1.
Calculator
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An electronic calculator is a small, portable electronic device used to perform operations ranging from basic arithmetic to complex mathematics. The first solid state electronic calculator was created in the 1960s, building on the history of tools such as the abacus. It was developed in parallel with the computers of the day. The pocket sized devices became available in the 1970s, especially after the first microprocessor and they later became used commonly within the petroleum industry. Modern electronic calculators vary, from cheap, give-away, credit-card-sized models to sturdy desktop models with built-in printers and they became popular in the mid-1970s. By the end of decade, calculator prices had reduced to a point where a basic calculator was affordable to most. In addition to general purpose calculators, there are designed for specific markets. For example, there are scientific calculators which include trigonometric and statistical calculations, some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, as of 2016, basic calculators cost little, but the scientific and graphing models tend to cost more. In 1986, calculators still represented an estimated 41% of the worlds general-purpose hardware capacity to compute information, by 2007, this diminished to less than 0. 05%. Modern 2016 electronic calculators contain a keyboard with buttons for digits and arithmetical operations, most basic calculators assign only one digit or operation on each button, however, in more specific calculators, a button can perform multi-function working with key combinations. Large-sized figures and comma separators are used to improve readability. Various symbols for function commands may also be shown on the display, fractions such as 1⁄3 are displayed as decimal approximations, for example rounded to 0.33333333. Also, some fractions can be difficult to recognize in decimal form, as a result, Calculators also have the ability to store numbers into computer memory. Basic types of these only one number at a time. The variables can also be used for constructing formulas, some models have the ability to extend memory capacity to store more numbers, the extended memory address is termed an array index. Power sources of calculators are, batteries, solar cells or mains electricity, some models even have no turn-off button but they provide some way to put off. Crank-powered calculators were also common in the computer era
2.
Computer science
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Computer science is the study of the theory, experimentation, and engineering that form the basis for the design and use of computers. An alternate, more succinct definition of science is the study of automating algorithmic processes that scale. A computer scientist specializes in the theory of computation and the design of computational systems and its fields can be divided into a variety of theoretical and practical disciplines. Some fields, such as computational complexity theory, are highly abstract, other fields still focus on challenges in implementing computation. Human–computer interaction considers the challenges in making computers and computations useful, usable, the earliest foundations of what would become computer science predate the invention of the modern digital computer. Machines for calculating fixed numerical tasks such as the abacus have existed since antiquity, further, algorithms for performing computations have existed since antiquity, even before the development of sophisticated computing equipment. Wilhelm Schickard designed and constructed the first working mechanical calculator in 1623, in 1673, Gottfried Leibniz demonstrated a digital mechanical calculator, called the Stepped Reckoner. He may be considered the first computer scientist and information theorist, for, among other reasons and he started developing this machine in 1834, and in less than two years, he had sketched out many of the salient features of the modern computer. A crucial step was the adoption of a card system derived from the Jacquard loom making it infinitely programmable. Around 1885, Herman Hollerith invented the tabulator, which used punched cards to process statistical information, when the machine was finished, some hailed it as Babbages dream come true. During the 1940s, as new and more powerful computing machines were developed, as it became clear that computers could be used for more than just mathematical calculations, the field of computer science broadened to study computation in general. Computer science began to be established as an academic discipline in the 1950s. The worlds first computer science program, the Cambridge Diploma in Computer Science. The first computer science program in the United States was formed at Purdue University in 1962. Since practical computers became available, many applications of computing have become distinct areas of study in their own rights and it is the now well-known IBM brand that formed part of the computer science revolution during this time. IBM released the IBM704 and later the IBM709 computers, still, working with the IBM was frustrating if you had misplaced as much as one letter in one instruction, the program would crash, and you would have to start the whole process over again. During the late 1950s, the science discipline was very much in its developmental stages. Time has seen significant improvements in the usability and effectiveness of computing technology, modern society has seen a significant shift in the users of computer technology, from usage only by experts and professionals, to a near-ubiquitous user base
3.
Graphical user interface
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GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces, which require commands to be typed on a computer keyboard. The actions in a GUI are usually performed through direct manipulation of the graphical elements, beyond computers, GUIs are used in many handheld mobile devices such as MP3 players, portable media players, gaming devices, smartphones and smaller household, office and industrial controls. Designing the visual composition and temporal behavior of a GUI is an important part of application programming in the area of human–computer interaction. Its goal is to enhance the efficiency and ease of use for the logical design of a stored program. Methods of user-centered design are used to ensure that the language introduced in the design is well-tailored to the tasks. The visible graphical interface features of an application are sometimes referred to as chrome or GUI, typically, users interact with information by manipulating visual widgets that allow for interactions appropriate to the kind of data they hold. The widgets of an interface are selected to support the actions necessary to achieve the goals of users. A model–view–controller allows a structure in which the interface is independent from and indirectly linked to application functions. This allows users to select or design a different skin at will, good user interface design relates to users more, and to system architecture less. Large widgets, such as windows, usually provide a frame or container for the main presentation content such as a web page, smaller ones usually act as a user-input tool. A GUI may be designed for the requirements of a market as application-specific graphical user interfaces. By the 1990s, cell phones and handheld game systems also employed application specific touchscreen GUIs, newer automobiles use GUIs in their navigation systems and multimedia centers, or navigation multimedia center combinations. Sample graphical desktop environments A GUI uses a combination of technologies and devices to provide a platform that users can interact with, a series of elements conforming a visual language have evolved to represent information stored in computers. This makes it easier for people with few computer skills to work with, the most common combination of such elements in GUIs is the windows, icons, menus, pointer paradigm, especially in personal computers. The WIMP style of interaction uses a virtual device to represent the position of a pointing device, most often a mouse. Available commands are compiled together in menus, and actions are performed making gestures with the pointing device, a window manager facilitates the interactions between windows, applications, and the windowing system. The windowing system handles hardware devices such as pointing devices, graphics hardware, window managers and other software combine to simulate the desktop environment with varying degrees of realism. Smaller mobile devices such as personal assistants and smartphones typically use the WIMP elements with different unifying metaphors, due to constraints in space
4.
Dialog box
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The graphical control element dialog box is a small window that communicates information to the user and prompts them for a response. Dialog boxes are classified as modal or modeless, depending on whether they block interaction with the software that initiated the dialog, the type of dialog box displayed is dependent upon the desired user interaction. An example of a box is the about box found in many software programs, which usually displays the name of the program, its version number. Non-modal or modeless dialog boxes are used when the information is not essential to continue. In general, good software design calls for dialogs to be of this type where possible, an example might be a dialog of settings for the current document, e. g. the background and text colors. The user can continue adding text to the main window whatever color it is, usability practitioners generally regard modal dialogs as bad design-solutions, since they are prone to produce mode errors. Dangerous actions should be undoable wherever possible, a modal alert dialog that appears unexpectedly or which is dismissed automatically will not protect from the dangerous action, a modal dialog interrupts the main workflow. This effect has either been sought by the developer because it focuses on the completion of the task at hand or rejected because it prevents the user from changing to a different task when needed. The concept of a document modal dialog has recently used, most notably in OS X. In the first case, they are shown as sheets attached to a parent window and these dialogs block only that window until the user dismisses the dialog, permitting work in other windows to continue, even within the same application. In OS X, dialogs appear to emanate from a slot in their parent window and this helps to let the user understand that the dialog is attached to the parent window, not just shown in front of it. The OS X dialog box blocks the parent window, preventing the user from referring to it while interacting with the dialog and this may require the user to close the dialog to access the necessary information, then re-open the dialog box to continue
5.
Hard disk drive
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The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a manner, meaning that individual blocks of data can be stored or retrieved in any order. HDDs are a type of storage, retaining stored data even when powered off. Introduced by IBM in 1956, HDDs became the dominant secondary storage device for computers by the early 1960s. Continuously improved, HDDs have maintained this position into the era of servers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Seagate, Toshiba, as of 2016, HDD production is growing, although unit shipments and sales revenues are declining. While SSDs have higher cost per bit, SSDs are replacing HDDs where speed, power consumption, small size, the primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000, the two most common form factors for modern HDDs are 3. 5-inch, for desktop computers, and 2. 5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA, SATA, Hard disk drives were introduced in 1956, as data storage for an IBM real-time transaction processing computer and were developed for use with general-purpose mainframe and minicomputers. The first IBM drive, the 350 RAMAC in 1956, was approximately the size of two medium-sized refrigerators and stored five million six-bit characters on a stack of 50 disks. In 1962 the IBM350 RAMAC disk storage unit was superseded by the IBM1301 disk storage unit, cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches above the platter surface. Motion of the head array depended upon a binary system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes, access time was about a quarter of a second. Also in 1962, IBM introduced the model 1311 disk drive, users could buy additional packs and interchange them as needed, much like reels of magnetic tape. Later models of removable pack drives, from IBM and others, became the norm in most computer installations, non-removable HDDs were called fixed disk drives. Some high-performance HDDs were manufactured with one head per track so that no time was lost physically moving the heads to a track, known as fixed-head or head-per-track disk drives they were very expensive and are no longer in production. In 1973, IBM introduced a new type of HDD code-named Winchester and its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. Instead, the heads were allowed to land on an area of the disk surface upon spin-down
6.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
7.
Personal computer hardware
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Computer hardware is the collection of physical components that constitute a computer system. By contrast, software is instructions that can be stored and run by hardware, hardware is directed by the software to execute any command or instruction. A combination of hardware and software forms a usable computing system, the template for all modern computers is the Von Neumann architecture, detailed in a 1945 paper by Hungarian mathematician John von Neumann. The meaning of the term has evolved to mean a stored-program computer in which an instruction fetch and this is referred to as the Von Neumann bottleneck and often limits the performance of the system. For the third year, U. S. business-to-business channel sales increased. The impressive growth was the fastest sales increase since the end of the recession, sales growth accelerated in the second half of the year peaking in fourth quarter with a 6.9 percent increase over the fourth quarter of 2012. There are a number of different types of system in use today. The personal computer, also known as the PC, is one of the most common types of computer due to its versatility, laptops are generally very similar, although they may use lower-power or reduced size components, thus lower performance. The computer case is a plastic or metal enclosure that houses most of the components, a case can be either big or small, but the form factor of motherboard for which it is designed matters more. A power supply unit converts alternating current electric power to low-voltage DC power for the components of the computer. Laptops are capable of running from a battery, normally for a period of hours. The motherboard is the component of a computer. It is usually cooled by a heatsink and fan, or water-cooling system, most newer CPUs include an on-die Graphics Processing Unit. The clock speed of CPUs governs how fast it executes instructions, many modern computers have the option to overclock the CPU which enhances performance at the expense of greater thermal output and thus a need for improved cooling. The chipset, which includes the bridge, mediates communication between the CPU and the other components of the system, including main memory. Random-Access Memory, which stores the code and data that are being accessed by the CPU. For example, when a web browser is opened on the computer it takes up memory, RAM usually comes on DIMMs in the sizes 2GB, 4GB, and 8GB, but can be much larger. Read-Only Memory, which stores the BIOS that runs when the computer is powered on or otherwise begins execution, the BIOS includes boot firmware and power management firmware
8.
Usability
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Usability is the ease of use and learnability of a human-made object such as a tool or device. The object of use can be an application, website, book, tool, machine, process, vehicle. A usability study may be conducted as a job function by a usability analyst or as a secondary job function by designers, technical writers, marketing personnel. It is widely used in electronics, communication, and knowledge transfer objects. Usability includes methods of measuring usability, such as needs analysis, in human-computer interaction and computer science, usability studies the elegance and clarity with which the interaction with a computer program or a web site is designed. Usability differs from user satisfaction and user experience because usability does not directly consider usefulness or utility, by understanding and researching the interaction between product and user, the usability expert can also provide insight that is unattainable by traditional company-oriented market research. For example, after observing and interviewing users, the usability expert may identify needed functionality or design flaws that were not anticipated, a method called contextual inquiry does this in the naturally occurring context of the users own environment. In the user-centered design paradigm, the product is designed with its users in mind at all times. In the user-driven or participatory design paradigm, some of the users become actual or de facto members of the design team, the term user friendly is often used as a synonym for usable, though it may also refer to accessibility. Usability describes the quality of experience across websites, software, products. There is no consensus about the relation of the terms ergonomics, some think of usability as the software specialization of the larger topic of ergonomics. Others view these topics as tangential, with focusing on physiological matters. Usability is also important in website development, according to Jakob Nielsen, Studies of user behavior on the Web find a low tolerance for difficult designs or slow sites. And they dont want to learn how to use a home page, theres no such thing as a training class or a manual for a Web site. People have to be able to grasp the functioning of the immediately after scanning the home page—for a few seconds at most. Otherwise, most casual users simply leave the site and browse or shop elsewhere, ISO defines usability as The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use. The word usability also refers to methods for improving ease-of-use during the design process, efficiency, Once users have learned the design, how quickly can they perform tasks. Memorability, When users return to the design after a period of not using it, errors, How many errors do users make, how severe are these errors, and how easily can they recover from the errors
