Personal computer
From ECDL.web
A personal computer (PC) is a microcomputer whose price, size, and capabilities make it useful for individuals. The term was popularized by Apple with the Apple II in the late-1970s and early-1980s, and afterwards by IBM with the IBM Personal Computer. Personal computers are also known as home computers.
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[edit] History
Main article: History of computing hardware (1960s-present)
[edit] Mainframes and large minicomputers
Before the advent of the microprocessor in the early 1970s, computers were generally large, costly systems owned by universities, government agencies, and similar-sized institutions. End users often did not directly interact with the machine but instead would prepare tasks for the computer on off-line equipment, such as card punches. A number of assignments for the computer would be gathered up and processed in batch mode. After the job had completed, users could collect the results. In some cases it could take hours or days between submitting a job to the computing center and receiving the output.
A more interactive form of computer use developed commercially by the middle 1960s. In a time-sharing system, multiple computer terminals let many people share the use of one mainframe computer processor. This was common in business applications and in science and engineering.
A different model of computer use was foreshadowed by the way in which early, pre-commercial, experimental computers were used, where one user had exclusive use of a processor. Some of the first computers that might be called "personal" were early minicomputers such as the LINC and PDP-8, and later on VAX and larger minicomputers from Digital Equipment Corporation (DEC), Data General, Prime Computer, and others. By today's standards they were very large (about the size of a refrigerator) and cost prohibitive (typically tens of thousands of US dollars), and thus were rarely purchased by an individual. However, they were much smaller, less expensive, and generally simpler to operate than many of the mainframe computers of the time. Therefore, they were accessible for individual laboratories and research projects. Minicomputers largely freed these organizations from the batch processing and bureaucracy of a commercial or university computing center.
In addition, minicomputers were relatively interactive and soon had their own operating systems. The minicomputer Xerox Alto (1973) was a landmark step in the development of personal computers, because of its graphical user interface, bit-mapped high resolution screen, large internal and external memory storage, mouse, and special software. The minicomputer era was an intermediary step from mainframes to personal computer usage.
Minicomputers were available to smaller organizations than those that once used mainframes, but were not aimed at individuals, Ken Olsen, founder of DEC, has been widely quoted as saying in 1971 "I can think of no reason why an individual would want to own a computer." This was understandable, considering what DEC was offering: only a fairly large organization could use or afford a machine the size of an average home refrigerator that required external terminals to operate and program. A few individuals, such as [Steve Wozniak], had differing views, as will be seen below.
[edit] Computers at home
The minicomputer ancestors of the modern personal computer did not use microprocessors, which explained their size and high cost. After the commercialization of the "computer-on-a-chip", the cost of manufacture of a computer system dropped dramatically. The arithmetic, logic, and control functions that previously occupied several costly circuit boards were now available in one integrated circuit (one chip). Concurrently, advances in the development of solid state memory eliminated the bulky, costly, and power-hungry magnetic core memory used in prior generations of computers.
There were a few researchers at places like SRI and Xerox PARC who were working on computers that a single person could use and could be connected by fast, versatile networks: not home computers, but personal ones. Olsen did not ask them, because minicomputers were still selling.
A programmable terminal called the Datapoint 2200 is the earliest known device that bears any significant resemblance to the modern personal computer. It was made by CTC (now known as Datapoint) in 1970 and was a complete system in a small case bearing the approximate footprint of an IBM Selectric typewriter. The system's CPU was constructed from a variety of discrete components, although the company had commissioned Intel to develop a single-chip processing unit; there was a falling out between CTC and Intel, and the chip Intel had developed wasn't used. Intel soon released a modified version of that chip as the Intel 8008, the world's first 8-bit microprocessor. The needs and requirements of the Datapoint 2200 therefore determined the nature of the 8008, upon which all successive processors used in IBM-compatible PCs were based. Additionally, the design of the Datapoint 2200's multi-chip CPU and the final design of the Intel 8008 were so similar that the two are largely software-compatible; therefore, the Datapoint 2200, from a practical perspective, can be regarded as if it were indeed powered by an 8008, which makes it a strong candidate for the title of "first microcomputer" as well.
Development of the single-chip microprocessor was an enormous catalyst to the popularization of cheap, easy to use, and truly personal computers. The w:Altair 8800, introduced in a Popular Electronics magazine article in the December 1974 issue, at the time set a new low price point for a computer, bringing computer ownership to an admittedly select market in the 1970s. This was followed by the IMSAI 8800 computer, with similar abilities and limitations. The Altair and IMSAI were essentially scaled-down minicomputers and were incomplete: to connect a keyboard or screen to them required heavy, expensive "peripherals". These machines both featured a front panel with switches and lights, which communicated with the operator in binary. To program the Machine, one didn't simply power up: one first had to key in the bootstrap loader program in binary, then read in a paper tape containing a BASIC interpreter, using a massive paper-tape reader. Keying the loader required setting a bank of eight switches up or down and pressing the "load" button, once for each byte of the program, which was typically hundreds of bytes long. This was before one could begin to do anything
It was arguably the Altair computer that spawned the development of Apple, as well as Microsoft, spawning the Altair BASIC programming language interpreter, Microsoft's first product. The second generation of microcomputers — those that appeared in the late 1970s, sparked by the success of the Steve Wozniak-designed Apple release, the Apple II — were usually known as home computers. For business use these systems were less capable and in some ways less versatile than the large business computers of the day. They were designed for fun and educational purposes, not so much for practical use. And although you could use some simple office/productivity applications on them, they were generally used by computer enthusiasts for learning to program and for running computer games, for which the personal computers of the period were less suitable and much too expensive. For the more technical hobbyists home computers were also used for electronics interfacing, such as controlling model railroads, and other general hobbyist pursuits. By the late 1990s, "home computers" were slowly being replaced by "personal computers" because the graphics and sound capacities of "home" systems were matched by those intended for "business" purposes. This, combined with a general decrease in costs of personal computers, caused the two market segments to fuse. These computers were pre-assembled, often pre-configured with bundled software, and required little technical knowledge to operate.
A 1978 ad for the Apple II used the wording "Apple, the personal computer". There was no trademark symbol. Three years later, the term "personal computer" was a trademark of IBM, which had decided to invade Apple's turf and had done it successfully; a few years later, a judge declared that "personal computer" was no longer an IBM trademark, but a generic term for any personal computer not made by Apple. A cynic once said: "Apple never misses an opportunity to miss an opportunity." Ironically, in 1997, a leading computer magazine declared that Apple's new iMac computer was the best-selling personal computer on the market, with nearly 10% market share. The magazine printed a list of computers by several different manufacturers, in order of sales volume: they were not separated by operating system, despite fact that in that year very few retailers displayed IBM PC's and Macintosh computers side by side.
[edit] Today
During the 1990s, the power of personal computers increased radically, blurring the formerly sharp distinction between personal computers and multi-user computers, such as mainframes. Today higher-end computers often distinguish themselves from personal computers by greater reliability or greater ability to multitask, rather than by brute CPU ability.
In today's common usage, personal computer and PC usually indicate an IBM PC compatible. Due to this association, some manufacturers of personal computers that are not IBM PCs avoid explicitly using the terms to describe their products.
Due to networks, the Internet and such factors as digital rights management, modern personal computers are no longer the exclusive tools of their users. Support of desktop computers in business now requires as much bureaucracy and professional training as did operating a time-sharing system, with the drawback of much lower security and many users skilled enough to get into trouble but not skilled enough to get out.
[edit] Uses
Personal computers are normally operated by one user at a time to perform such general purpose tasks as word processing, Internet browsing, Internet faxing, e-mail and other digital messaging, multimedia playback, computer game play, computer programming, etc. The user of a modern personal computer may have significant knowledge of the operating environment and application programs, but is not necessarily interested in programming nor even able to write programs for the computer. Therefore, most software written primarily for personal computers tends to be designed with simplicity of use, or "user-friendliness" in mind. However, the software industry continuously provide a wide range of new products for use in personal computers, targeted at both the expert and the non-expert user.
[edit] Configuration
Main article: Main parts of a personal computer
Personal computers can be categorized by size and portability:
- Desktop computers
- Laptop or notebook computers
- Personal digital assistants (PDAs)
- Portable computers
- Tablet computers
- Wearable computers
[edit] Laptop computers
Main article: Laptop
A laptop computer or simply laptop, also called a notebook computer or notebook, is a small personal computer designed for mobility. Usually all of the interface hardware needed to operate the laptop, such as parallel and serial ports, graphics card, sound channel, etc., are built in to a single unit. Most laptops contain batteries to facilitate operation without a readily available electrical outlet. In the interest of saving power, weight and space, they usually share RAM with the video channel, slowing their performance compared to an equivalent desktop machine.
[edit] Non IBM-compatible personal computers
Though many personal computers are compatible with IBM PCs using either Microsoft Windows or Unix-like operating systems such as Linux, a number of other personal computer types are also popular. Note that in many regions, in popular usage the term "PC", though simply short for "personal computer", has become synonymous with "IBM PC–compatible."
An alternative to the IBM-compatible PC is the Macintosh (thus the commonly heard comparative, "PC vs. Mac"). The Macintosh originally used the Motorola 68000 series, then shifted to the IBM and Motorola PowerPC processors. This makes the term “IBM-compatible” particularly ironic, since the Macintosh was powered by an IBM chip, though neither IBM PCs nor so-called “IBM-compatibles” were.
In January, 2006, Apple shifted its architecture to the same Intel processor family found in many so-called “IBM-compatibles.”