Kiến thức căn bản về computer

Unit 3: Personal computer
I. What is a personal computer?
A personal computer (PC) is a computer whose original sales price, size, and capabilities make it useful for individuals.
It is unknown who coined the phrase with the intent of a small affordable computing device but John W. Mauchly described such a device in a November 3, 1962 New York Times article entitled "Pocket Computer may replace Shopping List". Six years later a manufacturer took a risk at referring to their product this way when Hewlett Packard advertised their "Powerful Computing Genie" as "The New Hewlett Packard 9100A personal computer". This advertisement was too extreme for the target audience and replaced with a much drier ad for the HP 9100A programmable calculator. During the next 7 years the phrase had gained usage so when Byte magazine, published its first edition it referred to its readers as being in the "personal computing field" while Creative Computing defined the personal computer as a "non-(time)shared system containing sufficient processing power and storage capabilities to satisfy the needs of an individual user." Two years later when the 1977 Trinity of preassembled small computers hit the markets, the Apple II and the PET 2001 were advertised as `personal computers` while the TRS-80 was a microcomputer used for household tasks including "personal financial management". By 1979 over half a million microcomputers were sold and the youth of the day had a new concept of the personal computer. The Personal Computer was also the first non-human abstract to be the Time Magazine Person of the Year.
Personal computers can be categorized by size and portability:
Desktop computers
Laptop or notebooks
Personal digital assistants (PDAs)
Portable computers
Tablet computers
Wearable computers
Cell Phones
In their early years personal computer was interchangeable with Microcomputers and home computers. Often, the term "personal computer" is used exclusively for computers running a Microsoft Windows operating system, but this is erroneous. For example, a Macintosh running Mac OS and an IBM PC compatible running GNU/Linux are both personal computers. This confusion stems from the fact that the term "PC" is often used as a shorthand form for "IBM PC compatible" and historically Mac OS has run on non-IBM compatible hardware like the PowerPC architecture. Newer personal computing devices have had their OS wars with WindowsCE struggling with PalmOS in the PDA markets and now the cell phone devices have gotten powerful enough to start a whole new struggle to define the personal computer, its operating system and how we use it in our daily lives.
II. History
1. Mainframes and large minicomputers



Time shared computer terminals connected to central computers, such as the TeleVideo ASCII character mode smart terminal pictured here, were sometimes used before the advent of the PC.
Before the introduction of the microprocessor in the early 1970s, computers were generally large, costly systems owned by large corporations, 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. [10] The minicomputer era was an intermediary step from mainframes to personal computer usage.
2. Computers at home



The 1977 Apple II, one of the 1977 Trinity. Floppy drive pictured a model designed for the Apple III.
One early use of the term "personal computer" appeared in a