A computer is a machine that manipulates data according to a set of instructions.
Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century (1940C1945). These were the size of a large room, consuming as much power as several hundred modern personal computers (PCs). Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space. Simple computers are small enough to fit into a wristwatch, and can be powered by a watch battery. Personal computers in their various forms are icons of the Information Age and are what most people think of as computers. The embedded computers found in many devices from MP3 players to fighter aircraft and from toys to industrial robots are however the most numerous.
The ability to store and execute lists of instructions called programs makes computers extremely versatile, distinguishing them from calculators. The ChurchCTuring 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. Therefore computers ranging from a mobile phone to a supercomputer are all able to perform the same computational tasks, given enough time and storage capacity.
Programming languages provide various ways of specifying programs for computers to run. Unlike natural languages, programming languages are designed to permit no ambiguity and to be concise. They are purely written languages and are often difficult to read aloud. They are generally either translated into machine code by a compiler or an assembler before being run, or translated directly at run time by an interpreter. Sometimes programs are executed by a hybrid method of the two techniques. There are thousands of different programming languages―some intended to be general purpose, others useful only for highly specialized applications.
Computers have been used to coordinate information between multiple locations since the 1950s. The U.S. military's SAGE system was the first large-scale example of such a system, which led to a number of special-purpose commercial systems like Sabre.
In the 1970s, computer engineers at research institutions throughout the United States began to link their computers together using telecommunications technology. This effort was funded by ARPA (now DARPA), and the computer network that it produced was called the ARPANET. The technologies that made the Arpanet possible spread and evolved.
In time, the network spread beyond academic and military institutions and became known as the Internet. The emergence of networking involved a redefinition of the nature and boundaries of the computer. Computer operating systems and applications were modified to include the ability to define and access the resources of other computers on the network, such as peripheral devices, stored information, and the like, as extensions of the resources of an individual computer. Initially these facilities were available primarily to people working in high-tech environments, but in the 1990s the spread of applications like e-mail and the World Wide Web, combined with the development of cheap, fast networking technologies like Ethernet and ADSL saw computer networking become almost ubiquitous. In fact, the number of computers that are networked is growing phenomenally. A very large proportion of personal computers regularly connect to the Internet to communicate and receive information. Wireless networking, often utilizing mobile phone networks, has meant networking is becoming increasingly ubiquitous even in mobile computing environments.
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.
电脑是一台操纵根据指令集的数据。
虽然电脑机械事例，通过记录的人类历史上存在很多，首先开发了电脑在20世纪中期（1940年至45年）。这是一个大房间的大小，功耗一样，数百现代（PC）的个人电脑。关于集成电路的现代计算机的倍比早期的机器能够十亿百万美元，占据空间小部分。简单的电脑足够小，能够装到手表，并且可以通过手表电池供电。在各种形式的个人电脑是信息时代的图标，并且大多数人认为是“电脑”。在嵌入式设备中发现的许多MP3播放器到战斗机，从玩具到工业机器人的电脑但最多。
能够存储并执行指令的列表称为程序使电脑非常多才多艺，他们的区别计算器。教会-图灵论题是这种多功能性的数学声明：任何一个有某些最低限度的能力的电脑上，原则上执行相同的任务，任何其他电脑可以执行的能力。因此，从电脑手机到超级电脑都能够完成同样的计算任务，足够的时间和存储容量。
编程语言提供了指定的电脑程序运行的各种方法。与自然语言，编程语言的目的是不允许任何含糊和精简。它们是纯粹的语言文字，而且往往难以朗读。他们一般都翻译成机器代码编译器或汇编程序运行之前，或翻译，直接在运行时由一名翻译的时间。有时候程序执行的是两种方法混合方法。有许多不同的编程语言成千上万的一些拟通用，其他人只需要高度专业化的应用非常有用。
电脑被用来协调20世纪50年代以来，在多个地点的资料。美国军方的SAGE系统是第一个大规模实施这些制度，这导致了特殊用途的军刀等商业系统的数量规模的例子。
在20世纪70年代，在研究机构的电脑工程师在美国开始他们的计算机连接在一起使用电信技术。这一努力是ARPA的资助（现在DARPA）的，以及计算机网络，它被称为产生了ARPANET。该技术取得了ARPANET可能扩散和演变。
随着时间的推移，以后的学术和军事机构网络化，成为称为电脑互联网。网络的出现，涉及的性质和计算机边界的重新定义。计算机操作系统和应用程序进行了修改，包括能够定义和访问网络上的资源，如其他计算机外围设备，存储的信息，等等，为扩展名的个人电脑上的资源。开始时，这些设施主要是人们可以在高科技环境中工作，但在20世纪90年代申请的蔓延，如电子邮件和万维网，与发展经济结合起来，如以太网和ADSL网络技术的快速看到电脑联网变得几乎无处不在。事实上，该是联网的计算机数量正在飘洋过海。个人电脑的一个非常大的比例，定期连接到互联网来进行交流和接收信息。 “无线”网络，往往利用移动电话网络，意味着网络正在成为即使在移动计算环境日益普及。
对于电脑需要很好地协同工作，并能够交换信息促成了许多标准组织，俱乐部和双方正式和非正式性的社会需要。