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C++ C++ is a popular general purpose programming language. It is a compiled language and creates machine code for the specific machine hardware. This language is multi-paradigm and statistically typed free form. It is able to support procedural programming, object-orientation and data abstraction in addition to general programming. It was first developed in 1979 by Bjarne Stroustrup at Bell Labs as an enhancement to the C program language. It was named as ‘C with Classes’ and renamed C++ in 1983. It has enhancement classes with features such as function, name and operator overloading, templates, exception handling, virtual functions and multiple inheritance. Other features include references, constants, user-controlled free-store memory control, and improved type checking. Similar features from BCPL (B Computer Programming Language) such as the BCPL style single-line comments with two forward slashes (//). C++ was ratified in 1998 as ISO/IEC 14882:1998. Further developments continued with the current 2003 version, ISO/IEC 14882:2003 and a new version in development known informally as C++0x. Predecessors to C and C++ were APL (A Programming Language) and BCPL (B Computer Programming Language). Although APL was different in concept to C++, BCPL was similar in that it was used to create machine code. BCPL was more efficient than C. Advantages of C++ was that it was available for a larger variety of processors and platforms.  BCPL was very fast but was a low level programming language. C++ operates on both low-level and high-level programming. Inspiration for C++ came from features of Simula as programming language developed in the early 1960s. Its capacity for large software development was integrated into the development of C++. The Annotated C++ Reference Manual was published in 1990. As this programming language has evolved, so has the standard library. These included the stream I/O library which replaced C functions such as printf and scanf. In 2005, the Library Technical Report 1 (TR1) was released. This was not an official part of the standard but provides additional extensions to the original standard library. C++ is a royalty free programming language, although the standard document is not freely available. The key philosophies behind C++ are that it is designed to be a statically typed general purpose language that is efficient. It is able to support multiple programming styles and gives the programmer choices that are not platform specific.   Cache Cache is pronounced the same as ‘cash’. It is a collection of data that is duplicated within the cache and has its original data stored elsewhere. This temporary storage area holds frequently accessed data. This data can be accessed more quickly from reading the cache than re-fetching the data from its original location and expedites data access. The word ‘cache’ originated in 1967 from an article about memory improvement in the Model 85 to be published in the IBM Systems Journal. Lyle R Johnson, the Journal Editor, found the term ‘high-speed buffer’ undescriptive and suggested the term ‘cache’ (meaning ‘to hide’). The article was published in 1968 and the term ‘cache’ entered computer literature as a standard. The cache is a block of memory which is used for temporary data storage which is often required for retrieval. Both software and hardware have access to a cache. CPU’s (central processing unit) have used one or more caches since the 1980s. The CPU cache is managed by hardware. Other caches such as the page cache are managed by software. Fast local hard drives will use the operating system kernel to cache data. Accessing slower data storage devices such as tape drives or remote servers, a local hard drive will cache data to speed up data processing.  Hierarchical storage management is a technique which moves data between high speed and low speed storage media. This is the main concept behind cache. Caches are available for many computing activities. Web browsers recently visited websites using a cache. Using proxy caches, Internet Providers are able to save bandwidth on frequently accessed web pages. Search engines such as Google often provide a cache link next to search results to enable viewing web pages which may be temporarily unavailable from a web server. The cache is able to hold a quantity of data which can be increased. Each item of data is classified as an entry. The entries are a copy of the data held in a storage device. A tag is attached to each entry that identifies the data item in its original location. To access this data quickly, the device or software will first check the cache. In the event an entry is found with a corresponding tag of the required data, this entry will be accessed from the cache. This is called a cache hit. Alternatively, the cache may not hold the desired data and this is called a cache miss. In this event, the cache will fetch the data from the storage device and copy it into the cache for future access. If the cache is full, an entry which has been least recently used will be ejected from the cache to make room. The term buffer is sometimes confused with cache. The difference is that the buffer is temporary memory storage for one time use until the data has been transferred to another location or device.   CDMA Code division multiple access (CDMA) is a channel access method and should not be confused with now defunct CDMA mobile phone standard. A basic model of data communication is that several transmitters are able to send information at the same time over a single communication channel. This is called multiplexing and allows several users to share a bandwidth of frequencies. CDMA uses spread-spectrum technology. This technology generates energy in a specific bandwidth and it is intentionally spread in a frequency domain and results in a signal with a wider bandwidth. CDMA also uses a special coding scheme where each transmitter is assigned a code. It allows many users to multiplex over the same channel. Other technology such as TDMA (time division multiple access) and FDMA (frequency-division multiple access) use alternate methods. CDMA uses the spread-spectrum signalling with a modulated coded signal that is a lot higher data bandwidth than the actual data. One early application of CDMA is GPS (global positioning system). Before GPS, CDMA was initially a military technology and was used during World War II. Qualcomm created the communication chips for the CDMA technology and became privy to this classified technology. Once the technology became public, Qualcomm patented it and produced the technology commercially. The OmniTRACS satellite system uses CDMA for transportation of logistics. As bandwidth is a limited resource, the majority of modulation schemes try to minimize this signal. CDMA uses the spread spectrum technique and is able to use a greater transmission bandwidth. Initially, CDMA was used primarily for military applications such as guidance and communication systems. Spread spectrum ensured security and also a resistance to transmission jamming. CDMA is also effective in rejecting narrowband interference. This form of interference only affects a small portion of the spread spectrum signal and can be removed with minimal loss of information. The CDMA signal is also resistant to multipath fading as the signal occupies a large bandwidth. The loss of information by either of these instances is easily overcome and data recovered.   CGI The Common Gateway Interface (CGI) is a standard that interfaces external software applications with an information server or web server. The CGI standard originated in 1995 as part of a discussion between software and web site developers. The key contributors were Rob McCool (author of NCSA HTTP web server), John Franks (author of GN web server), Ari Luotonen (developer of CERN http web server), Tony Sanders (author of Plexus web server) and George Phillips (web server maintainer at University of British Columbia). The initial CGI specification was drafted by Rob McCool and it is still hosted by NCSA. A HTML document is retrieved by the web. It is a text file that does not change and is static. A CGI program is implemented in real time and it generates dynamic information as output. Executable applications commonly used with CGI commands include online database forms and email forms. The commands are embed in a HTML web page generate output to the web server. An information or web server responds to requests from web browsers. Depending upon the request, the server returns the appropriate outcome. The server will identify if a request is for a file stored on disk, if so, then it will retrieve that file. Alternatively, the request may identify an executable command. In this instance, the server will run the command and return the output. The CGI standard characterises the method of executing the command. The main drawback to the CGI standard was that is was low-tech. The command would call up a newly created process. This process would involve time to execute the command and would tie up memory in excess of the output generated. CGI that were called often had the potential to overwhelm web servers. Web servers usually contain a cgi-bin directory in the directory tree base that holds the executable files able to be called by the CGI standard. Development in web technologies has grown with many popular web servers developing their own extensions. These extensions allow third-party software to run inside the web server. A key example is web browsers such as Internet Explorer, Netscape or Mozilla Firefox’s plug-ins. These extension interfaces are not as standardized as CGI but are able to be implemented on multiple web servers. Another alternative is FastCGI, a CGI script accelerator. A CGI program is able to be written in any language – C++, Fortran, PERL, Unix shell, Visual Basic, or Apple Script. If a programming language such as C++ or Visual Basic is used to write the CGI program, the source code must be resident in the cgi-bin. Alternatively, if a scripting language is used such as PERL or Unix shell, then only the script needs to reside in the cgi-bin directory. CGI scripts are easier to debug or modify than a compiled program.   Chipset The chipset controls communication between the processor and external devices. It has an integral role in shaping system performance. It has a number of integrated circuits which are designed to perform related functions. An integrated circuit is a small electronic device and is manufactured from semiconductor material. Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductors developed the first integrated circuit in the 1950s. Dado Banato founded Chips and Technologies in the 1980s and pioneered the manufacture of chipsets for PC compatible computers. In the 1980s and 1990s, chipset referred to customized audio and graphics chips such as Commodore Amiga Original Chip Set or the SEGA System 16 chipset. Modern chipsets now replace the functions of one or more older chipsets. A chipset is a group of specialized chips that are designed to work together. They are commonly found on a computers motherboard or an expansion card. On the motherboard, the term chipset refers to a pair of chips that represent the north bridge and the south bridge. The north bridge associates the CPU with high speed devices such as graphics controllers and main memory. The south bridge links to lower speed peripheral buses (PCI or ISA) and on-chip integrated peripherals such as Ethernet, USB and audio devices. The chipset manufacturer is independent from the motherboard manufacturer. PC Compatible chipset manufacturers are Via Technologies, AMD, NVIDIA, Intel, Broadcom and SIS. Manufacturers for Apple and Unix include Sun, SGI and NeXT. Computer systems are able to share commonly used chipsets which are found in different computing specialties and operating system platforms. Any decisions regarding a computer system are reliant upon the chipset and CPU. The CPU is the brains of the computer and the chipset is its heart. The chipset controls the flow of information between the CPU and the system memory on the motherboard. The chipset is responsible for efficient data transfer and advanced power management to name a few. Chipsets are also integrated into modem and video cards. These chipsets differ in purpose but are of a similar principal in that they are integrated circuitry to perform a number of functions. AMD manufacture other chipsets for AMD processors such as the AMD 790FX, Intel processors ATI CrossFire Xpress 320 and Graphics processors such as ATI Radeon HD 3800. Intel manufacture chipsets for the Intel processors 975X for the dual core. NVIDIA produce chipsets for both AMD and Intel processors and graphic cards. SIS (Silicon Integrated Systems) and Via Technologies manufacture chipsets for both Intel and AMD processors.   Clock Speed The clock speed or clock rate is the rate of cycles per second in which a computer performs its basic operations. This rate is measured in hertz (Hz) and is a measurement of frequency. It is a basic unit of frequency in the International System of Units (SI) and is used worldwide for both computing and scientific situations. The hertz was named after Heinrich Hertz a German physicist, in honour of his scientific contributions to electromagnetism in 1930 by the International Electrotechnical Commision (IEC). In 1960, the General Conference on Weights and Measures (CGPM) adopted this term to replace the previous name of cycles per second (cps). By the 1970s, the term cycles per second was largely replaced by hertz. In computing and more specifically computer processing speed, the term gigahertz has become a common term. Clock speeds are stated in either megahertz (MHz) or gigahertz (GHz). One megahertz is equal to one million cycles per second. One gigahertz represents one billion cycles per second. The clock speed determines the rate or speed that a microprocessor executes instructions. All computers have an internal clock. This internal clock regulates the speed that instructions are carried out and will coordinate the individual computer components.  The CPU requires a specific number of clock cycles to undertake each instruction. The speed of the clock determines the number of instructions a CPU is able to execute per second. The clock is a quartz crystal. When electricity is passed through it, the clock vibrates at a specific frequency. The vibration emits a pulse or beat similar to a metronome. This pulse is sent to each component that is synchronized with it. The clock speed is able to coordinate and organise large amounts of data that is transmitted within the computer by the beat of the clock or clock cycle. Early computers had only one system clock. Advances in CPU technology created issues as other components could not process and send information at these increased speeds. Modern computers allow for asynchronous operation. Motherboards are able to have separate clocks for different components. Components such as video, system bus and expansion bus will have their own separate clock in addition to the CPU’s clock. Their individual clocks are able to optimize transfer rates and data exchange. CPU manufacturers will determine the clock rate of a CPU by testing at the end of the manufacturing process. Each CPU is labelled as complying with a set of standards such as 2.5 GHz clock rate.     CMOS Complementary metal-oxide-semiconductor (CMOS) is pronounced as “see-moss”. CMOS technology is a major class of integrated circuits which are used in microprocessors, static RAM (random access memory), microcontrollers, and other digital logic circuits. Analog circuits such as data converters, transceivers and image sensors also use CMOS technology. The patent for CMOS was obtained by Frank Wanlass in 1967 in the United States. Two significant features of CMOS are that it has low static power consumption and high noise immunity. The transistor only draws power when it switches between on or off. With minimal power usage, CMOS devices do generate low levels of waste heat. CMOS are composed of semiconductor materials such as silicon and germanium. Elements are added to the manufacturing process that increase its conductivity. This process is called doping. Common dopants are arsenic, antimony, bismuth and phosphorous. Depending on the type of dopant or level used will establish whether the semiconductor is N (NMOS) or P (PMOS) type. N-type is a current that is conducted by excess free electrons. P-type is a current that is conducted by electron vacancies. CMOS semiconductors have both NMOS and PMOS circuits. Only one of these circuit types is active at any time, which reduces the amount of power. Chips that use only one type of transistor require more power. This technology has proved popular with CMOS chips used in battery powered devices. The CMOS battery serves to hold CMOS memory such as date, time and system setup parameters in personal computers. There are four main types of CMOS batteries, external lithium, barrel style solder, PS2 6v and the coin cell. The most common type of battery is the Coin cell. It is the size of a coin and its small thin shape makes it ideal for use in computers. CMOS batteries have a standard lifetime of approximately 10 years, although this varies depending on the computers use and environment. Modern commercial CMOS products are integrated circuits that are composed of millions of transistors. It is a rectangular piece of silicon no more than 4 centimetres and is called a chip or CMOS chip.   Codec A Codec is a specialised program that is able to encode or decode a digital data stream or signal. It is an acronym for compression/decompression. The codec is able to reduce the amount of bytes that are used by large files or programs. There are many codec schemes. These are used to minimize file transfer times and are often used in conjunction with the Internet. Programs for the Internet such as QuickTime and NetMeeting use codecs. Other codecs are meant to maximize data that is to be stored in a CD-ROM or disk space. An endec is a similar concept that is used for hardware. Early codecs were hardware coded. They encoded analog signals into Pulse code modulation (PCM) and then decoded. The term codec is now applied to software that converts between digital signal formats. A codec is able to encode and decode. When encoding, the codec uses compression which eliminates redundancies in the data. Any file whether text, programs, images, video or audio can be compressed. Compression reduces the size of a file by a factor of 100. A 20 megabyte file may be reduced to 200 kilobytes. Decoding is when the codec uses decompression to ‘undo’ the compression. Videoconferencing and other streaming media applications use codecs extensively. The video camera uses an analog to digital converter (ADC) to convert signals from analogue to digital. These signals then pass through a video compressor for either transmission or storage. The signal is then run through a video decompressor in a receiving device. To display the file, the signal passes through a digital to analogue converter (DAC). This whole process or video conferencing unit is called a codec. Audio files follow the same process and these codecs are used in the sound cards of computers. The raw encoded structure of audio and video data is called essence. There are many codecs available with some available free for download and others at a cost. Often, multimedia data streams require both audio and video data as well as some metadata that will synchronize both the audio and video. A container is needed to handle these three streams as they will each use different programs or processes. They will be encapsulated within a container format. AVI is often mistaken to be a codec, but is actually a container format. Other popular containers are QuickTime, RealMedia, DivX and MP4. Links: http://www.free-codecs.com/   Contrast Ratio The contrast ratio refers to the ratio of the brightest (white) to the darkest (black) on a screen. The higher the number the darker the black is displayed. For example, 800:1 represents that the white pixels of the monitor is 800 times brighter than a perfectly black pixel. “Brightness is measured in nits. The average LCD currently is in the range of 250-280 nits. Ultra-bright models are capable of 450 nits. A higher nit level isn’t always good. In a darker room, 450 nits would make you reach for your sun glasses.” - Ahinc.com   CPU The CPU (Central Processing Unit) is also called a processor. A broad definition of CPU is that it is able to execute computer programs. It has its grounding in the early computers in the 1960s. The design and implementation of CPUs have considerably changed over the years, although their fundamental functions have remained constant. The introduction of the integrated circuit (IC) allowed for the miniaturization in the design of CPUs. Early CPUs were designed specifically for a particular computer and included a number of components and small integrated circuits on one or more circuit boards. This was costly as CPUs were not able to be used in different computer designs. Modern CPUs are used in personal computers, laptops, cell phones, toys, cars and robotics to name a few. The CPU is housed in a single chip called a microprocessor and usually has only one integrated circuit. The smaller size means a faster switching time and this is reflected in the overall speed of the CPU and since the 1970s, the microprocessor class of CPUs has eclipsed all other CPU implementations. The CPU is an internal component of the computer and in appearance are small, square and have a large number of metallic pins on the underside. To reduce heat emission a heat sink fan is attached on top of the CPU. It is inserted into a CPU socket with the pins facing down on the motherboard. The motherboard manufacturer’s specifications will determine the CPU requirements. A computers most important component is the CPU. The CPU is the brains of the computer. Its main function is to execute a program or a sequence of stored instructions. A CPU has two key components. The arithmetic logic unit (ALU) performs arithmetic and logical operations. The control unit (CU) is able to extract instructions from memory. Calling on the ALU when necessary, the CU decodes and executes the instructions. In operation, all CPUs undertake four key steps – fetch, decode, execute and writeback. The CPU will fetch from memory the instructions of what the CPU is required to do. The instruction is then broken up (decoded) into parts that are important to other areas of the CPU. The execute step brings together each part of the CPU to perform the instructed operation. In the writeback step, the CPU will ‘write back’ the results into either the internal CPU register or into the main memory.   CRT A cathode ray tube (CRT) is used in many devices such as televisions and computer monitors. It is a vacuum tube that contains an electron gun. A fluorescent screen is able to accelerate and deflect the electron beam. The CRT forms images by using the light emitted from the fluorescent screen. The images can take the form of electrical waveforms when the CRT is used in an oscilloscope or as pictures when used in television or computer monitors. German physicist, Ferdinand Braun invented the earliest CRT, known as a Braun Tube in 1897. The Braun CRT used a cold-cathode diode. In 1922 the first CRT using a hot cathode was developed by John Johnson and Harry Weinhart of Western Electric as a commercial product. The key component of a CRT is the electron gun. It produces an electron beam which is a stream of electrons that are focussed into a thin beam. The electron gun is located at the rear of the CRT and is connected by a circular array of connection pins at its end. The processing of the CRT’s single electron beam enables the display of moving pictures that appear in natural colours. CRTs are usually bowl shaped with the exception of a flat CRT which was incorporated by Sony in 1982. In the flat CRT unit, the electron gun is located below the display surface at right angles. Due to this change in placement of the electron gun, complex electronics were required to ensure an undistorted picture. The CRT is enclosed in an outer glass envelope and it has a dual function. It allows light to generate out of the computer monitor. The glass envelope is leaded as it must block dangerous x-rays. These x-rays are generated by the electrons impacting within the CRT face. Colour CRTs require higher voltages and with high voltages the amount of x-rays produced also increase. Modern CRTs incorporate the leaded glass, protective circuits and other shielding to ensure that x-ray emissions are within approved safety limits. CRT’s have been widely used in television and computer monitors up till 2007. Plasma and LCD screens have increased in popularity and have impacted directly on the CRT market share. Modern computer monitors and televisions predominantly utilise the LCD screen technology. Both Sony and Samsung no longer produce any CRT models. Sony discontinued production of CRT computer monitors and German manufacturer Loewe ceased manufacture of CRT TVs in 2005. Although LCD units do require less power for each display area, CRTs are still popular in computer gaming, printing and broadcasting industries and in many graphics fields. This is due to their superior colour reliability and contrast. CRTs have a better resolution when viewed from angles and in displaying moving images.   CRT (Cathode Ray Tube) Cathode Ray Tube (CRT) is a very common type of display unit. The technology behind CRT monitors is quite old and closely resembles a television. These monitors are fairly big and heavy and are slowly phasing out.