The fundamental concept of storing programs in the computer's memory alongside the data they operate on is the crux of the von Neumann, or stored program, architecture.
A general purpose computer has four main sections: The arithmetic and logic unit (ALU), the control unit, the memory, and the input and output devices (collectively termed I/O).
Many computers include some instructions that may only be partially interpreted by the control system and partially interpreted by another device.
In 1837, the archbishop of Cologne Clemens August von Droste-Vischering was arrested and imprisoned for two years after a dispute over the legal status of marriages between Protestants and Roman Catholics.
The control unit (often called a control system or central controller) directs the various components of a computer.
Some computers may divide their work between one or more separate CPUs, creating a multiprocessing configuration.
Modern desktop computers contain many smaller computers that assist the main CPU in performing I/O.
Vacuum tube-based computers were in use throughout the 1950s, but were largely replaced in the 1960s by transistor-based devices, which were smaller, faster, cheaper, used less power and were more reliable.
Computer main memory comes in two principal varieties: Random access memory or RAM and read-only memory or ROM.
Modern von Neumann computers display some traits of the Harvard architecture in their designs, such as in CPU caches.
The very definition of a computer has changed and it is therefore impossible to identify the first computer.
Embedded computers are small, simple devices that are often used to control other devices—for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and even children's toys.
The Church–Turing thesis is a mathematical statement of this versatility: Any computer with a certain minimum capability is, in principle, capable of performing the same tasks that any other computer can perform.
The ability to store and execute programs makes computers extremely versatile and distinguishes them from calculators.
Input/output (I/O) is the means by which a computer receives information from the outside world and sends results back.
Once told to run this program, the computer will perform the repetitive addition task without further human intervention.
Computer hardware may fail or may itself have a fundamental problem that produces unexpected results in certain situations.
Often, I/O devices are complex computers in their own right with their own CPU and memory.
The term hardware covers all of those parts of a computer that are tangible objects.
That is to say that a list of instructions (the program) can be given to the computer and it will store them and carry them out at some time in the future.
One means by which this is done is with a special signal called an interrupt which can periodically cause the computer to stop executing instructions where it was and do something else instead.
Supercomputers usually see usage in large-scale simulation, graphics rendering, and cryptography applications.
Converting programs written in assembly language into something the computer can actually understand (machine language) is usually done by a computer program called an assembler.
The need for computers to work well together and to be able to exchange information has spawned the need for many standards organizations, clubs and societies of both a formal and informal nature.
ROM is typically used to store the computer's initial start-up instructions.
The emergence of networking involved a redefinition of the nature and boundaries of the computer.
Software refers to parts of the computer that have no material form; programs, data, protocols, etc are all software.
Before the era of cheap computers, the principle use for multitasking was to allow many people to share the same computer.
Graphics processors and computers with SIMD and MIMD features often provide ALUs that can perform arithmetic on vectors and matrices.
Programming languages provide various ways of specifying programs for computers to run.
A typical modern computer can execute billions of instructions every second and nearly never make a mistake over years of operation.
Seemingly, multitasking would cause a computer that is switching between several programs to run more slowly—in direct proportion to the number of programs it is running.
By this standard, many earlier devices would no longer be called computers by today's definition, but are usually referred to as such in their historical context.
On the other hand, a computer may be programmed to do this with just a few simple instructions.
The simplest computers are able to perform any of a handful of different instructions, the more complex computers have several hundred to choose from—each with a unique numerical code.
Supercomputers in particular often have highly unique architectures that differ significantly from the basic stored-program architecture and from general purpose computers.
A very large proportion of personal computers regularly connect to the Internet to communicate and receive information.
High level languages are usually "compiled" into machine language (or sometimes into assembly language and then into machine language) using another computer program called a compiler.
On a typical personal computer, peripherals include inputs like the keyboard and mouse, and outputs such as the display and printer.
A computer can store any kind of information in memory as long as it can be somehow represented in numerical form.
Society has come to recognize personal computers and their portable equivalent, the laptop computer, as icons of the information age; they are what most people think of as "a computer."
The defining feature of modern computers which distinguishes them from all other machines is that they can be programmed.
Originally, the term "computer" referred to a person who performed numerical calculations (a human computer), often with the aid of a mechanical calculating device.
A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features that are seen in modern computers.
Bugs are usually not the fault of the computer.
Superscalar computers contain multiple ALUs so that they can process several instructions at the same time.
Machine languages and the assembly languages that represent them (collectively termed low-level programming languages) tend to be unique to a particular type of computer.
A computer is a machine for manipulating data according to a list of instructions.
The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.
The control system decodes each instruction and turns it into a series of control signals that operate the other parts of the computer.
The design made the universal computer a practical reality.
Many computers directly support subroutines by providing a type of jump that "remembers" the location it jumped from and another instruction to return to that point.
Modern computers have billions or even trillions of bytes of memory.
In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte).
Many devices once called "computers" would no longer qualify as such by today's standards.
A number of projects to develop computers based on the stored program architecture commenced around this time, the first of these being completed in Great Britain.
Traditionally, this technique was utilized only in large and powerful computers such as supercomputers, mainframe computers and servers.
A graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3D graphics.
Large computer programs may take teams of computer programmers years to write and the probability of the entire program having been written completely in the manner intended is unlikely.
By the 1980s, computers had become sufficiently small and cheap to replace simple mechanical controls in domestic appliances such as washing machines.
Similarly, a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met.
Instructions that modify the program counter are often known as "jumps" and allow for loops (instructions that are repeated by the computer) and often conditional instruction execution (both examples of control flow).
Nearly all modern computers implement some form of the stored program architecture, making it the single trait by which the word "computer" is now defined.
During the first half of the twentieth century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation.
A computer's memory can be viewed as a list of cells into which numbers can be placed or read.
Letters, numbers, even computer instructions can be placed into memory with equal ease.
Around the same time, computers became widely accessible for personal use by individuals in the form of home computers and the now ubiquitous personal computer.
Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers.
turtle graphics - Computer Definition. A method for creating graphic images in the Logo programming language. The "turtle" is an imaginary pen that is given drawing commands, such as go forward and turn right. On screen, the turtle is shaped like a triangle. See Logo.
There is no standard computer keyboard, although many manufacturers imitate the keyboard of PCs. There are actually three different PC keyboards: the original PC keyboard with 84 keys, the AT keyboard also with 84 keys and the enhanced keyboard with 101 keys.
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