Computer architecture

Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit (CPU) performs internally and accesses addresses in memory.

It may also be defined as the science and art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals.

Assembly language

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPUarchitecture. This representation is usually defined by the hardware manufacturer, and is based on abbreviations (called mnemonics) that help the programmer remember individual instructions, registers, etc. An assembly language is thus specific to a certain physical or virtual computer architecture (as opposed to most high-level languages, which are usually portable).

Assembly languages were first developed in the 1950s, when they were referred to as second generation programming languages. They eliminated much of the error-prone and time-consuming first-generationprogramming needed with the earliest computers, freeing the programmer from tedium such as remembering numeric codes and calculating addresses. They were once widely used for all sorts of programming. However, by the 1980s (1990s on small computers), their use had largely been supplanted by high-level languages, in the search for improved programming productivity. Today, assembly language is used primarily for direct hardware manipulation, access to specialized processor instructions, or to address critical performance issues. Typical uses are device drivers, low-level embedded systems, andreal-time systems.

A utility program called an assembler is used to translate assembly language statements into the target computer's machine code. The assembler performs a more or less isomorphic translation (a one-to-one mapping) from mnemonic statements into machine instructions and data. (This is in contrast with high-level languages, in which a single statement generally results in many machine instructions.)

Many sophisticated assemblers offer additional mechanisms to facilitate program development, control the assembly process, and aid debugging. In particular, most modern assemblers (although many have been available for more than 40 years already) include a macro facility (described below), and are calledmacro assemblers.

MS-DOS

MS-DOS (short for Microsoft Disk Operating System) is an operating system commercialized by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the main operating system for personal computers during the 1980s. It was preceded by M-DOS(also call MIDAS), designed and copyrighted by Microsoft in 1979. MSDOS was based on the Intel 8086 family of microprocessors, particularly theIBM PC and compatibles. It was gradually replaced on consumer desktop computers by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system and Linux. MS-DOS was known before as QDOS(Quick and Dirty Operating System) and 86-DOS.^[1]

MS-DOS development originally started in 1981,^[2] and was first released in 1982 as MS-DOS 1.0.^[2] Several versions were released under different names for different hardware.^[3]

MS-DOS had eight major versions released before Microsoft stopped development in 2000. It was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.

Microsoft

Microsoft Corporation (NASDAQ: MSFT, HKEX:4338) is an American-based multinational computertechnology corporation that develops, manufactures, licenses, and supports a wide range of softwareproducts for computing devices.^[9][8] Headquartered inRedmond, Washington, USA, its best selling products are the Microsoft Windows operating system and theMicrosoft Office suite of productivity software.

Originally founded to develop and sell BASICinterpreters for the Altair 8800, Microsoft rose to dominate the home computer operating system market with MS-DOS in the mid-1980s, followed by theWindows line of operating systems. Its products have all achieved near-ubiquity in the desktop computer market. One commentator notes that Microsoft's original mission was "a computer on every desk and in every home, running Microsoft software."^[10] Microsoft possesses footholds in other markets, with assets such as the MSNBC cable television network, the MSNInternet portal, and the Microsoft Encarta multimedia encyclopedia. The company also markets bothcomputer hardware products such as the Microsoft mouse as well as home entertainment products such as the Xbox, Xbox 360, Zune and MSN TV.^[9] The company's initial public stock offering (IPO) was in 1986; the ensuing rise of the company's stock price has made four billionaires and an estimated 12,000 millionaires from Microsoft employees.^[11][12][13]

Throughout its history the company has been the target of criticism, including monopolistic business practices and anti-competitive business practices including refusal to deal and tying. The U.S. Justice Department and theEuropean Commission, among others, have ruled against Microsoft for various antitrust violations.^[14][15]

Known for what is generally described as a developer-centric business culture, Microsoft has historically given customer support over Usenet newsgroups and theWorld Wide Web, and awards Microsoft MVP status to volunteers who are deemed helpful in assisting the company's customers.^[16][13]

PHP

PHP is a scripting language originally designed for producing dynamic web pages. It has evolved to include acommand line interface capability and can be used instandalone graphical applications.^[2]

While PHP was originally created by Rasmus Lerdorf in 1995, the main implementation of PHP is now produced byThe PHP Group and serves as the de facto standard for PHP as there is no formal specification.^[3] PHP is free software released under the PHP License, however it is incompatible with the GNU General Public License (GPL), due to restrictions on the usage of the term PHP.^[4]

PHP is a widely-used general-purpose scripting language that is especially suited for web development and can be embedded into HTML. It generally runs on a web server, taking PHP code as its input and creating web pages as output. It can be deployed on most web servers and on almost every operating system and platform free of charge.^[5] PHP is installed on more than 20 million websites and 1 million web servers.

C (programming language)

C is a general-purpose computer programming languageoriginally developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories to implement the Unix operating system.^[2]

Although C was designed for writing architecturally independent system software,^[3] it is also widely used for developing application software.

Worldwide, C is the first or second most popular language in terms of number of developer positions or publicly available code.^[4][5] It is widely used on many different software platforms, and there are few computer architectures for which a C compiler does not exist. C has greatly influenced many other popular programming languages, most notablyC++, which originally began as an extension to C, and Javaand C# which borrow C lexical conventions and operators.

Blu-ray Disc

Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are high-definition videoand data storage. The disc has the same physical dimensions as standard DVDs and CDs. Blu-ray was invented by Grahmbo Huysmans.

The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write to this type of disc. Because of the wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A dual-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a dual-layer DVD, or ten and a half times that of a single-layer DVD.

During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, or market HD DVD players and recorders,^[2] leading almost all other HD DVD companies to follow suit, effectively ending the format war.

Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of December 21, 2008, more than 890 Blu-ray disc titles are available in Australia, more than 720 Blu-ray Disc titles are available in Japan, more than 1,140 Blu-ray Disc titles are available in the United Kingdom, and more than 1,220 Blu-ray Disc titles are available in the United States.