computer science, the study ofcomputers and computing, including their theoretical and algorithmic foundations,hardware andsoftware, and their uses for processing information. Thediscipline of computer science includes the study ofalgorithms and data structures, computer andnetwork design, modeling data and information processes, andartificial intelligence. Computer science draws some of its foundations frommathematics andengineering and therefore incorporates techniques from areas such as queueing theory,probability and statistics, andelectronic circuit design. Computer science also makes heavy use ofhypothesis testing and experimentation during the conceptualization, design, measurement, and refinement of newalgorithms, information structures, and computer architectures.

Computer science is considered as part of a family of five separate yet interrelated disciplines: computer engineering, computer science,information systems, informationtechnology, and software engineering. This family has come to be known collectively as the discipline of computing. These fivedisciplines are interrelated in the sense that computing is their object of study, but they are separate since each has its own research perspective and curricular focus. (Since 1991 the Association for Computing Machinery [ACM], the IEEE Computer Society [IEEE-CS], and the Association for Information Systems [AIS] havecollaborated to develop and update thetaxonomy of these five interrelated disciplines and the guidelines that educational institutions worldwide use for their undergraduate, graduate, and research programs.)

The major subfields of computer science include the traditional study ofcomputer architecture,programming languages, and software development. However, they also include computationalscience (the use of algorithmic techniques for modeling scientific data), graphics and visualization, human-computer interaction,databases and information systems, networks, and the social and professional issues that are unique to the practice of computer science. As may be evident, some of these subfields overlap in their activities with other modern fields, such asbioinformatics and computationalchemistry. These overlaps are theconsequence of a tendency among computer scientists to recognize and act upon their field’s many interdisciplinary connections.

Development of computer science

Computer science emerged as an independent discipline in the early 1960s, although the electronicdigital computer that is the object of its study was invented some two decades earlier. The roots of computer science lie primarily in the related fields ofmathematics, electrical engineering,physics, and management information systems.

Mathematics is the source of two key concepts in the development of the computer—the idea that all information can be represented as sequences of zeros and ones and the abstract notion of a “stored program.” In thebinary number system, numbers are represented by a sequence of thebinary digits 0 and 1 in the same way that numbers in the familiardecimal system are represented using the digits 0 through 9. The relative ease with which two states (e.g., high and low voltage) can be realized in electrical andelectronic devices led naturally to thebinary digit, or bit, becoming the basic unit of data storage and transmission in acomputer system.

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Electrical engineering provides the basics of circuit design—namely, the idea that electrical impulses input to a circuit can be combined usingBoolean algebra to produce arbitrary outputs. (The Boolean algebra developed in the 19th century supplied aformalism for designing a circuit with binary input values of zeros and ones [false or true, respectively, in theterminology of logic] to yield any desired combination of zeros and ones as output.) Theinvention of thetransistor and the miniaturization of circuits, along with the invention of electronic, magnetic, and optical media for the storage and transmission of information, resulted from advances in electrical engineering and physics.

Management information systems, originally calleddata processing systems, provided early ideas from which various computer science concepts such as sorting, searching,databases,information retrieval, andgraphical user interfaces evolved. Large corporations housed computers that stored information that was central to the activities of running a business—payroll, accounting, inventory management, production control, shipping, and receiving.

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Theoretical work on computability, which began in the 1930s, provided the neededextension of these advances to the design of whole machines; a milestone was the 1936 specification of theTuring machine (a theoretical computational model that carries out instructions represented as a series of zeros and ones) by the British mathematicianAlan Turing and hisproof of the model’s computational power. Another breakthrough was the concept of thestored-program computer, usually credited to Hungarian American mathematicianJohn von Neumann. These are the origins of the computer science field that later became known asarchitecture and organization.

In the 1950s, most computer users worked either in scientific research labs or in large corporations. The formergroup used computers to help them make complex mathematical calculations (e.g., missile trajectories), while the latter group used computers to manage large amounts ofcorporate data (e.g., payrolls and inventories). Both groups quickly learned that writing programs in themachine language of zeros and ones was not practical or reliable. This discovery led to the development ofassembly language in the early 1950s, which allows programmers to use symbols for instructions (e.g., ADD for addition) and variables (e.g.,X). Another program, known as anassembler, translated these symbolic programs into an equivalent binary program whose steps the computer could carry out, or “execute.”

Othersystem software elements known as linking loaders were developed to combine pieces of assembledcode and load them into the computer’s memory, where they could be executed. Theconcept of linking separate pieces of code was important, since it allowed “libraries” of programs for carrying out common tasks to be reused. This was a first step in the development of the computer science field calledsoftware engineering.

Later in the 1950s, assembly language was found to be so cumbersome that the development of high-level languages (closer to natural languages) began to support easier, faster programming.FORTRAN emerged as the main high-level language for scientific programming, whileCOBOL became the main language for business programming. These languages carried with them the need for different software, calledcompilers, that translate high-level language programs into machine code. As programming languages became more powerful and abstract, building compilers that create high-quality machine code and that are efficient in terms of execution speed and storageconsumption became a challenging computer science problem. The design and implementation of high-level languages is at the heart of the computer science field called programming languages.

Increasing use of computers in the early 1960s provided theimpetus for the development of the firstoperating systems, which consisted of system-resident software that automatically handled input and output and the execution of programs called “jobs.” The demand for better computational techniques led to a resurgence of interest in numerical methods and theiranalysis, an activity that expanded so widely that it became known as computational science.

The 1970s and ’80s saw the emergence of powerfulcomputer graphics devices, both forscientific modeling and other visual activities. (Computerized graphical devices were introduced in the early 1950s with the display of crude images on paper plots andcathode-ray tube [CRT] screens.) Expensive hardware and the limited availability of software kept the field from growing until the early 1980s, when thecomputer memory required forbitmap graphics (in which an image is made up of small rectangular pixels) became more affordable. Bitmap technology, together with high-resolution display screens and the development of graphics standards that make software less machine-dependent, has led to the explosive growth of the field. Support for all these activities evolved into the field of computer science known as graphics and visual computing.

Closely related to this field is the design and analysis of systems that interact directly with users who are carrying out various computational tasks. These systems came into wide use during the 1980s and ’90s, when line-edited interactions with users were replaced bygraphical user interfaces (GUIs). GUI design, which was pioneered byXerox and was later picked up byApple (Macintosh) and finally byMicrosoft (Windows), is important because itconstitutes what people see and do when they interact with a computing device. The design of appropriate user interfaces for all types of users has evolved into the computer science field known as human-computer interaction (HCI).

The field of computer architecture and organization has also evolved dramatically since the first stored-program computers were developed in the 1950s. So called time-sharing systems emerged in the 1960s to allow several users to run programs at the same time from different terminals that were hard-wired to the computer. The 1970s saw the development of the first wide-areacomputer networks (WANs) andprotocols for transferring information at high speeds between computers separated by large distances. As these activities evolved, they coalesced into the computer science field called networking and communications. A major accomplishment of this field was the development of theInternet.

The idea that instructions, as well as data, could be stored in a computer’s memory was critical to fundamental discoveries about the theoretical behavior ofalgorithms. That is, questions such as, “What can/cannot be computed?” have been formally addressed using these abstract ideas. These discoveries were the origin of the computer science field known as algorithms and complexity. A key part of this field is the study and application ofdata structures that are appropriate to different applications.Data structures, along with the development of optimal algorithms for inserting, deleting, and locating data in such structures, are a major concern of computer scientists because they are so heavily used in computer software, most notably in compilers, operating systems, file systems, andsearch engines.

In the 1960s the invention ofmagnetic disk storage provided rapid access to data located at an arbitrary place on the disk. This invention led not only to more cleverly designed file systems but also to the development ofdatabase and information retrieval systems, which later became essential for storing, retrieving, andtransmitting large amounts and wide varieties of data across the Internet. This field of computer science is known as information management.

Another long-term goal of computer science research is the creation of computing machines androbotic devices that can carry out tasks that are typically thought of as requiringhuman intelligence. Such tasks include moving, seeing, hearing, speaking, understanding natural language, thinking, and even exhibitinghuman emotions. The computer science field of intelligent systems, originally known asartificial intelligence (AI), actually predates the firstelectronic computers in the 1940s, although the termartificial intelligence was not coined until 1956.

Three developments in computing in the early part of the 21st century—mobile computing,client-server computing, and computer hacking—contributed to the emergence of three new fields in computer science: platform-based development, parallel anddistributed computing, and security and informationassurance. Platform-based development is the study of the special needs of mobile devices, their operating systems, and their applications. Parallel and distributed computing concerns the development of architectures and programming languages that support the development of algorithms whose components can run simultaneously and asynchronously (rather than sequentially), in order to make better use of time and space. Security and information assurance deals with the design of computing systems and software that protects theintegrity and security of data, as well as the privacy of individuals who are characterized by that data.

Finally, a particular concern of computer science throughout its history is the unique societal impact that accompanies computer science research and technological advancements. With the emergence of the Internet in the 1980s, for example, software developers needed to address important issues related to information security, personal privacy, and system reliability. In addition, the question of whether computer software constitutesintellectual property and the related question “Who owns it?” gave rise to a whole new legal area of licensing and licensing standards that applied to software and relatedartifacts. These concerns and others form the basis of social and professional issues of computer science, and they appear in almost all the other fields identified above.

So, to summarize, the discipline of computer science has evolved into the following 15 distinct fields:

• Algorithms and complexity
• Architecture and organization
• Computational science
• Graphics and visual computing
• Human-computer interaction
• Information management
• Intelligent systems
• Networking and communication
• Operating systems
• Parallel and distributed computing
• Platform-based development
• Programming languages
• Security and information assurance
• Software engineering
• Social and professional issues

Computer science continues to have strong mathematical and engineering roots. Computer science bachelor’s, master’s, and doctoral degree programs are routinely offered by postsecondary academic institutions, and these programs require students to complete appropriate mathematics and engineering courses, depending on their area of focus. For example, all undergraduate computer science majors must study discrete mathematics (logic,combinatorics, and elementarygraph theory). Many programs also require students to complete courses incalculus,statistics,numerical analysis, physics, and principles of engineering early in their studies.