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them and this reflection is governed by the objects physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, there may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a colours colorfulness). The photo-receptivity of the eyes of species also varies considerably from our own. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red, papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or simply color science and it includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its wavelength and its intensity, when the wavelength is within the visible spectrum, it is known as visible light. Most light sources emit light at different wavelengths, a sources spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, in each such class the members are called metamers of the color in question. The table at right shows approximate frequencies and wavelengths for various pure spectral colors, the wavelengths listed are as measured in air or vacuum. A common list identifies six main bands, red, orange, yellow, green, blue, Newtons conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Some objects not only light, but also transmit light or emit light themselves. This effect is known as color constancy, opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with roughly equal strength, they appear white, if they absorb all wavelengths, they appear black. Opaque objects that reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences
22.
Tape recorder
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In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include reel-to-reel tape deck and the cassette deck, the use of magnetic tape for sound recording originated around 1930. Magnetizable tape revolutionized both the radio broadcast and music recording industries and it gave artists and producers the power to record and re-record audio with minimal loss in quality as well as edit and rearrange recordings with ease. The alternative recording technologies of the era, transcription discs and wire recorders, since some early refinements improved the fidelity of the reproduced sound, magnetic tape has been the highest quality analog sound recording medium available. As of the first decade of the 21st century, analog magnetic tape has been replaced by digital recording technologies for consumer purposes. Some individuals and organizations developed innovative uses for magnetic wire recorders while others investigated variations of the technology, one particularly important variation was the application of an oxide powder to a long strip of paper. This German invention was the start of a string of innovations that have led to present day magnetic tape recordings. The earliest known audio tape recorder was a non-magnetic, non-electric version invented by Alexander Graham Bells Volta Laboratory and patented in 1886. It employed a 3⁄16-inch-wide strip of wax-covered paper that was coated by dipping it in a solution of beeswax and paraffin and then had one side scraped clean, the machine was of sturdy wood and metal construction, and hand-powered by means of a knob fastened to the flywheel. The tape was taken up on the other reel. The sharp recording stylus, actuated by a vibrating mica diaphragm, in playback mode, a dull, loosely mounted stylus, attached to a rubber diaphragm, carried the reproduced sounds through an ear tube to its listener. Both recording and playback heads, mounted alternately on the two posts, could be adjusted vertically so that several recordings could be cut on the same 3⁄16-inch-wide strip. While the machine was never developed commercially, it was an ancestor to the modern magnetic tape recorder which it resembled somewhat in design. The tapes and machine created by Bells associates, examined at one of the Smithsonian Institutions museums, became brittle, the machines playback head was also missing. Otherwise, with some reconditioning, they could be placed into working condition, during the recording process, the tape moved through a pair of electrodes which immediately imprinted the modulated sound signals as visible black stripes into the paper tapes surface. On 13 August 1931, Duston filed USPTO Patent Application #556,743 for Method Of And Apparatus For Electrically Recording And Reproducing Sound And Other Vibrations, and which was renewed in 1934. Magnetic recording was conceived as early as 1877 by the American engineer Oberlin Smith, Analog magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal
23.
Current loop
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In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time and they are also used to transmit controller outputs to the modulating field devices such as control valves. These loops have the advantages of simplicity and noise immunity, and have an international user. Various Automation Protocols may replace analog current loops, but 4-20 mA is still an industrial standard. In industrial process control, analog 4–20 mA current loops are used for electronic signalling. These loops are used both for carrying information from field instrumentation, and carrying control signals to the process modulating devices. The key advantages of the current loop are, The loop can often power the device, with power supplied by the controller. Many instrumentation manufacturers produce 4-20 mA sensors which are loop powered, the live or elevated zero of 4 mA allows powering of the device even with no process signal output from the field transmitter. The accuracy of the signal is not affected by voltage drop in the interconnecting wiring and it has high noise immunity as it is low impedance circuit usually through twisted pair conductors. It is self-monitoring, currents less than 3.8 mA or more than 20.5 mA are taken to indicate a fault and it can be carried over long cables up to the limit of the resistance for the voltage used. In line displays can be inserted and powered by the loop, easy conversion to voltage using a resistor. Loop powered I to P converters can convert the 4-20 mA signal to a 3-15 psi pneumatic output for control valves, field instrumentation measurements are such as pressure, temperature, level, flow, pH or other process variables. A current loop can also be used to control a valve positioner or other output actuator, since input terminals of instruments may have one side of the current loop input tied to the chassis ground, analog isolators may be required when connecting several instruments in series. The relationship between current value and process variable measurement is set by calibration, which assigns different ranges of engineering units to the span between 4 and 20 mA. The mapping between engineering units and current can be inverted, so that 4 mA represents the maximum and 20 mA the minimum, depending on the source of current for the loop, devices may be classified as active or passive. For example, a chart recorder may provide power to a pressure transmitter. The pressure transmitter modulates the current on the loop to send the signal to the strip chart recorder, another loop may contain two passive chart recorders, a passive pressure transmitter, and a 24 V battery. Note that a 4-wire instrument has a power supply separate from the current loop
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RS-232
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In telecommunications, RS-232 is a standard for serial communication transmission of data. It formally defines the signals connecting between a DTE such as a terminal, and a DCE, such as a modem. The RS-232 standard is used in computer serial ports. The standard defines the characteristics and timing of signals, the meaning of signals. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. An RS-232 serial port was once a feature of a personal computer, used for connections to modems, printers, mice, data storage, uninterruptible power supplies. However, RS-232 is hampered by low speed, large voltage swing. In modern personal computers, USB has displaced RS-232 from most of its peripheral interface roles, nevertheless, RS-232 devices are still used, especially in industrial machines, networking equipment, and scientific instruments. Interface mechanical characteristics, pluggable connectors and pin identification, functions of each circuit in the interface connector. Standard subsets of interface circuits for selected telecom applications, the standard does not define such elements as the character encoding, the framing of characters, transmission order of bits, or error detection protocols. The character format and transmission bit rate are set by the serial port hardware which may also contain circuits to convert the internal logic levels to RS-232 compatible signal levels. The standard does not define bit rates for transmission, except that it says it is intended for bit rates lower than 20,000 bits per second, RS-232 was first introduced in 1960 by the Electronic Industries Association as a Recommended Standard. The original DTEs were electromechanical teletypewriters, and the original DCEs were modems, when electronic terminals began to be used, they were often designed to be interchangeable with teletypewriters, and so supported RS-232. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices, the resulting common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. The lack of adherence to the standards produced a thriving industry of breakout boxes, patch boxes, test equipment, books, a common deviation from the standard was to drive the signals at a reduced voltage. Some manufacturers therefore built transmitters that supplied +5 V and −5 V, later personal computers started to make use of the standard so that they could connect to existing equipment. For many years, an RS-232-compatible port was a feature for serial communications, such as modem connections. It remained in use into the late 1990s
25.
BASIC
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BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use. In 1964, John G. Kemeny and Thomas E. Kurtz designed the original BASIC language at Dartmouth College in the U. S. state of New Hampshire and they wanted to enable students in fields other than science and mathematics to use computers. At the time, nearly all use of computers required writing custom software, versions of BASIC became widespread on microcomputers in the mid-1970s and 1980s. Microcomputers usually shipped with BASIC, often in the machines firmware, having an easy-to-learn language on these early personal computers allowed small business owners, professionals, hobbyists, and consultants to develop custom software on computers they could afford. In the 2010s, BASIC remains popular in many computing dialects and in new languages influenced by BASIC, before the mid-1960s, the only computers were huge mainframe computers. Users submitted jobs on punched cards or similar media to specialist computer operators, the computer stored these, then used a batch processing system to run this queue of jobs one after another, allowing very high levels of utilization of these expensive machines. As the performance of computing hardware rose through the 1960s, multi-processing was developed and this allowed a mix of batch jobs to be run together, but the real revolution was the development of time-sharing. The original BASIC language was released on May 1,1964 by John G. Kemeny and Thomas E. Kurtz, the acronym BASIC comes from the name of an unpublished paper by Thomas Kurtz. BASIC was designed to allow students to write computer programs for the Dartmouth Time-Sharing System. It was intended specifically for technical users who did not have or want the mathematical background previously expected. Being able to use a computer to support teaching and research was quite novel at the time, the language was based on FORTRAN II, with some influences from ALGOL60 and with additions to make it suitable for timesharing. Wanting use of the language to become widespread, its designers made the available free of charge. They also made it available to schools in the Hanover area. In the following years, as dialects of BASIC appeared, Kemeny. A version was a part of the Pick operating system from 1973 onward. During this period a number of computer games were written in BASIC. A number of these were collected by DEC employee David H. Ahl and he later collected a number of these into book form,101 BASIC Computer Games, published in 1973. During the same period, Ahl was involved in the creation of a computer for education use
26.
Assembly language
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Each assembly language is specific to a particular computer architecture. In contrast, most high-level programming languages are generally portable across multiple architectures, Assembly language may also be called symbolic machine code. Assembly language is converted into machine code by a utility program referred to as an assembler. The conversion process is referred to as assembly, or assembling the source code, Assembly time is the computational step where an assembler is run. Assembly language uses a mnemonic to represent each low-level machine instruction or opcode, typically also each architectural register, flag, depending on the architecture, these elements may also be combined for specific instructions or addressing modes using offsets or other data as well as fixed addresses. Many assemblers offer additional mechanisms to facilitate development, to control the assembly process. A macro assembler includes a facility so that assembly language text can be represented by a name. A cross assembler is an assembler that is run on a computer or operating system of a different type from the system on which the code is to run. Cross-assembling facilitates the development of programs for systems that do not have the resources to support software development, a microassembler is a program that helps prepare a microprogram, called firmware, to control the low level operation of a computer. A meta-assembler is a used in some circles for a program that accepts the syntactic and semantic description of an assembly language. An assembler program creates object code by translating combinations of mnemonics and syntax for operations and this representation typically includes an operation code as well as other control bits and data. The assembler also calculates constant expressions and resolves symbolic names for memory locations, the use of symbolic references is a key feature of assemblers, saving tedious calculations and manual address updates after program modifications. Most assemblers also include facilities for performing textual substitution – e. g. to generate common short sequences of instructions as inline. Some assemblers may also be able to some simple types of instruction set-specific optimizations. One concrete example of this may be the ubiquitous x86 assemblers from various vendors, most of them are able to perform jump-instruction replacements in any number of passes, on request. Like early programming languages such as Fortran, Algol, Cobol and Lisp, assemblers have been available since the 1950s, however, assemblers came first as they are far simpler to write than compilers for high-level languages. There may be several assemblers with different syntax for a particular CPU or instruction set architecture, despite different appearances, different syntactic forms generally generate the same numeric machine code, see further below. A single assembler may also have different modes in order to support variations in syntactic forms as well as their exact semantic interpretations, there are two types of assemblers based on how many passes through the source are needed to produce the executable program
27.
Programmer (hardware)
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For programming a device which is either inserted into a socket on top of the programmer, or the programmer is directly connected by an adapter to the circuit board. Afterwards the data is transferred from the programmer into the device by applying signals through the connecting pins, some devices have a serial interface for receiving the programming data. Other devices require the data on parallel pins, followed by a pulse with a higher voltage for programming the data into the device. Usually device programmers are connected to a computer through a printer connector. Early device programmers had the size of a box and a weight of up to 4 kg. These types of programmers can be used in service for maintenance or setup of machinery that contains programmable circuits. A challenge for device programmer manufacturers is the design of the pin drivers that are connected to the circuit to be programmed. Due to the many circuits, every pin driver must be able to apply different voltages in a range of 0.25 Volts, clock rates of up to 40 MHz. Modern programmers use an integrated circuit for the pin drivers. In the early days of computing, before terminal and graphical display devices and it usually consisted of switches and LEDs, where instructions had to be entered one by one by setting the switches in a series of on and off positions. The positions of the switches corresponded to computer instructions, similar to how language is used today. Such hardware programmers are almost never seen or used today, batronix Xeltek Hardware description language JTAG interface Conitec Data I/O Elnec DediProg Technology Co. Ltd
28.
IEEE-488
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IEEE488 is a short-range digital communications 8-bit parallel multi-master interface bus specification. IEEE488 was created as HP-IB and is commonly called GPIB and it has been the subject of several standards. Newer standards have largely replaced IEEE488 for computer use, in the late 1960s, Hewlett-Packard manufactured various automated test and measurement instruments, such as digital multimeters and logic analyzers. They developed the HP Interface Bus to enable easier interconnection between instruments and controllers, the bus was relatively easy to implement using the technology at the time, using a simple parallel bus and several individual control lines. For example, the HP59501 Power Supply Programmer and HP 59306A Relay Actuator were both relatively simple HP-IB peripherals implemented only in TTL, using no microprocessor, HP licensed the HP-IB patents for a nominal fee to other manufacturers. It became known as the General Purpose Interface Bus, and became a de facto standard for automated, as GPIB became popular, it was formalized by various standards organizations. In 1975, the IEEE standardized the bus as Standard Digital Interface for Programmable Instrumentation, IEEE488, the standard was revised in 1987, and redesignated as IEEE488.1. These standards formalized the mechanical, electrical, and basic protocol parameters of GPIB, in 1987, IEEE introduced Standard Codes, Formats, Protocols, and Common Commands, IEEE488.2. IEEE488.2 provided for basic syntax and format conventions, as well as device-independent commands, data structures, error protocols, and the like. IEEE488.2 built on IEEE488.1 without superseding it, while IEEE488.1 defined the hardware and IEEE488.2 defined the protocol, there was still no standard for instrument-specific commands. Commands to control the same class of instrument, e. g. multimeters, the United States Air Force, and later Hewlett-Packard, recognized this problem. In 1989, HP developed their TML language which was the forerunner to Standard Commands for Programmable Instrumentation, SCPI was introduced as an industry standard in 1990. SCPI added standard generic commands, and a series of instrument classes with corresponding class-specific commands, SCPI mandated the IEEE488.2 syntax, but allowed other physical transports. The IEC developed their own standards in parallel with the IEEE, with IEC 60625-1 and IEC 60625-2, national Instruments introduced a backward-compatible extension to IEEE488.1, originally known as HS-488. It increased the maximum rate to 8 Mbyte/s, although the rate decreases as more devices are connected to the bus. This was incorporated into the standard in 2003, over HPs objections. 1/IEC 60625-1, IEEE488 is an 8-bit, electrically parallel bus. The bus employs sixteen signal lines — eight used for data transfer. Every device on the bus has a unique 5-bit primary address, the standard allows up to 15 devices to share a single physical bus of up to 20 meters total cable length
29.
Intel 8255
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The i8255 was also used with the Intel 8085 and Intel 8086 and their descendants and found wide applicability in digital processing systems. It was later cloned by other manufacturers and it is available in 40-pin DIP and 44-pin PLCC packages. The 82C55 is a higher-speed CMOS version, the i8255 provides 24 parallel input/output lines, but the functionality of the i8255 is now mostly embedded in larger VLSI processing chips as a sub-function. The i8255 is still made and is used to expand micro controller input/output. The i8255 has a function to the MOS Technology 6522. All of these chips were available in a 40-pin DIL package. However, the MOS chips contains other functions besides pin I/O, furthermore, the MOS devices allow the direction of all their I/O pins to be individually programmed. The i8255 I/O pins have only four programmable direction bits, one for all of Port A, one for Port B, one for Port C, the 8255 is widely used in many microcomputer/microcontroller systems and home computers such as the SV-328 and all MSX models. The 8255 is used in the original IBM-PC, PC/XT, PC/jr and clones, the 8255 is also directly compatible with the Z-80, as well as many Intel processors. The i8255 gives a CPU or digital access to programmable parallel I/O. The 8255 has 24 input/output pins and these are divided into three 8-bit ports. Port A and port B can be used as 8-bit input/output ports, Port C can be used as an 8-bit input/output port or as two 4-bit input/output ports or to produce handshake signals for ports A and B. The three ports are further grouped as follows, Group A consisting of port A and upper part of port C, Group B consisting of port B and lower part of port C. Eight data lines are available to read/write data into the ports or control register under the status of the ¬ RD and ¬ WR, which are active-low signals for read and write operations respectively. Address lines A1 and A0 allow to access a data register for each port or a register, as listed below. It is a signal, i. e. when ¬ CS =0. The RESET input is connected to the RESET line of system like 8085,8086, etc. so that when the system is reset and this is done to prevent 8255 and/or any peripheral connected to it from being destroyed due to mismatch of ports. As an example, consider an input device connected to 8255 at port A, the control register is an 8-bit register used to select the modes of operation and input/output designation of the ports
30.
White
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White is an achromatic color, a color without hue. An incoming light to the eye that stimulates all its three types of color sensitive cone cells in nearly equal amounts results in white. White is one of the most common colors in nature, the color of sunlight, snow, milk, chalk, limestone, in many cultures white represents or signifies purity, innocence, and light, and is the symbolic opposite of black, or darkness. According to surveys in Europe and the United States, white is the color most often associated with perfection, the good, honesty, cleanliness, the beginning, the new, neutrality, and exactitude. In ancient Egypt and ancient Rome, priestesses wore white as a symbol of purity, in the Middle Ages and Renaissance a white unicorn symbolized chastity, and a white lamb sacrifice and purity, the widows of kings dressed in white rather than black as the color of mourning. It was also used in 20th century modern architecture as a symbol of modernity, simplicity. White is an important color for almost all world religions, the Pope, the head of the Roman Catholic Church, has worn white since 1566, as a symbol of purity and sacrifice. In Islam, and in the Shinto religion of Japan, it is worn by pilgrims, in Western cultures and in Japan, white is the most common color for wedding dresses, symbolizing purity and virginity. In many Asian cultures, white is also the color of mourning, the white color on television screens and computer monitors is created with the RGB color model by mixing red, green and blue light at equal intensities. The word white continues Old English hwīt, ultimately from a Common Germanic *χwītaz also reflected in OHG wîz, ON hvítr, the root is ultimately from Proto-Indo-European language *kwid-, surviving also in Sanskrit śveta to be white or bright and Slavonic světŭ light. The Icelandic word for white, hvítur, is derived from the Old Norse form of the word hvítr. Common Germanic also had the word *blankaz, borrowed into Late Latin as *blancus, the antonym of white is black. Some non-European languages have a variety of terms for white. The Inuit language has seven different words for seven different nuances of white, Japanese has six different words, depending upon brilliance or dullness, or if the color is inert or dynamic. White was one of the first colors used in art, the Lascaux Cave in France contains drawings of bulls and other animals drawn by paleolithic artists between 18,000 and 17,000 years ago. Paleolithic artists used calcite or chalk, they sometimes as a background, sometimes as a highlight, along with charcoal and red, in ancient Egypt, white was connected with the goddess Isis. The priests and priestesses of Isis dressed only in white linen, in Greece and other ancient civilizations, white was often associated with mothers milk. In Greek mythology, the chief god Zeus was nourished at the breast of the nymph Amalthea, in the Talmud, milk was one of four sacred substances, along with wine, honey, and the rose
31.
Grey
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Grey or gray is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is a color without color and this means that there are equal components of red, green, and blue. The variations in intensity of these colors uniformly produce different shades of grey and it is the color of a cloud-covered sky, of ash and of lead. The first recorded use of grey as a name in the English language was in AD700. Grey is the dominant spelling in European and Commonwealth English, although remained in common usage in the UK until the second half of the 20th century. Gray has been the preferred American spelling since approximately 1825, although grey is an accepted variant, in Europe and the United States, surveys show that grey is the color most commonly associated with neutrality, conformity, boredom, uncertainty, old age, indifference, and modesty. Only one percent of respondents chose it as their favorite color, Grey comes from the Middle English grai or grei, from the Anglo-Saxon graeg, and is related to the Dutch grauw and grijs and German grau. The first recorded use of grey as a name in the English language was in AD700. In antiquity and the Middle Ages, grey was the color of undyed wool, and thus was the color most commonly worn by peasants and the poor. It was also the color worn by monks of the Franciscan order, Cistercian Order, Franciscan monks in England and Scotland were commonly known as the Grey friars, and that name is now attached to many places in Great Britain. During the Renaissance and the Baroque, grey began to play an important role in fashion, Black became the most popular color of the nobility, particularly in Italy, France, and Spain, and grey and white were harmonious with it. Grey was also used for the drawing of oil paintings. The painting would first be composed in grey and white, and then the colors, made with thin transparent glazes, the grisaille beneath would provide the shading, visible through the layers of color. Sometimes the grisaille was simply left uncovered, giving the appearance of carved stone, Grey was a particularly good background color for gold and for skin tones. It became the most common background for the portraits of Rembrandt Van Rijn and for many of the paintings of El Greco, the palette of Rembrandt was composed almost entirely of somber colors. Over this he put a layer of glaze made of mixture of blue smalt, red ochre. Using these ingredients and many others, he made greys which had, according to art historian Philip Ball, the warm, dark and rich greys and browns served to emphasize the golden light on the faces in the paintings. Grey became a fashionable color in the 18th century, both for womens dresses and for mens waistcoats and coats
32.
Computer keyboard
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In computing, a computer keyboard is a typewriter-style device which uses an arrangement of buttons or keys to act as a mechanical lever or electronic switch. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the input device for computers. A keyboard typically has characters engraved or printed on the keys, however, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs, other keys or simultaneous key presses can produce actions or execute computer commands. In normal usage, the keyboard is used as a text entry interface to type text and numbers into a word processor, in a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses to the controlling software, Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is used to give commands to the operating system of a computer, such as Windows Control-Alt-Delete combination. A command-line interface is a type of user interface operated entirely through a keyboard and it was through such devices that modern computer keyboards inherited their layouts. Earlier models were developed separately by individuals such as Royal Earl House, earlier, Herman Hollerith developed the first keypunch devices, which soon evolved to include keys for text and number entry akin to normal typewriters by the 1930s. From the 1940s until the late 1960s, typewriters were the means of data entry. The keyboard remained the primary, most integrated computer peripheral well into the era of personal computing until the introduction of the mouse as a device in 1984. By this time, text-only user interfaces with sparse graphics gave way to comparatively graphics-rich icons on screen, One factor determining the size of a keyboard is the presence of duplicate keys, such as a separate numeric keyboard, for convenience. A keyboard with few keys is called a keypad, another factor determining the size of a keyboard is the size and spacing of the keys. Reduction is limited by the consideration that the keys must be large enough to be easily pressed by fingers. Alternatively a tool is used for pressing small keys, standard alphanumeric keyboards have keys that are on three-quarter inch centers, and have a key travel of at least 0.150 inches. Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include characters, punctuation symbols, numbers. The internationally common 102/104 key keyboards have a left shift key. Also the enter key is usually shaped differently, computer keyboards are similar to electric-typewriter keyboards but contain additional keys, such as the command or Windows keys
33.
Computer terminal
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A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system. The function of a terminal is confined to display and input of data, a terminal that depends on the host computer for its processing power is called a dumb terminal or thin client. A personal computer can run terminal emulator software that replicates the function of a terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system. The terminal of the first working programmable, fully automatic digital Turing-complete computer, the Z3, had a keyboard, early user terminals connected to computers were electromechanical teleprinters/teletypewriters, such as the Teletype Model 33 ASR, originally used for telegraphy or the Friden Flexowriter. Later printing terminals such as the DECwriter LA30 were developed, however printing terminals were limited by the speed at which paper could be printed, and for interactive use the paper record was unnecessary. The problem was that the amount of memory needed to store the information on a page of text was comparable to the memory in low end minicomputers then in use. Displaying the information at video speeds was also a challenge and the control logic took up a rack worth of pre-integrated circuit electronics. Another approach involved the use of the tube, a specialized CRT developed by Tektronix that retained information written on it without the need to refresh. The Datapoint 3300 from Computer Terminal Corporation was announced in 1967 and shipped in 1969 and it solved the memory space issue mentioned above by using a digital shift-register design, and using only 72 columns rather than the later more common choice of 80. Some type of blinking cursor that can be positioned, the term intelligent in this context dates from 1969. Notable examples include the IBM2250 and IBM2260, predecessors to the IBM3270, providing even more processing possibilities, workstations like the Televideo TS-800 could run CP/M-86, blurring the distinction between terminal and Personal Computer. Most terminals were connected to minicomputers or mainframe computers and often had a green or amber screen, typically terminals communicate with the computer via a serial port via a null modem cable, often using an EIA RS-232 or RS-422 or RS-423 or a current loop serial interface. In fact, the design for the Intel 8008 was originally conceived at Computer Terminal Corporation as the processor for the Datapoint 2200. While early IBM PCs had single color green screens, these screens were not terminals. The screen of a PC did not contain any character generation hardware, all signals and video formatting were generated by the video display card in the PC, or by the CPU. An IBM PC monitor, whether it was the monochrome display or the 16-color display, was technically much more similar to an analog TV set than to a terminal. With suitable software a PC could, however, emulate a terminal, the Data General One could be booted into terminal emulator mode from its ROM. Since the advent and subsequent popularization of the computer, few genuine hardware terminals are used to interface with computers today
34.
Cyrillic script
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The Cyrillic script /sᵻˈrɪlɪk/ is a writing system used for various alphabets across eastern Europe and north and central Asia. It is based on the Early Cyrillic, which was developed in the First Bulgarian Empire during the 9th century AD at the Preslav Literary School. As of 2011, around 252 million people in Eurasia use it as the alphabet for their national languages. With the accession of Bulgaria to the European Union on 1 January 2007, Cyrillic became the official script of the European Union, following the Latin script. Cyrillic is derived from the Greek uncial script, augmented by letters from the older Glagolitic alphabet and these additional letters were used for Old Church Slavonic sounds not found in Greek. The script is named in honor of the two Byzantine brothers, Saints Cyril and Methodius, who created the Glagolitic alphabet earlier on, modern scholars believe that Cyrillic was developed and formalized by early disciples of Cyril and Methodius. In the early 18th century the Cyrillic script used in Russia was heavily reformed by Peter the Great, the new form of letters became closer to the Latin alphabet, several archaic letters were removed and several letters were personally designed by Peter the Great. West European typography culture was also adopted, Cyrillic script spread throughout the East and South Slavic territories, being adopted for writing local languages, such as Old East Slavic. Its adaptation to local languages produced a number of Cyrillic alphabets, capital and lowercase letters were not distinguished in old manuscripts. Yeri was originally a ligature of Yer and I, iotation was indicated by ligatures formed with the letter І, Ꙗ, Ѥ, Ю, Ѩ, Ѭ. Sometimes different letters were used interchangeably, for example И = І = Ї, there were also commonly used ligatures like ѠТ = Ѿ. The letters also had values, based not on Cyrillic alphabetical order. The early Cyrillic alphabet is difficult to represent on computers, many of the letterforms differed from modern Cyrillic, varied a great deal in manuscripts, and changed over time. Few fonts include adequate glyphs to reproduce the alphabet, the Unicode 5.1 standard, released on 4 April 2008, greatly improves computer support for the early Cyrillic and the modern Church Slavonic language. In Microsoft Windows, Segoe UI is notable for having complete support for the archaic Cyrillic letters since Windows 8, the development of Cyrillic typography passed directly from the medieval stage to the late Baroque, without a Renaissance phase as in Western Europe. Late Medieval Cyrillic letters show a tendency to be very tall and narrow. Peter the Great, Czar of Russia, mandated the use of westernized letter forms in the early 18th century, over time, these were largely adopted in the other languages that use the script. The development of some Cyrillic computer typefaces from Latin ones has also contributed to the visual Latinization of Cyrillic type, Cyrillic uppercase and lowercase letter forms are not as differentiated as in Latin typography
35.
Checksum
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A checksum is a small-sized datum derived from a block of digital data for the purpose of detecting errors which may have been introduced during its transmission or storage. It is usually applied to an installation file after it is received from the download server, by themselves, checksums are often used to verify data integrity but are not relied upon to verify data authenticity. The actual procedure which yields the checksum from an input is called a checksum function or checksum algorithm. Depending on its goals, a good checksum algorithm will usually output a significantly different value. Checksum functions are related to functions, fingerprints, randomization functions. However, each of those concepts has different applications and therefore different design goals, for instance a function returning the start of a string can provide a hash appropriate for some applications but will never be a suitable checksum. Checksums are used as cryptographic primitives in larger authentication algorithms, for cryptographic systems with these two specific design goals, see HMAC. Check digits and parity bits are special cases of checksums, appropriate for small blocks of data, some error-correcting codes are based on special checksums which not only detect common errors but also allow the original data to be recovered in certain cases. The simplest checksum algorithm is the so-called longitudinal parity check, which breaks the data into words with a number n of bits. The result is appended to the message as an extra word, with this checksum, any transmission error which flips a single bit of the message, or an odd number of bits, will be detected as an incorrect checksum. However, an error which affects two bits will not be detected if those bits lie at the position in two distinct words. Also swapping of two or more words will not be detected, if the affected bits are independently chosen at random, the probability of a two-bit error being undetected is 1/n. A variant of the algorithm is to add all the words as unsigned binary numbers, discarding any overflow bits. To validate a message, the receiver adds all the words in the manner, including the checksum, if the result is not a word full of zeros. This variant too detects any single-bit error, but the sum is used in SAE J1708. This feature generally increases the cost of computing the checksum, a message that is m bits long can be viewed as a corner of the m-dimensional hypercube. The effect of an algorithm that yields an n-bit checksum is to map each m-bit message to a corner of a larger hypercube. The 2m+n corners of this hypercube represent all possible received messages, the valid received messages comprise a smaller set, with only 2m corners
36.
Relocation (computer science)
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Relocation is the process of assigning load addresses to position-dependent code of a program and adjusting the code and data in the program to reflect the assigned addresses. Relocation is typically done by the linker at link time, but it can also be done at run time by a relocating loader, some architectures avoid relocation entirely by deferring address assignment to run time, this is known as zero address arithmetic. Object files are segmented into various memory segments types, example segments include code segments, data segments, stack segments, or others. The relocation table is a list of pointers created by the compiler or assembler and stored in the object or executable file. Each entry in the table, or fixup, is a pointer to an address in the object code that must be changed when the loader relocates the program so that it will refer to the correct location. Fixups are designed to support relocation of the program as a complete unit, in some cases, each fixup in the table is itself relative to a base address of zero, so the fixups themselves must be changed as the loader moves through the table. In some architectures a fixup that crosses certain boundaries or that is not aligned on a boundary is illegal. Instead, segments are relative values in the DOS EXE file and these segments need to be corrected, when the executable has been loaded into memory. The EXE loader uses a table to find the segments which need to be adjusted. When running native 64-bit binaries on Windows Vista and above, ASLR is mandatory, the Executable and Linkable Format executable format and shared library format used by most Unix-like systems allows several types of relocation to be defined. The following example uses Donald Knuths MIX architecture and MIXAL assembly language, the principles are the same for any architecture, though the details will change. Program SUBR is compiled to produce object file, shown as both code and assembler. The compiler may start the compiled code at an arbitrary location, location 13 contains the machine code for the jump instruction to statement ST in location 5. If SUBR is later linked with other code it may be stored at an other than zero. In this example the linker places it at location 120, the address in the jump instruction, which is now at location 133, must be relocated to point to the new location of the code for statement ST, now 125. When the program is loaded into memory to run it may be loaded at some other than the one assigned by the linker. This example shows SUBR now at location 300, the address in the jump instruction, now at 313, needs to be relocated again so that it points to the updated location of ST,305. Linker Library Object file Prebinding Static library Self-relocation Position-independent code Rebasing
37.
Didaktik
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The Didaktik was a series of home computers based on the clones of Intel 8080 and Zilog Z80 processors produced in former Czechoslovakia. Didaktik Alfa was produced in 1986, as a more professional clone of PMD85 and it featured 2.048 MHz Intel 8080 CPU,48 KB RAM,8 KB ROM with built-in BASIC, good keyboard, monitor video output with 288×256 resolutionwith four possible colours. Despite some changes in ROM, it was compatible with PMD85. Didaktik Alfa 1 was a clone of PMD 85-1, Didaktik Alfa 2 of PMD 85-2, Didaktik Beta was a slightly improved version of previous Didaktik Alfa, having almost identical hardware. While Didaktik Alfa and Beta were mostly deployed in schools, there was another production line and these were Sinclair ZX Spectrum 48K clones. This computer had become a dream for many children and adults in former socialist Czechoslovakia as the computer was considerably expensive. It is said there were waiting lists several years long, the design of the computer was very simple — just a grey or black box the size of A5 with flat plastic keyboard and connectors mounted on the rear side. All games developed for the ZX Spectrum 48K were generally compatible with this computer, there is no need to say that it established massive and flourishing black market with these games country-wide as they were officially unavailable behind the iron curtain. An audio cassette was used as the store and a TV served as the monitor. Gama 88 fixed the original ZX Spectrum bugs in a compatible way. The last and the best model was Gama 89 which fixed some more bugs, production of Didaktik Gama computers ceased in 1992. The next version, the Didaktik M introduced in 1990, was advanced in design. The machine resembled more of a home computer with arrow keys separated from the rest of the keyboard. Inside there was only 64 KB of total memory which was a disappointment in comparison to the Gama, a custom circuit from Russian company Angstrem was used instead of the original ULA as a result the screen had a square aspect ratio instead of a rectangle 4,3. In addition the whole RAM was realized by one set of 64 KB chips from which only 48 KB were used, there were two separated connectors for joysticks and one connector for additional interfaces, such as a printer interface. Unlike the previous version of Didaktik, these connectors were typical socialistic solution compatible with nothing that was available in the ČSSR. Thus, users were forced to develop and produce various and sometimes funny home-made interfaces to satisfy their needs, data storing and monitor type was the same as in the case of the Gama. Two floppy disk drives were developed and released later to offer the possibility of fast saving/loading of various programs,5. 25-inch floppy disk drive called D40 was introduced in 1992 and featured a Snapshot button that allowed to store current content of the memory on diskette
